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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretiveDilutiveEffectOfShareIssuancesAndRepurchases_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accretive Dilutive Effect Of Share Issuances And Repurchases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretiveDilutiveEffectOfShareIssuancesAndRepurchases_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accretive (dilutive) effect of share issuances and repurchases.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ComponentManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Component Manufacturing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ComponentManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Component Manufacturing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ComponentManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Component manufacturing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityRemainingUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining unused portion of Credit Facility commitment percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityRemainingUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Remaining Unused Capacity, Commitment Fee Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityRemainingUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, remaining unused capacity, commitment fee percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net unrealized appreciation (depreciation) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Unrealized Appreciation (Depreciation) On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net unrealized appreciation (depreciation) on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFeesPayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income incentive fee payable - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFeesPayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Incentive Fees Payable Due To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFeesPayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Income incentive fees payable due to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AllrediLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Allredi, LLC (fka Marco Group International OpCo, LLC)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AllrediLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Allredi, Llc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AllrediLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Allredi, Llc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3DividendsTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 Dividends Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3DividendsTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Dividends Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3DividendsTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q3 Dividends Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInAccruedInterestAndFeesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued interest and fees payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInAccruedInterestAndFeesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Interest and Fees Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInAccruedInterestAndFeesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in accrued interest and fees payable.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Regular Third Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Regular Third Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Regular Third Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterestRatePercentageBasedOnPriorToCertainConditionsSatisfied_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument interest rate percentage based on prior to certain conditions satisfied.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterestRatePercentageBasedOnPriorToCertainConditionsSatisfied_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Interest Rate Percentage Based on Prior To Certain Conditions Satisfied</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterestRatePercentageBasedOnPriorToCertainConditionsSatisfied_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate prior to certain conditions satisfied</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment interest rate, PIK</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ConsumerProductsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consumer Products Sector</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ConsumerProductsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consumer Products Sector [member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ConsumerProductsSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Consumer Products Sector.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Regular Dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Regular Dividend [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Regular Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring and Nonrecurring [Table]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1SupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q1 Supplemental Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1SupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q1 supplemental second dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfAmountOfPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of amount of pre-incentive fee net investment income</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfAmountOfPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of amount of pre-incentive fee net investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash payments for interest</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HealthcareServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Healthcare Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HealthcareServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Healthcare services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointTwoSixSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">3.267% Fixed Interest Rate</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeniorNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeniorNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Senior Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FiberMaterialsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fiber Materials, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FiberMaterialsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fiber Materials Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FiberMaterialsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fiber Materials, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingEstimateLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Estimate [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of operating segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfOperatingSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Operating Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AppliedDataCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Applied Data Corporation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AppliedDataCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Applied Data Corporation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AppliedDataCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Applied data corporation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmeriwaterLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ameriwater LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmeriwaterLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AmeriWater LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmeriwaterLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">AmeriWater LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfOutstandingCommitmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of outstanding commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfOutstandingCommitmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Outstanding Commitments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfOutstandingCommitmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of outstanding commitments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInReceivablesFromInvestmentsSold_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in receivables from investments sold.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInReceivablesFromInvestmentsSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) In Receivables From Investments Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInReceivablesFromInvestmentsSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Receivables from investments sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares outstanding at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance (in Shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivedFromSmallBusinessAdministrationDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds received from SBA debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivedFromSmallBusinessAdministrationDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds Received from Small Business Administration Debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivedFromSmallBusinessAdministrationDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds received from small business administration debentures.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdditionalInterestRateOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional interest rate on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdditionalInterestRateOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Interest Rate On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdditionalInterestRateOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Additional interest rate on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FishbowlSolutionsLLCRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fishbowl Solutions, LLC - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FishbowlSolutionsLLCRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fishbowl Solutions, LLC Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FishbowlSolutionsLLCRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fishbowl solutions, llc revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureItemAmountsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Affiliate Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Affiliated Issuer [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfResidualInvestmentPorfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of residual investment porfolio companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfResidualInvestmentPorfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Residual Investment Porfolio Companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfResidualInvestmentPorfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of residual investment porfolio companies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Special First Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Special First Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Special First Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment represented more than ten percentage of aggregate investment portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment represented More Than Ten Percentage of Aggregate Investment Portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment represented more than ten percentage of aggregate investment portfolio.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accretion of loan origination fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset, Accretion Of Loan Origination Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset, accretion of loan origination fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OpenTaxYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax year subject to examination</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OpenTaxYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Open Tax Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedAdministrativeServiceExpensePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued administrative service expense payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedAdministrativeServiceExpensePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Administrative Service Expense Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedAdministrativeServiceExpensePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued administrative service expense payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfChangeInAccountingEstimateTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Estimate [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointSevenFivePercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">January 2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointSevenFivePercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">4.75% Notes due 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointSevenFivePercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Four Point Seven Five Percent Notes Due Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointSevenFivePercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Four Point Seven Five Percent Notes Due Two Thousand Twenty Six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value, assets, transfers into level 3, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExaminationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax examination, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExaminationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Examination, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfStockByClassTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock, Class of Stock [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BorrowingsUnderCreditFacilityNetOfDeferredFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Borrowings under credit facility, net of deferred financing costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BorrowingsUnderCreditFacilityNetOfDeferredFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Borrowings under Credit Facility, Net of Deferred Financing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BorrowingsUnderCreditFacilityNetOfDeferredFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Borrowings under Credit Facility, net of deferred financing costs (Note 6)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tedia Company, LLC - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tedia Company, LLC - Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tedia Company, LLC - revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointNineEightEightPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point nine eight eight percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointNineEightEightPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Nine Eight Eight Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointNineEightEightPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.988% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lender Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIdentifierAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Identifier [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeDividend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeDividend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_EquityMethodInvesteeNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SmallBusinessAdministrationDebenturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SBA Debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SmallBusinessAdministrationDebenturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Small Business Administration Debentures [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SmallBusinessAdministrationDebenturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Small Business Administration debentures.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares repurchased under repurchase program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchased During Period, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Dividend payable date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investments, at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Fair Value, beginning balance</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AutoCrmLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Auto Crm Llc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AutoCrmLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Auto CRM LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AutoCrmLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Auto CRM LLC.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Regular Dividend Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Regular Dividend Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueTreasuryStockReissued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Amount Paid</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetAssetValuePerShareOther_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net asset value per share, other.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_QuantumIRTechnologiesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Quantum IR Technologies, LLC</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_QuantumIRTechnologiesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Quantum ir technologies, llc.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividend one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend One</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net increase in net assets resulting from operations per share - basic and diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Increase Decrease In Net Assets Resulting From Operations To Common Stockholders Basic And Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ADividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ADividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ADividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 A Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRepaymentsOfLinesOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Repayments of) Lines of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRepaymentsOfLinesOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds received from (repayments of) borrowings under Credit Facility, net</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfEquityInvestmentsHeldInPortfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of equity investments held in portfolio companies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Warrants</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalFourthDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Supplemental Fourth Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalFourthDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Supplemental Fourth Dividends</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UsGreenfiberLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">US GreenFiber LLC.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Regular Dividend One</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q3 Supplemental Second Dividends</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HaematologicTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Haematologic Technologies, Inc.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Supplemental Third Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a supplemental third dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Supplemental Third Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt obligations fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Investments, Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Fair Value Disclosure, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfDeferredFinancingCostsAmortizedIntoInterestAndFinancingExpensesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Deferred Financing Costs Amortized into Interest and Financing Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfDeferredFinancingCostsAmortizedIntoInterestAndFinancingExpensesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Deferred Financing Costs Amortized Into Interest And Financing Expenses [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfDeferredFinancingCostsAmortizedIntoInterestAndFinancingExpensesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of deferred financing costs amortized into interest and financing expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Portfolio Composition by Type And by Geographic Region at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL B) One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL B) One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL B)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputVolatilityOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Volatility Of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputVolatilityOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Measurement input, Volatility of credit.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputVolatilityOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Volatility of credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNonQualifyingAssetsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of non-qualifying assets fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNonQualifyingAssetsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Non-qualifying Assets Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNonQualifyingAssetsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of non-qualifying assets fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcDelayedDrawTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tedia Company, LLC - Delayed Draw Term Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcDelayedDrawTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tedia Company, LLC - Delayed Draw Term Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcDelayedDrawTermLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tedia Company, LLC - delayed draw term loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PortionAtFairValueFairValueDisclosureMember_lbl" xlink:role="http://fasb.org/us-gaap/role/label/axisDefault">Portion at Fair Value Measurement [Member] [Default]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PortionAtFairValueFairValueDisclosureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Portion at Fair Value Measurement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PayEntry Financial Services, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PayEntry Financial Services, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayEntry Financial Services, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInvestmentsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Investments [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyPortfolioTurnover_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Portfolio Turnover</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyPortfolioTurnover_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Portfolio turnover ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointSevenNineThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2.793% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointSevenNineThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Point Seven Nine Three Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointSevenNineThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two point seven nine three percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfVotingSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of voting securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfVotingSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Voting Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfVotingSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of voting securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Special Third Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Special Third Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Special Third Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueOfLoansIncludedInInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of loans included in investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueOfLoansIncludedInInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value of Loans included in Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueOfLoansIncludedInInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of loans included in investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Supplemental Second Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Supplemental Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Supplemental Second Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit facility maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Expiration Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 Supplemental Dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Supplemental Dividend [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">O2024 Q3 Supplemental Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Record Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date of Record</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Dividend record date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ApplegateGreenfiberIntermediateIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Applegate Greenfiber Intermediate Inc. (fka US GreenFiber, LLC)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ApplegateGreenfiberIntermediateIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Applegate Greenfiber Intermediate Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ApplegateGreenfiberIntermediateIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Applegate greenfiber intermediate Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnepathSystemsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">OnePath Systems, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnepathSystemsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OnePath Systems, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnepathSystemsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">OnePath Systems, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PartialLoanAndEquitySalesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Partial Loan and Equity Sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PartialLoanAndEquitySalesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Partial Loan And Equity Sales Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PartialLoanAndEquitySalesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Partial loan and equity sales policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DealerbuiltAcquisitionLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">DealerBuilt acquisition, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DealerbuiltAcquisitionLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">DealerBuilt Acquisition, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DealerbuiltAcquisitionLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">DealerBuilt Acquisition, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfBoardRepresentation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of board representation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfBoardRepresentation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Board Representation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfBoardRepresentation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of board representation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income per share-basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Issuance Costs, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.861% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Eight Six One Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point eight six one percent interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAndMoneyMarketFundsOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments and money market funds owned at cost.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAndMoneyMarketFundsOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments and Money Market Funds Owned at Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAndMoneyMarketFundsOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point zero eight two percent interest rate three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Zero Eight Two Percent Interest Rate Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.082% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ElementsBrandsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Elements Brands, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ElementsBrandsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Elements Brands, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ElementsBrandsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Elements Brands, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expenses:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedCapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued capital gains incentive fee payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedCapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Capital Gains Incentive Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedCapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued capital gains incentive fee payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ChoiceTechnologySolutionsLlcDbaChoiceMerchantSolutionsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Choice Technology Solutions, LLC (dba Choice Merchant Solutions, LLC) - Revolving Loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ChoiceTechnologySolutionsLlcDbaChoiceMerchantSolutionsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Choice Technology Solutions, LLC (dba Choice Merchant Solutions, LLC) - Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ChoiceTechnologySolutionsLlcDbaChoiceMerchantSolutionsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Choice Technology Solutions, LLC (dba Choice Merchant Solutions, LLC) - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LevelEducationGroupLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level Education Group LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LevelEducationGroupLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Level Education Group, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LevelEducationGroupLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Level education group, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Supplemental Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a supplemental dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-incentive fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioIncludingIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense Ratio, after Fee Waiver and Incentive Fee Deduction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Debt and Equity Securities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unused commitments amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unused Borrowing Capacity, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q3 Regular First Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q3 Regular First Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q3 Regular First Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien Debt One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Debt One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien debt one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized and unrealized gains (losses) on investments:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, before Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Retained Earnings (Accumulated Deficit), Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Retained Earnings (Accumulated Deficit), Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorSecuredRevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility Borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorSecuredRevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Senior Secured Revolving Credit Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorSecuredRevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Senior secured revolving credit facility.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubordinatedDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subordinated Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubordinatedDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subordinated Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CumulativeUnderwritingFeesAndCommissionAndOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative underwriting fees and commission and offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CumulativeUnderwritingFeesAndCommissionAndOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Underwriting Fees and Commission and Offering Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CumulativeUnderwritingFeesAndCommissionAndOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cumulative underwriting fees and commission and offering costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleMaturityWithinOneYearWeightedAverageYield_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Weighted Average Yield, Maturity, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleMaturityWithinOneYearWeightedAverageYield_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average yield investment percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PinnergyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pinnergy, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PinnergyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pinnergy Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PinnergyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pinnergy, Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MayeshWholesaleFloristLLCFirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mayesh Wholesale Florist, LLC First Lien Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MayeshWholesaleFloristLLCFirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mayesh Wholesale Florist, LLC First Lien Debt.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MayeshWholesaleFloristLLCFirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mayesh Wholesale Florist, LLC - First Lien Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FidusEquityFundILimitedPartnershipMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fidus Equity Fund I, L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FidusEquityFundILimitedPartnershipMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fidus Equity Fund I, Limited Partnership [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FidusEquityFundILimitedPartnershipMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fidus Equity Fund I, L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Regular First Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Regular First Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Regular First Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedInterestAndFeesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued interest and fees payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedInterestAndFeesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Interest And Fees Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccruedInterestAndFeesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued interest and fees payable.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Supplemental Dividend One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Supplemental Dividend One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Supplemental Dividend One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net cash provided by (used for) operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by (used for) operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CustomerExpressionsCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Customer Expressions Corp. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CustomerExpressionsCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Customer expressions corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CustomerExpressionsCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Customer Expressions Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestAndDividendIncomePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and dividend income paid-in-kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestAndDividendIncomePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest and dividend income paid-in-kind.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestAndDividendIncomePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and dividend income paid-in-kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Classification</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point zero eight two percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Zero Eight Two Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.082% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Operating Activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value, Recurring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TotalDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Distribution</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TotalDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total distribution.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseAdministrationFeePayableAndOtherDueToFromAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease administration fee payable and other due to from affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseAdministrationFeePayableAndOtherDueToFromAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease Administration Fee Payable and Other Due To From Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseAdministrationFeePayableAndOtherDueToFromAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administration fee payable and other - due to (from) affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Supplemental Third Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Supplemental Three Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Supplemental Third Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tedia Company LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tedia Company, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TediaCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tedia Company, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfInvestmentPorfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Investment Porfolio Companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfInvestmentPorfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of investment porfolio companies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfInvestmentPorfolioCompanies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of investment portfolio companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt obligations fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RetailSectorsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retail</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RetailSectorsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retail Sectors [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RetailSectorsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Retail sectors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ServicePowerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Service Power Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ServicePowerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Service Power Inc [Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ServicePowerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Service Power Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PolicyholdersDividendPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends to Stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PolicyholdersDividendPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Policyholders' Dividend [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentForIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentForIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment for Incentive Fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetbaseSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Netbase Solutions Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetbaseSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Netbase Solutions, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetbaseSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Netbase solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Investments, Equity Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities, FV-NI</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Equity Securities, FV-NI, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Approach and Technique [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SuitedConnectorLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Suited Connector LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SuitedConnectorLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Suited Connector LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SuitedConnectorLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Suited Connector LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point zero eight two percent interest rate four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Zero Eight Two Percent Interest Rate Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.082% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedGainsOrLossesAndUnrealizedAppreciationOrDepreciationOnInvestmentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Gains or Losses and Unrealized Appreciation or Depreciation on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedGainsOrLossesAndUnrealizedAppreciationOrDepreciationOnInvestmentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gains Or Losses And Unrealized Appreciation Or Depreciation On Investments Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedGainsOrLossesAndUnrealizedAppreciationOrDepreciationOnInvestmentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized gains or losses and unrealized appreciation or depreciation on investments policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfCapitalGainsIncentiveFeeAccrued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of capital gains incentive fee accrued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfCapitalGainsIncentiveFeeAccrued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Capital Gains Incentive Fee Accrued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfCapitalGainsIncentiveFeeAccrued_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of capital gains incentive fee accrued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfPublicOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of public offering price.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfPublicOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of public offering price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfPublicOfferingPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Public Offering Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit facility amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Credit Facility commitment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AffiliateInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Affiliate Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AffiliateInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Affiliate Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AffiliateInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Affiliate investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EstexManufacturingCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Estex manufacturing company llc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EstexManufacturingCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estex Manufacturing Company LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EstexManufacturingCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estex Manufacturing Company LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CashDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Distribution</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CashDistribution_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash distribution.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WonderwareHoldingsLlcDbaCoreBusinessTechnologiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wonderware Holdings, LLC dba CORE Business Technologies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WonderwareHoldingsLlcDbaCoreBusinessTechnologiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wonderware Holdings, LLC dba CORE Business Technologies [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WonderwareHoldingsLlcDbaCoreBusinessTechnologiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wonderware Holdings, LLC (dba CORE Business Technologies).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_January2026NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">January 2026 Notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_January2026NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">January 2026 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_January2026NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">January 2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AerospaceAndDefenseManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aerospace And Defense Manufacturing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AerospaceAndDefenseManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aerospace and Defense Manufacturing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AerospaceAndDefenseManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aerospace and defense manufacturing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentsOfDividendsIncludingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments of dividends including expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentsOfDividendsIncludingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments Of Dividends Including Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentsOfDividendsIncludingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends paid to stockholders, including expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentsOfDividendsIncludingExpenses_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends paid to stockholders, including expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointOneNineZeroPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">3.190% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointOneNineZeroPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Three Point One Nine Zero Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointOneNineZeroPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Three point one nine zero percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notes, net of deferred financing costs (Note 6)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notes Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Notes Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SOFR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.341% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Three Four One Percent Interest Rate Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point three four one percent interest rate two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeeAccruedReversed_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital gains incentive fee accrued (reversed).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeeAccruedReversed_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Gains Incentive Fee Accrued (Reversed)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeeAccruedReversed_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital gains incentive Fee Accrued (Reversed)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q3 Regular Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q3 Regular Dividends [Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Regular Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Regular Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Issued and Outstanding SBA Debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q3 Supplemental Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q3 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Supplemental Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Supplemental Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AomIntermediateHoldcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aom Intermediate Holdco Llc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AomIntermediateHoldcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AOM Intermediate Holdco, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AomIntermediateHoldcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">AOM Intermediate Holdco, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoKDirectIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Two K Direct Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoKDirectIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two K Direct Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoKDirectIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2KDirect, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRateFloor_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Index Floor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRateFloor_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Interest Rate, Floor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HallmarkHealthCareSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hallmark Health Care Solutions Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HallmarkHealthCareSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hallmark Health Care Solutions, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HallmarkHealthCareSolutionsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hallmark Health Care Solutions, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net gain (loss) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrativeServiceExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administrative service expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrativeServiceExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Administrative Service Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrativeServiceExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Administrative service expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiaryOrEquityMethodInvesteeCumulativeNumberOfSharesIssuedForAllTransactions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiaryOrEquityMethodInvesteeCumulativeNumberOfSharesIssuedForAllTransactions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsidiary or Equity Method Investee, Cumulative Number of Shares Issued for All Transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PreIncentiveFeeFixedHurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-incentive fee fixed hurdle rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PreIncentiveFeeFixedHurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-incentive Fee Fixed Hurdle Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PreIncentiveFeeFixedHurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-incentive fee fixed hurdle rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SbicDebentureProgramMaximumAmountOutstandingSbaDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SBIC debenture program, maximum amount outstanding SBA debentures.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SbicDebentureProgramMaximumAmountOutstandingSbaDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/label">SBIC Debenture Program, Maximum Amount Outstanding SBA Debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SbicDebentureProgramMaximumAmountOutstandingSbaDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SBIC debenture program, maximum amount outstanding SBA debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.341% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Three Four One Percent Interest Rate Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point three four one percent interest rate three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MedsurantHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Medsurant Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MedsurantHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Medsurant Holdings LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MedsurantHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Medsurant holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net increase (decrease) in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net increase (decrease) in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AeronixIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aeronix Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AeronixIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aeronix Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AeronixIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aeronix Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmortizationOfDeferredEquityFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of deferred equity financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmortizationOfDeferredEquityFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization Of Deferred Equity Financing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmortizationOfDeferredEquityFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amortization of deferred equity financing costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q3 Supplemental First Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q3 Supplemental First Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Supplemental First Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MaximumAggregateOfferingPriceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum aggregate offering price of common stock under at-the-market program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MaximumAggregateOfferingPriceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Aggregate Offering Price of Common Stock Under At The Market Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MaximumAggregateOfferingPriceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum aggregate offering price of common stock under at-the-market program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net asset value per common share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Net asset value at beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Net asset value at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2025 Q1 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2025 Q1 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2025 Q1 dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of net capital gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Net Capital Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of net capital gains.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Industry Sector [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DelayedDrawCommitmentFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw Commitment Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DelayedDrawCommitmentFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw Commitment Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DelayedDrawCommitmentFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw commitment four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Purchases of debt and equity investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchases of debt and equity investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BpThriftBuyerLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BP Thrift Buyer, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BpThriftBuyerLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BP Thrift Buyer, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BpThriftBuyerLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BP Thrift Buyer, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantsNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantsNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantsNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrants notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total dividend income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total dividend income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FeeIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fee Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FeeIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fee Income Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FeeIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fee income policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivableFromStockOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds receivable from stock offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivableFromStockOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds Receivable From Stock Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivableFromStockOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds receivable from stock offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CumulativeGrossProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative gross proceeds from issuance of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CumulativeGrossProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Gross Proceeds from Issuance of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CumulativeGrossProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cumulative gross proceeds from issuance of common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_JumoHealthIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Jumo Health, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_JumoHealthIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Jumo Health, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_JumoHealthIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Jumo Health, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average debt per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Average Debt Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Average debt per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Investments, Percent of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value percentage of net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income, Operating, Paid in Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total payment-in-kind interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperatingPaidInKind_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Total payment-in-kind interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesWestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States West</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesWestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">United States West [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesWestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">United States West.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net Change in Unrealized Appreciation (Depreciation)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total net change in unrealized appreciation (depreciation) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net change in unrealized appreciation (depreciation) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net change in unrealized (appreciation) depreciation on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Change In Unrealized (appreciation) Depreciation on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net change in unrealized (appreciation) depreciation on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HealthcareProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Healthcare Products</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HealthcareProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Healthcare Products [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HealthcareProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Healthcare products.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WeightedAveragePriceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted-average price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WeightedAveragePriceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Price of Common Stock Under At The Market Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WeightedAveragePriceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted average price of common stock under at the market program.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecuredBorrowingsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Secured Borrowings</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ControlInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Control Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ControlInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Control Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ControlInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Control investments.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Supplemental Dividends [Member]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossInvestmentIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gross investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossInvestmentIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gross Investment Income [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossInvestmentIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Income:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Credit Facility upfront fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred upfront fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recent Accounting Pronouncement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OriginationAndClosingFee_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Origination and Closing Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OriginationAndClosingFee_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Origination And closing Fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OriginationAndClosingFee_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Origination and closing fee.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q3DividendsTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q3 Dividends Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q3DividendsTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q3 Dividends Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q3DividendsTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2025 Q3 Dividends Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UpgCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">UPG Company, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UpgCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">UPG Company, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UpgCompanyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">UPG Company, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_CA_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Canada</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_CA_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CANADA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentAndMoneyMarketFundsOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percent of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentAndMoneyMarketFundsOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment and money market funds owned percent of net assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentAndMoneyMarketFundsOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment and Money Market Funds Owned Percent of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scheduled to Mature Debt Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Maturities of Long-Term Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental dividend two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Dividend Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Dividend Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentMaturityPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment maturity period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentMaturityPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Maturity Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentMaturityPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment maturity period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Aggregate principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total outstanding SBA debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issued additional debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ConsumerServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consumer Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ConsumerServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Consumer Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ConsumerServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consumer Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourThreeNinePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.439% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourThreeNinePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Four Three Nine Percent Interest Rate Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourThreeNinePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point four three nine percent interest rate two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Capital gains incentive fee payable - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital gains incentive fee payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Gains Incentive Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital gains incentive fee payable.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Market value at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredChargesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred Offering Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredChargesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Charges, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputWeightedAverageCostOfCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Cost of Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputWeightedAverageCostOfCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Weighted Average Cost of Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputWeightedAverageCostOfCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Measurement input, weighted average cost of capital.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SixPointZeroFourSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">6.047% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SixPointZeroFourSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Six Point Zero Four Seven Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SixPointZeroFourSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Six point zero four seven percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestAndDividendIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and Dividend Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestAndDividendIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest And Dividend Income Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestAndDividendIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest and dividend income policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomePaymentInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment-in-kind Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomePaymentInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income Payment In Kind Interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomePaymentInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment income payment in kind interest income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomePaymentInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payment-in-kind Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized appreciation (depreciation) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageFullyDilutedEquityOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Average fully diluted equity ownership Percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageFullyDilutedEquityOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Average Fully Diluted Equity Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageFullyDilutedEquityOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average fully diluted equity ownership percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AffiliateInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Affiliate Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AffiliateInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Affiliate Investment Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AffiliateInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Affiliate investment member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Money market funds owned percent of net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds Owned Percent of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmIndividualTitleAndPositionOrGroupOrCommitteeNameExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmIndividualTitleAndPositionOrGroupOrCommitteeNameExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment reporting, codm, individual title and position or group name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Regular First Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Regular First Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a regular first dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital gains incentive fee payable - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Gains Incentive Fee Payable Due to Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CapitalGainsIncentiveFeePayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital gains incentive fee payable due to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maximum amount of shares, sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public offering of common stock, net of expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossInvestmentIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gross Investment Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossInvestmentIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q2DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 Q2 Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q2DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 Q2 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q2DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 Q2 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ADividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ADividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ADividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds Interest Rate Paid In Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Money market funds interest rate paid in kind.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment interest rate, PIK</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebentureLeverageFees_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">SBA debenture leverage fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebentureLeverageFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leverage fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebentureLeverageFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debenture Leverage Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebentureLeverageFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debenture leverage fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WinonaFoodsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Winona Foods Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WinonaFoodsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Winona Foods, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WinonaFoodsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Winona Foods, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash payments for taxes, net of tax refunds received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Paid, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Taxes Paid, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_StockRepurchaseProgramPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Repurchase Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_StockRepurchaseProgramPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchase Program Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_StockRepurchaseProgramPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock repurchase program policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDistributionsInExcessOfNetIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Distributable Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDistributionsInExcessOfNetIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Distributions in Excess of Net Income [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, at Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash and Cash Equivalents, at Carrying Value, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash and Cash Equivalents, at Carrying Value, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTaxReturnOfCapitalDistributionPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Taxes paid on deemed distributions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTaxReturnOfCapitalDistributionPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Tax Return of Capital Distribution, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioExcludingIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expenses other than incentive fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioExcludingIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense Ratio, after Fee Waiver and before Incentive Fee Deduction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments of Dividends, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends payable to stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorAssetCoverageRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Senior asset coverage ratio.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorAssetCoverageRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Senior Asset Coverage Ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorAssetCoverageRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Senior asset coverage ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consolidation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of minimum qualifying assets to purchase non qualifying assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Minimum Qualifying Assets To Purchase Non Qualifying Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of minimum qualifying assets to purchase non qualifying assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_W50HoldingsLlcPreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">W50 Holdings, LLC - Preferred Equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_W50HoldingsLlcPreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">W50 Holdings, LLC - Preferred Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_W50HoldingsLlcPreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">W50 Holdings, LLC - Preferred Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EquityInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EquityInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EquityInvestmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EstimateOfFairValueFairValueDisclosureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EstimateOfFairValueFairValueDisclosureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estimate of Fair Value Measurement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q4DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q4 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q4DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q4 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q4DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 q4 dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien debt.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, after Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net investment income before income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesIndustryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Industry Sector [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 Supplemental Dividend One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Supplemental Dividend One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Supplemental Dividend One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInIncomeIncentiveFeePayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income incentive fee payable - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInIncomeIncentiveFeePayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease in Income Incentive Fee Payable Due To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInIncomeIncentiveFeePayableDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in income incentive fee payable due to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental dividend one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Dividend One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SupplementalDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Dividend One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds, at Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfOriginalIssueDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accretion of original issue discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfOriginalIssueDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset, Accretion Of Original Issue Discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfOriginalIssueDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset, Accretion Of Original Issue Discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdministrativeFeesExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administrative service expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdministrativeFeesExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Administrative Fees Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockDividendsPerShareDeclared_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockDividendsPerShareDeclared_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Dividends, Per Share, Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpenseRatioToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpenseRatioToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpenseRatioToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Expense Ratio To Average Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpenseRatioToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company, expense ratio to average net assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Secured Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Secured borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Affiliation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentVariableIndexFloorRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Index Floor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentVariableIndexFloorRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Variable Index Floor Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentVariableIndexFloorRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment variable index floor rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchasedDuringPeriodValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchased During Period, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputAssetCoverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Coverage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputAssetCoverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Asset Coverage [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MeasurementInputAssetCoverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Measurement input, asset coverage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdditionalInterestRateOnInvestmentsPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional interest rate on investments, PIK</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdditionalInterestRateOnInvestmentsPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Interest Rate On Investments Paid In Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdditionalInterestRateOnInvestmentsPaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Additional interest rate on investments paid-in kind.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q1 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024Q1 Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024Q1 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excise tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excise Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excise tax.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate payment term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Frequency of Periodic Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Preferred Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Preferred Equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by (used for) financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net cash provided by (used for) financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Regular Second Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Regular Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a regular second dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Secured borrowings.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Secured borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfCommonStockTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Summary of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfCommonStockTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Common Stock [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfCommonStockTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity Note [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable and other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Payable and Other Operating Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CarryingReportedAmountFairValueDisclosureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CarryingReportedAmountFairValueDisclosureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CarryingReportedAmountFairValueDisclosureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reported Value Measurement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Special Dividend Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Special Dividend Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Special Dividend Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmProfitLossMeasureHowUsedDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingCodmProfitLossMeasureHowUsedDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment reporting, codm, profit (loss) measure, how used, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ScheduleOfInterestAndFinancingExpensesRelatedToDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Interest and Fees Related to Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ScheduleOfInterestAndFinancingExpensesRelatedToDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Interest And Financing Expenses Related To Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ScheduleOfInterestAndFinancingExpensesRelatedToDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of interest and financing expenses related to debt.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base management fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax provision (benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_Percentageoffairvalue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_Percentageoffairvalue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PercentageOfFairValue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_Percentageoffairvalue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q3DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 Q3 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q3DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 Q3 Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q3DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 Q3 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterestRatePercentageBasedOnAfterCertainConditionsSatisfied_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument interest rate percentage based on after certain conditions satisfied.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterestRatePercentageBasedOnAfterCertainConditionsSatisfied_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Interest Rate Percentage Based on After Certain Conditions Satisfied</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterestRatePercentageBasedOnAfterCertainConditionsSatisfied_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate after certain conditions satisfied</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EighteenAndTwentyOnePortfolioCompanyInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">18 and 21 Portfolio Company Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EighteenAndTwentyOnePortfolioCompanyInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Eighteen and Twenty One Portfolio Company Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EighteenAndTwentyOnePortfolioCompanyInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Eighteen and twenty one portfolio company investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net assets at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SummaryOfInvestmentHoldingsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Investment Holdings [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentPoolingDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pooling Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentPoolingDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Pooling Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentPoolingDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, pooling date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointFiveThreeThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Four point five three three percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointFiveThreeThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Four Point Five Three Three Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FourPointFiveThreeThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">4.533% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInvestmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Investments [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InfoTechOperatingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Info Tech Operating, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InfoTechOperatingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Info Tech Operating, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InfoTechOperatingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Info Tech Operating, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpecialtyDistributionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Specialty Distribution</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpecialtyDistributionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Specialty Distribution [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpecialtyDistributionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Specialty distribution.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.861% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Eight Six One Percent Interest Rate One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point eight six one percent interest rate one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Regular Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Regular Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a regular dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Control Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Affiliated Issuer, Controlled [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssetMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity investments, Warrants range</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssetMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset, Measurement Input</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentMaturityYearRangeEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, maturity year range, end</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentMaturityYearRangeEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Maturity Year Range, End</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentMaturityYearRangeEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument, maturity year range, end.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gain (loss) on investments, net of tax (provision)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Gain (Loss) on Investment, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxesPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Taxes payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxesPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Taxes Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxesPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Taxes Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_VirtexEnterprisesLpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Virtex Enterprises, LP.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_VirtexEnterprisesLpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Virtex Enterprises, LP [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_VirtexEnterprisesLpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Virtex Enterprises, LP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LaboratoryTestingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Laboratory Testing, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LaboratoryTestingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Laboratory Testing, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LaboratoryTestingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Laboratory Testing, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_StewardHoldingLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Steward Holding LLC (dba Steward Advanced Materials)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_StewardHoldingLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Steward Holding LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_StewardHoldingLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Steward holding LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Shares Purchased and Reissued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">DRIP Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares issued under dividend reinvestment plan, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourthreeNinePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.439% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourthreeNinePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point FourThree Nine Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourthreeNinePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point four three nine percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtWeightedAverageInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted average stated interest rate, period end</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtWeightedAverageInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Weighted average stated interest rate, period end</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtWeightedAverageInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtWeightedAverageInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt, Weighted Average Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Percent of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total net assets percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Net Assets, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputDiscountRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Discount Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputDiscountRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentMaturityYearRangeStart1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, maturity year range, start</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentMaturityYearRangeStart1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Maturity Year Range Start 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentMaturityYearRangeStart1_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument maturity year range start 1.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WrittenNoticePeriodForTerminationOfAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Written notice period for termination of agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WrittenNoticePeriodForTerminationOfAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Written notice period for termination of agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityMinimumUtilizationCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Performing first lien bank loans, minimum percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityMinimumUtilizationCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum utilization of commitment fee percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityMinimumUtilizationCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Minimum Utilization Commitment Fee Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LineOfCreditFacilityMinimumUtilizationCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, minimum utilization commitment fee percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Use of Estimates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Use of Estimates, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred Financing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Financing Costs Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred financing costs policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and Cash Equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ValuationTechniqueOptionPricingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique, Option Pricing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ValuationTechniqueOptionPricingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Valuation technique option pricing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ValuationTechniqueOptionPricingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Option Pricing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Regular Third Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a regular third dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ARegularThirdDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Regular Third Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Dividends to stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amount Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Amount Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementInputsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Inputs Used to Value Debt Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementInputsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentRedemptionDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, redemption description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentRedemptionDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Redemption, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentRiskPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Risks</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentRiskPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Risk Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentRiskPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment risk policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtIssueCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Notes debt issue costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtIssueCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt issue costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtIssueCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Issue Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtIssueCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt issue costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FidusInvestmentAdvisorsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fidus Investment Advisors LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FidusInvestmentAdvisorsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fidus Investment Advisors LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FidusInvestmentAdvisorsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fidus Investment Advisors LLC .</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpectraAAndDAcquisitionIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Spectra A&amp;D Acquisition, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpectraAAndDAcquisitionIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Steward Holding LLC (dba Steward Advanced Materials)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpectraAAndDAcquisitionIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Spectra A&amp;D Acquisition, Inc. (fka FDS Avionics Corp.)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpectraAAndDAcquisitionIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Spectra A&amp;D Acquisition, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCommonStock_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividends, Common Stock, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total expenses before base management fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivedFromRepaymentsOfSecuredBorrowingsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds received from repayments of secured borrowings, net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivedFromRepaymentsOfSecuredBorrowingsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds Received From Repayments Of Secured Borrowings, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsReceivedFromRepaymentsOfSecuredBorrowingsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds received from (repayments of) Secured Borrowings, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FarResearchIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">FAR Research Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FarResearchIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">FAR Research Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FarResearchIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">FAR research Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Regular Dividend Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Regular Dividend Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Regular Dividend Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and financing expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total interest and financing expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and Debt Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ShareValueAvailableUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Available under ATM program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ShareValueAvailableUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Value Available Under At The Market Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ShareValueAvailableUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share value available under at the market program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecondLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second Lien Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecondLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SecondLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second lien debt.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantOrRightsPercentageOfOutstandingDebtPrincipalToPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrant or rights percentage of outstanding debt principal to purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantOrRightsPercentageOfOutstandingDebtPrincipalToPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant Or Rights Percentage Of Outstanding Debt Principal To Purchase</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantOrRightsPercentageOfOutstandingDebtPrincipalToPurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant or rights percentage of outstanding debt principal to purchase.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Measurements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.861% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Eight Six One Percent Interest Rate Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point eight six one percent interest rate three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First Lien Debt Six</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Debt Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FirstLienDebtSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First lien debt six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Events</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net assets at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Net Assets, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Net Assets, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Special Dividend Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Special Dividend Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Special Dividend Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EnvironmentalIndustriesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Environmental Industries</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EnvironmentalIndustriesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Environmental Industries [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_EnvironmentalIndustriesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Environmental industries.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Loss on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Realized losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Realized losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Loss on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyDistributionsFromCapitalGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Distributions from capital gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyDistributionsFromCapitalGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Distributions From Capital Gains Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyDistributionsFromCapitalGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company, distributions from capital gains per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PrimeAeGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prime AE Group, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PrimeAeGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prime AE Group, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PrimeAeGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prime AE Group, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental information and non-cash activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Portfolio Company Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income per share-diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DetechtionHoldingsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Detechtion Holdings, LLC - Revolving Loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DetechtionHoldingsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Detechtion Holdings, LLC - Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DetechtionHoldingsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Detechtion Holdings, LLC - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAsPercentageOfAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments as percentage of total assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAsPercentageOfAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments As Percentage Of Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAsPercentageOfAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments as percentage of assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Distribution</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividends, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentOfFinancingAndStockIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payment of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentOfFinancingAndStockIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment of Financing and Stock Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentOfFinancingAndStockIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payment of Financing and Stock Issuance Costs, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitrancheInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unitranche Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitrancheInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unitranche investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1RegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2025 Q1 Regular Second Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1RegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q1 Regular Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q1RegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q1 regular second dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AldingerCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aldinger company.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AldingerCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aldinger Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AldingerCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aldinger Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MirageTrailersLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mirage Trailers LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MirageTrailersLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mirage Trailers LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MirageTrailersLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mirage trailers LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ValuationTechniqueEnterpriseValueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Valuation technique, enterprise value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ValuationTechniqueEnterpriseValueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Enterprise Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ValuationTechniqueEnterpriseValueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique, Enterprise Value [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Forecast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Forecast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Number of Shares Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Public offering of common stock, net of expenses, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total net realized gain (loss) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net realized gain (loss) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gain (loss) on investments, net of taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gain) loss on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized gain (loss) on investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Affiliation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Gross Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesMidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States Midwest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesMidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">United States Midwest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesMidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">United States Midwest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommitmentsOutstandingToFundVariousUndrawnRevolvingLoansOtherDebtInvestmentsAndCapitalCommitments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Unfunded Commitment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommitmentsOutstandingToFundVariousUndrawnRevolvingLoansOtherDebtInvestmentsAndCapitalCommitments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments outstanding to fund various undrawn revolving loans, other debt investments and capital commitments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommitmentsOutstandingToFundVariousUndrawnRevolvingLoansOtherDebtInvestmentsAndCapitalCommitments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments Outstanding to Fund Various undrawn revolving loans, other debt investments and capital commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommitmentsOutstandingToFundVariousUndrawnRevolvingLoansOtherDebtInvestmentsAndCapitalCommitments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commitments outstanding to fund various undrawn revolving loans, other debt investments and capital commitments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentVariableInterestRateTypeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Variable Interest Rate, Type [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForPurchaseOfSecuritiesOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchase of investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForPurchaseOfSecuritiesOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Purchase of Securities, Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Supplemental First Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Supplemental First Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalFirstDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a supplemental first dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income incentive fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Incentive Fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFee_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Income incentive fee</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OwnershipPercentageOfOutstandingVotingSecuritiesInPortfolioInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ownership percentage of outstanding voting securities in portfolio investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OwnershipPercentageOfOutstandingVotingSecuritiesInPortfolioInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ownership Percentage of Outstanding Voting Securities in Portfolio Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OwnershipPercentageOfOutstandingVotingSecuritiesInPortfolioInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ownership percentage of outstanding voting securities in portfolio investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HilcoPlasticsHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hilco Plastics Holdings, LLC (dba Hilco Technologies)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HilcoPlasticsHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hilco Plastics Holdings LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_HilcoPlasticsHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hilco plastics holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Organization and Nature of Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfPortfolioInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of portfolio investments at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfPortfolioInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Portfolio Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfPortfolioInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of portfolio investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInCapitalGainsIncentiveFeeReversalDueToFromAffiliate_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Capital gains incentive fee (reversal) - due to (from) affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInCapitalGainsIncentiveFeeReversalDueToFromAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Capital Gains Incentive Fee Reversal Due To From Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInCapitalGainsIncentiveFeeReversalDueToFromAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in capital gains incentive fee reversal due to from affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRatePaidInCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Interest Rate, Paid in Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrationFeesPayableAndOtherDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administration fee payable and other - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrationFeesPayableAndOtherDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Administration Fees Payable and Other Due To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrationFeesPayableAndOtherDueToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Administration fees payable and other due to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PugetCollisionLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Puget Collision Llc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PugetCollisionLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Puget Collision, L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PugetCollisionLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Puget Collision, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointTwoZeroNinePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">3.209% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointTwoZeroNinePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Three Point Two Zero Nine Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointTwoZeroNinePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Three point two zero nine percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Parties [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Average Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Average net assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFeeAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">SBA debenture commitment fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFeeAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitment fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFeeAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Fee Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNetCapitalGainsRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of net capital gains realized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNetCapitalGainsRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Net Capital Gains Realized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfNetCapitalGainsRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of net capital gains realized.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_March2030NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">March 2030 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_March2030NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">March 2030 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_March2030NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">March 2030 notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Advisory Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Advisory Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment advisory agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WesternsSmokehouseLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Westerns Smokehouse, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WesternsSmokehouseLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Westerns Smokehouse LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WesternsSmokehouseLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Western's Smokehouse, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetRealizedGainLossOnInvestmentsNetOfTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net realized gain (loss) on investments, net of taxes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetRealizedGainLossOnInvestmentsNetOfTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Realized Gain (Loss) on Investments, Net of Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetRealizedGainLossOnInvestmentsNetOfTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gain (loss) on investments, net of taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CardboardBoxLlcDbaAnthonysCoalFiredPizzaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cardboard Box Llc Dba Anthonys Coal Fired Pizza</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CardboardBoxLlcDbaAnthonysCoalFiredPizzaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cardboard Box LLC dba Anthony's Coal Fired Pizza [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CardboardBoxLlcDbaAnthonysCoalFiredPizzaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cardboard Box LLC dba Anthony's Coal Fired Pizza.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Highlights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of reportable segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Reportable Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q2 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q2 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Quaterly Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL A) One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL A) One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL A)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Type [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Money Market Funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average number of shares outstanding - basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ExpensesNetOfBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total expenses, net of base management fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ExpensesNetOfBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Expenses Net of Base Management Fee Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ExpensesNetOfBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Expenses net of base management fee waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Money market funds at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds At Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point zero eight two percent interest rate one</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Zero Eight Two Percent Interest Rate One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.082% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PfanstiehlIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pfanstiehl, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PfanstiehlIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pfanstiehl Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PfanstiehlIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pfanstiehl, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyPortfolioTurnoverRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Portfolio turnover ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyPortfolioTurnoverRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Portfolio Turnover Ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyPortfolioTurnoverRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company, portfolio turnover ratio.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3DividendsOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 Dividends One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3DividendsOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Dividends One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3DividendsOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q3 Dividends One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net proceeds from common stock under ATM program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetProceedsFromLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Proceeds from loan origination fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetProceedsFromLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset, Proceeds From Loan Origination Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetProceedsFromLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset, proceeds from loan origination fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnePointThreeNineEightPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">1.398% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnePointThreeNineEightPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">One Point Three Nine Eight Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnePointThreeNineEightPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">One point three nine eight percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividend two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Supplemental Dividend Three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Supplemental Dividend Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Supplemental Dividend Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings and Net Asset Value per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AtTheMarketOfferingProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">At-the-Market Offering Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AtTheMarketOfferingProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At-the-Market Offering Program [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AtTheMarketOfferingProgramMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At-the-market offering program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset, Statement of Financial Position [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL B) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL B).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL B)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL A) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL A).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PayEntry Financial Services, Inc. (dba Payentry) - Second Lien (DDTL A)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InformationTechnologyServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Information Technology Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InformationTechnologyServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Information Technology Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InformationTechnologyServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Information Technology Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PrepaymentOfDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepayment of debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PrepaymentOfDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepayment of Debentures</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PrepaymentOfDebentures_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepayment of debentures.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_November2026NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">November 2026 Notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_November2026NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">November 2026 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_November2026NotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">November 2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretionOfLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accretion of loan origination fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretionOfLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accretion of Loan Origination Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretionOfLoanOriginationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accretion of loan origination fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInPayablesForInvestmentsPurchased_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in payables for investments purchased.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInPayablesForInvestmentsPurchased_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) In Payables For Investments Purchased</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInPayablesForInvestmentsPurchased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payables for investments purchased</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Investments, Equity, Range</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities, FV-NI, Measurement Input</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate fair value of total portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-sale, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Base management fee payable, net of base management fee waiver - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base management fee payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregateAmountOfCapitalGainsIncentiveFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate amount of capital gains incentive fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregateAmountOfCapitalGainsIncentiveFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate amount of capital gains incentive fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregateAmountOfCapitalGainsIncentiveFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate amount of capital gains incentive fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Debt, net of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Debt, net of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Borrowings under Credit Facility, net of deferred financing costs (Note 6)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Borrowings under Credit Facility, net of deferred financing costs (Note 6)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Line of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-term Line of Credit, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">NET ASSETS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInvestmentsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Investments [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WeightedAverageOfferingPriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average offering Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WeightedAverageOfferingPriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Offering Price of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WeightedAverageOfferingPriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Weighted average offering price of common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TransportationServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transportation Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TransportationServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Transportation Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TransportationServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Transportation services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpensesOther_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidExpensesOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expenses, Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BedfordPrecisionPartsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bedford Precision Parts L L C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BedfordPrecisionPartsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bedford Precision Parts L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BedfordPrecisionPartsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bedford precision parts LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Amount Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">DRIP Shares Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares issued under dividend reinvestment plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Regular Dividend One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Regular Dividend One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Regular Dividend One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThrustFlightLlcFirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Thrust Flight LLC - First Lien Debt.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThrustFlightLlcFirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Thrust Flight LLC - First Lien Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThrustFlightLlcFirstLienDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thrust Flight LLC - First Lien Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WorldToursLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">World Tours LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WorldToursLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">World Tours LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WorldToursLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">World Tours LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Regular Second Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Regular Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ARegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Regular Second Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsInterestRatePaidInCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds Interest Rate Paid In Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsInterestRatePaidInCash_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Money market funds interest rate paid in cash.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MoneyMarketFundsInterestRatePaidInCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, Interest Rate, Paid in Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommissionsUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commissions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommissionsUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commissions Under At The Market Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommissionsUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commissions under at the market program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation of Beginning and Ending Balances for Fair Valued Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q4DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 Q4 Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q4DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 Q4 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q4DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 Q4 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FeeIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fee Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FeeIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total fee income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net increase (decrease) in cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net increase (decrease) in cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Per common share data:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwriting discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underwriting Discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underwriting discounts.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stated interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Operating and Nonoperating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointFiveZeroPercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">November 2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointFiveZeroPercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">3.50% Notes Due 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointFiveZeroPercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Three Point Five Zero Percent Notes Due Two Thousand Twenty Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ThreePointFiveZeroPercentNotesDueTwoThousandTwentySixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Three point five zero percent notes due two thousand twenty six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">DRIP Share Issue Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IproTechLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ipro Tech, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IproTechLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ipro Tech, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IproTechLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ipro tech, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Investments, Warrants fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Derivative Asset, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentVariableIndexSpreadRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Index Spread</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentVariableIndexSpreadRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Variable Index Spread Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentVariableIndexSpreadRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment variable index spread rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsExcludingSecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Financing Costs Excluding Secured Borrowings, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsExcludingSecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred financing costs excluding secured borrowings.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsExcludingSecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Financing Costs Excluding Secured Borrowings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredFinancingCostsExcludingSecuredBorrowings_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt, net of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Significant Unobservable Inputs by Valuation Technique to Determine Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Effective Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accrued Interest Receivable, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASSETS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Distribution</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends, Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsCash_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividends, Cash, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CardbackIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cardback Intermediate L L C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CardbackIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cardback Intermediate L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CardbackIntermediateLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cardback intermediate LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Special Dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Special Dividend [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Special Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Acquisition Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Investment acquisition date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Invested in debt and common equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Business services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UtilitiesServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Utilities services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UtilitiesServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Utilities Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UtilitiesServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Utilities: Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnsightIndustriesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Onsight Industries, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnsightIndustriesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Onsight industries, llc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_OnsightIndustriesLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Onsight Industries, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossProceedsFromIssuanceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross proceeds received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossProceedsFromIssuanceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gross Proceeds From Issuance Of Common Stock Under At The Market Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossProceedsFromIssuanceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gross proceeds from issuance of common stock under at the market program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GrossProceedsFromIssuanceOfCommonStockUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Gross Proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Incentive Fee to Average Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fee, net of incentive fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other general and administrative expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_K2MergerAgreementAgentLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">K2 Merger Agreement Agent, LLC (fka K2 Industrial Services, Inc.)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_K2MergerAgreementAgentLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">K2 Merger Agreement Agent LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_K2MergerAgreementAgentLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">K2 merger agreement agent LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedAmortizationDeferredFinanceCosts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: accumulated amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedAmortizationDeferredFinanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: accumulated amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedAmortizationDeferredFinanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Amortization, Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net Increase Decrease in Net Assets Resulting from Operations to Common Stockholders Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Increase Decrease in Net Assets Resulting from Operations to Common Stockholders Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net increase in net assets resulting from operations per share - basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BuildingProductsManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Building Products Manufacturing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BuildingProductsManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Building Products Manufacturing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BuildingProductsManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Building products manufacturing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsFromSalesAndRepaymentsOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from sales and repayments of investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsFromSalesAndRepaymentsOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sales and Repayments of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ProceedsFromSalesAndRepaymentsOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from sales and repayments of investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourThreeNinePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.439% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourThreeNinePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Four Three Nine Percent Interest Rate One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointFourThreeNinePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point four three nine percent interest rate one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfInterestInCorporateUnit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of participating interest principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfInterestInCorporateUnit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale of Interest in Corporate Unit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">End of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfCommonStockAtmProgram1TableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Equity ATM Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfCommonStockAtmProgram1TableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Common Stock ATM Program 1 [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfCommonStockAtmProgram1TableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of common Sstock ATM program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityLenderDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Lender [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Notes underwriting discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwriting discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Underwriting Discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DeferredUnderwritingDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred underwriting discounts.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit facility, interest rate per annum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Unused commitment fee rate, period end</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unused portion of Credit Facility commitment percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GmpHvacLlcDbaMcgeeHeatingAirLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">GMP HVAC, LLC (dba McGee Heating &amp; Air, LLC) - revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GmpHvacLlcDbaMcgeeHeatingAirLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">GMP HVAC, LLC (dba McGee Heating &amp; Air, LLC) - Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GmpHvacLlcDbaMcgeeHeatingAirLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">GMP HVAC, LLC (dba McGee Heating &amp; Air, LLC) - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 Q1 Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 Q1 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023Q1DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 Q1 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Holdings, Schedule of Investments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentHoldingsScheduleOfInvestmentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Investments Type With Corresponding Percentage of Total Portfolio Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnderwritingFeesAndCommissionsUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underwriting fees and commissions under at the market program.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnderwritingFeesAndCommissionsUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underwriting Fees And Commissions Under At The Market Program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnderwritingFeesAndCommissionsUnderAtTheMarketProgram_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwriting Fees and Commissions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Additional Paid in Capital, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Additional Paid in Capital, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Additional Paid in Capital, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ManagementFeesAnnualRatePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees annual rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ManagementFeesAnnualRatePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fees Annual Rate Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ManagementFeesAnnualRatePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Management fees annual rate percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fee - income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesSoutheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States Southeast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesSoutheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">United States Southeast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesSoutheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">United States Southeast.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointThreeSevenSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2.377% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointThreeSevenSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Point Three Seven Seven Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointThreeSevenSevenPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two point three seven seven percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestOnIdleFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest on idle funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestOnIdleFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest on Idle Funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InterestOnIdleFunds_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest on idle funds.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average Price Paid Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Acquired, Average Cost Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueAssetsLevelTwoToLevelOneTransfersAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets Level Two To Level One Transfers Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueAssetsLevelTwoToLevelOneTransfersAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value assets level two to level one transfers amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueAssetsLevelTwoToLevelOneTransfersAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value, assets, level 2 to level 1 transfers, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, by Balance Sheet Grouping [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorSecuredRevolvingCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorSecuredRevolvingCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Senior Secured Revolving Credit Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SeniorSecuredRevolvingCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Senior secured revolving credit agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.861% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Eight Six One Percent Interest Rate Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointEightSixOnePercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point eight six one percent interest rate two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Offering expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: unamortized deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: unamortized deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Unamortized deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointNineEightThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point nine eight three percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointNineEightThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Nine Eight Three Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointNineEightThreePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.983% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Debt Investment on Non-Accrual Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FishbowlSolutionsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fishbowl Solutions Llc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FishbowlSolutionsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fishbowl Solutions, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FishbowlSolutionsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fishbowl Solutions, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfessionalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Professional fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfessionalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Professional Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Regular Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q2 Regular Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2RegularDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q2 Regular Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value, assets, transfers out of level 3, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturn_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on net asset value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturn_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Total Return</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Stated Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentAssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument asset coverage percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentAssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Asset Coverage Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentAssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt Instrument Asset Coverage Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregateAmountOfOutstandingOfSeniorSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate amount of outstanding of senior securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregateAmountOfOutstandingOfSeniorSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Amount of Outstanding of Senior Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregateAmountOfOutstandingOfSeniorSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate amount of outstanding of senior securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmericanAllwasteLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">American AllWaste LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmericanAllwasteLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">American AllWaste LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AmericanAllwasteLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">American AllWaste LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretionOfOriginalIssueDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accretion of original issue discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretionOfOriginalIssueDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accretion of Original Issue Discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AccretionOfOriginalIssueDiscount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accretion of original issue discount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maximum number of common stock purchasable under stock repurchase program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum common stock can be purchased under repurchase program</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Repurchase Program, Authorized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyDividendsToStockholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Dividends To Stockholders Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyDividendsToStockholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company, dividends to stockholders per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyDividendsToStockholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared to stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Approach and Technique [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q2 Supplemental Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q2SupplementalDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Supplemental Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedGainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedGainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gains Losses On Extinguishment Of Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedGainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized gains (losses) on extinguishment of debt.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfUnamortizedDeferredFinancingCostsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Outstanding Debt Net of Unamortized Deferred Financing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfUnamortizedDeferredFinancingCostsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Unamortized Deferred Financing Costs [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SummaryOfUnamortizedDeferredFinancingCostsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of unamortized deferred financing costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net unrealized appreciation (depreciation) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net unrealized appreciation (depreciation) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss) on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Unrealized Gain (Loss) on Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base management fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Base Management Fee Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company, base management fee waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Supplemental Dividend Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Supplemental Dividend Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Supplemental Dividend Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommonEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommonEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommonEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common Equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss) Ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInBaseManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base management fee payable, net of base management fee waiver - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInBaseManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Base Management Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncreaseDecreaseInBaseManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in base management fee payable.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeOneZeroPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Three One Zero Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeOneZeroPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five Point Three One Zero Percent Interest Rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeOneZeroPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">5.310% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net increase (decrease) in net assets resulting from operations to net cash provided by (used for) operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FraserSteelLLCRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fraser Steel LLC - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FraserSteelLLCRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fraser Steel LLC Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FraserSteelLLCRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fraser Steel LLC Revolving Loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeExpenseNetAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeExpenseNetAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income (Expense), Net after tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeExpenseNetAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment Income (Expense), Net after tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeExpenseNetAfterTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeFeeIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fee Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeFeeIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income Fee Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentIncomeFeeIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment income fee income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInvestmentInNumberOfPortfolioCompaniesOnNonAccrualStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt investments in portfolio companies on non-accrual status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInvestmentInNumberOfPortfolioCompaniesOnNonAccrualStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Investment In Number Of Portfolio Companies On Non Accrual Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInvestmentInNumberOfPortfolioCompaniesOnNonAccrualStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt investment in number of portfolio companies on non-accrual status.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 Supplemental Dividend Two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Supplemental Dividend Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3SupplementalDividendTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2024 Q3 Supplemental Dividend Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WarrantsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrants policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueAssetsLevelOneToLevelTwoTransfersAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Assets Level One To Level Two Transfers Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueAssetsLevelOneToLevelTwoTransfersAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value assets level one to level two transfers amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueAssetsLevelOneToLevelTwoTransfersAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value, assets, level 1 to level 2 transfers, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Total Return, Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyTotalReturnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on market value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis of Accounting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointOneSevenTwoPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2.172% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointOneSevenTwoPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Point One Seven Two Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_TwoPointOneSevenTwoPercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two point one seven two percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Index Spread</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Basis Spread, Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MesaLineServicesLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mesa Line Services, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MesaLineServicesLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mesa Line Services LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MesaLineServicesLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mesa line services LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfTaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of taxable income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfTaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Taxable Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PercentageOfTaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of taxable income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Value, Issued, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Value, Issued, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Common Stock, Value, Issued, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, $0.001 par value (100,000,000 shares authorized, 34,970,709 and 33,914,652 shares issued and outstanding at March 31, 2025 and December 31, 2024, respectively)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LimitedPartnershipAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Limited Partnership Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LimitedPartnershipAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Limited Partnership Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_LimitedPartnershipAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Limited partnership agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentPercentageOfPreincentiveFeesNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment percentage of preincentive fees net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentPercentageOfPreincentiveFeesNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment Percentage of PreIncentive Fees Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentPercentageOfPreincentiveFeesNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payment percentage of preincentive fees net investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 A Supplemental Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 a supplemental second dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024ASupplementalSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 A Supplemental Second Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAndMoneyMarketFundsOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments and money market funds owned at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAndMoneyMarketFundsOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments and Money Market Funds Owned at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentsAndMoneyMarketFundsOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q3DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2025 Q3 Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q3DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2025 Q3 Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2025Q3DividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2025 Q3 Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Maturity, Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Special Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_SpecialDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Special dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administration Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Administration Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Administration agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies (Note 7)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NwsTechnologiesLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">NWS Technologies, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NwsTechnologiesLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NWS Technologies, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NwsTechnologiesLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">NWS Technologies, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average number of shares outstanding - diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant Accounting Policies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendsAndDistributionsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends and Distributions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendsAndDistributionsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends and Distributions [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DividendsAndDistributionsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends and distributions.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ExtinguishmentOfDebtGainLossPerShareNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized losses on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ExtinguishmentOfDebtGainLossPerShareNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Extinguishment of Debt, Gain (Loss), Per Share, Net of Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpensesRatioBeforeBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total expenses, before base management fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpensesRatioBeforeBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Expenses Ratio Before Base Management Fee Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_InvestmentCompanyExpensesRatioBeforeBaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company, expenses ratio before base management fee waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IsiPsgHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Isi Psg Holdings LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IsiPsgHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ISI PSG Holdings, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IsiPsgHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ISI PSG holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetInterestAndDividendIncomePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and dividend income paid-in-kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetInterestAndDividendIncomePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Interest And Dividend Income Paid-In-Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetInterestAndDividendIncomePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset, interest and dividend income paid-in-kind.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Balance, Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Principal Amount - Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IngCapitalLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ING Capital LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IngCapitalLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ING Capital Limited Liability Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IngCapitalLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ING Capital LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GMPHVACLLCDbaMcGeeHeatingAndAirLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">GMP HVAC, LLC (dba McGee Heating And Air, LLC) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GMPHVACLLCDbaMcGeeHeatingAndAirLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">GMP HVAC, LLC (dba McGee Heating And Air, LLC).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GMPHVACLLCDbaMcGeeHeatingAndAirLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">GMP HVAC, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfInvestmentsRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of Investments represented more than ten percentage of aggregate investment portfolio.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfInvestmentsRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of investments represented more than ten percentage of aggregate investment portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NumberOfInvestmentsRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Investments Represented More Than Ten Percentage of Aggregate Investment Portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net increase decrease in net assets resulting from operations to common stockholders diluted.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Increase Decrease in Net Assets Resulting from Operations to Common Stockholders Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net increase in net assets resulting from operations per share - diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MicronicsFiltrationHoldingsIncDbaMicronicsEngineeredFiltrationGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Micronics Filtration Holdings Inc Dba Micronics Engineered Filtration Group Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MicronicsFiltrationHoldingsIncDbaMicronicsEngineeredFiltrationGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Micronics Filtration Holdings Inc dba Micronics Engineered Filtration Group Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MicronicsFiltrationHoldingsIncDbaMicronicsEngineeredFiltrationGroupIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Micronics Filtration Holdings, Inc. (dba Micronics Engineered Filtration Group, Inc.).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedLossesOnExtinguishmentOfDebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Losses on Extinguishment of Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedLossesOnExtinguishmentOfDebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Losses On Extinguishment Of Debt Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedLossesOnExtinguishmentOfDebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized losses on extinguishment of debt policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesNortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States Northeast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesNortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">United States Northeast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_UnitedStatesNortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">United States Northeast.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RestaurantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restaurants Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RestaurantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restaurants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RestaurantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restaurants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedInvestmentGainsLossesOnEscrowSecuritiesNotHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized investment gains (losses) on escrow securities not held during period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedInvestmentGainsLossesOnEscrowSecuritiesNotHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Investment Gains Losses On Escrow Securities Not Held During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RealizedInvestmentGainsLossesOnEscrowSecuritiesNotHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Realized Gain (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investments, Fair Value Disclosure, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Incentive fee payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Income incentive fee payable - due to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncomeIncentiveFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">income incentive fee payable due to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GreenCubesTechnologyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Green Cubes Technology, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GreenCubesTechnologyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Green Cubes Technology, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_GreenCubesTechnologyLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Green Cubes Technology, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Carrying Value and Fair Value of Debt Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, by Balance Sheet Grouping [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ElementsBrandsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Elements Brands, LLC - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ElementsBrandsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Elements Brands, LLC - Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_ElementsBrandsLlcRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Elements Brands, LLC - revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Special Second Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Special Second Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Special Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from common stock offerings, net of expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentInKindIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PIK Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentInKindIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment In Kind Income Policy Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_PaymentInKindIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payment in kind income policy text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputEbitdaMultipleMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">EBITDA Multiples</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputEbitdaMultipleMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, EBITDA Multiple [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.341% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Three Four One Percent Interest Rate One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point three four one percent interest rate one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractualObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Commitment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractualObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contractual Obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractualObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contractual Obligation, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2023 A Special Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2023 A Special Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2023 A Special Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Investments, at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of restricted securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2024 Q3 Regular Dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2024 Q3 Regular Dividend [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Regular Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">O2024 Q3 Regular Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NonControlOrNonAffiliateInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-control/Non-affiliate Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NonControlOrNonAffiliateInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Control Or Non Affiliate Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_NonControlOrNonAffiliateInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non control or non affiliate investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdInfoParentIncDbaMediaradarRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ad Info Parent, Inc. (dba MediaRadar) - revolving loan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdInfoParentIncDbaMediaradarRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ad Info Parent, Inc. (dba MediaRadar) - Revolving Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AdInfoParentIncDbaMediaradarRevolvingLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ad Info Parent, Inc. (dba MediaRadar) - Revolving Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O 2024 Q3 Regular Second Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O 2024 Q3 Regular Second Dividends [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2024Q3RegularSecondDividendsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O 2024 Q3 Regular Second Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterimInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument interim interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterimInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Interim Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentInterimInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument interim interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesTreasuryStockReissued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Shares Purchased and Reissued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesTreasuryStockReissued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Treasury Stock Reissued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Financing Activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Financing Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LIABILITIES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommonAndPreferredEquityUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common And Preferred Equity Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommonAndPreferredEquityUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common and Preferred Equity Units [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_CommonAndPreferredEquityUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common and preferred equity units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Waiver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_WaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RaymondJamesAndAssociatesIncAndRobertWBairdAndCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Raymond James And Associates Inc And B. Riley Securities Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RaymondJamesAndAssociatesIncAndRobertWBairdAndCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Raymond James and Associates Inc and B. Riley Securities, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RaymondJamesAndAssociatesIncAndRobertWBairdAndCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Raymond James and Associates Inc and B. Riley Securities, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_RaymondJamesAndAssociatesIncAndRobertWBairdAndCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Raymond James &amp; Associates, Inc. and B. Riley Securities, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRepaymentsOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from sales and repayments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRepaymentsOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Repayments of) Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRepaymentsOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from (Repayments of) Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">O2023A Special Dividend One.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">O2023A Special Dividend One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_O2023ASpecialDividendOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">O2023A Special Dividend One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentIssuedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument issued amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentIssuedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Issued Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_DebtInstrumentIssuedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument issued amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MayeshWholesaleFloristLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mayesh Wholesale Florist, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MayeshWholesaleFloristLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mayesh Wholesale Florist, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MayeshWholesaleFloristLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mayesh Wholesale Florist, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncentiveFeeReversalCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fee (reversal) - capital gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncentiveFeeReversalCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee (Reversal) Capital Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_IncentiveFeeReversalCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fee (reversal) capital gains.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesHeldToMaturityNonaccrual_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesHeldToMaturityNonaccrual_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Held-to-Maturity, Nonaccrual</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MidwestTransitEquipmentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Midwest Transit Equipment, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MidwestTransitEquipmentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Midwest Transit Equipment, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_MidwestTransitEquipmentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Midwest transit equipment, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit facility commitment percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Commitment Fee Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointSevenThreeFivePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.735% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointSevenThreeFivePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Seven Three Five Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointSevenThreeFivePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point seven three five percent interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtAverageAmountOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average debt outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtAverageAmountOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Average Amount Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.341% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Three Four One Percent Interest Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointThreeFourOnePercentInterestRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point three four one percent interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 3 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BurgerfiInternationalLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BurgerFi International, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BurgerfiInternationalLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BurgerFi International, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BurgerfiInternationalLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BurgerFi International, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Events</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base management fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Base management fee waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Base Management Fee Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_BaseManagementFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Base management fee waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Five point zero eight two percent interest rate two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Five Point Zero Eight Two Percent Interest Rate Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_FivePointZeroEightTwoPercentInterestRateTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">5.082% Fixed Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregatePrincipalAmountOfPortfolioSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate principal amount sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregatePrincipalAmountOfPortfolioSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Principal Amount Of Portfolio Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_AggregatePrincipalAmountOfPortfolioSold_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate principal amount of portfolio sold.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_QedTechnologiesInternationalIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">QED Technologies International, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="fdus_QedTechnologiesInternationalIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">QED Technologies International, Inc [Member]</link:label>
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  <xsd:element id="fdus_AdministrationFeesPayableAndOtherDueToAffiliate" name="AdministrationFeesPayableAndOtherDueToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_O2023ASupplementalDividendThreeMember" name="O2023ASupplementalDividendThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_RestaurantsMember" name="RestaurantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_BaseManagementFeeWaiver" name="BaseManagementFeeWaiver" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_ElementsBrandsLlcMember" name="ElementsBrandsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MayeshWholesaleFloristLLCMember" name="MayeshWholesaleFloristLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_TotalDistribution" name="TotalDistribution" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_PartialLoanAndEquitySalesPolicyTextBlock" name="PartialLoanAndEquitySalesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_HaematologicTechnologiesIncMember" name="HaematologicTechnologiesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_WinonaFoodsIncMember" name="WinonaFoodsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DetechtionHoldingsLlcRevolvingLoanMember" name="DetechtionHoldingsLlcRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_November2026NotesMember" name="November2026NotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3DividendsOneMember" name="O2024Q3DividendsOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024ARegularThirdDividendsMember" name="O2024ARegularThirdDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3SupplementalSecondDividendsMember" name="O2024Q3SupplementalSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointZeroEightTwoPercentInterestRateOneMember" name="FivePointZeroEightTwoPercentInterestRateOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_LimitedPartnershipAgreementMember" name="LimitedPartnershipAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointEightSixOnePercentInterestRateMember" name="FivePointEightSixOnePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DividendsAndDistributionsAbstract" name="DividendsAndDistributionsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AeronixIncMember" name="AeronixIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FishbowlSolutionsLlcMember" name="FishbowlSolutionsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ThreePointFiveZeroPercentNotesDueTwoThousandTwentySixMember" name="ThreePointFiveZeroPercentNotesDueTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ThreePointTwoZeroNinePercentInterestRateMember" name="ThreePointTwoZeroNinePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InterestOnIdleFunds" name="InterestOnIdleFunds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_NetAssetValuePerShareOther" name="NetAssetValuePerShareOther" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_IncomeTaxProvisionBenefitFromRealizedGainsOnInvestments" name="IncomeTaxProvisionBenefitFromRealizedGainsOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfLoanOriginationFees" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfLoanOriginationFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2023ARegularDividendMember" name="O2023ARegularDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_WeightedAveragePriceOfCommonStockUnderAtTheMarketProgram" name="WeightedAveragePriceOfCommonStockUnderAtTheMarketProgram" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_EnvironmentalIndustriesMember" name="EnvironmentalIndustriesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FourPointFiveThreeThreePercentInterestRateMember" name="FourPointFiveThreeThreePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ProceedsFromSalesAndRepaymentsOfInvestments" name="ProceedsFromSalesAndRepaymentsOfInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_CommissionsUnderAtTheMarketProgram" name="CommissionsUnderAtTheMarketProgram" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2023ASupplementalDividendsMember" name="O2023ASupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MayeshWholesaleFloristLLCFirstLienDebtMember" name="MayeshWholesaleFloristLLCFirstLienDebtMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_IncreaseDecreaseInIncomeIncentiveFeePayableDueToAffiliate" name="IncreaseDecreaseInIncomeIncentiveFeePayableDueToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_CPCommunicationsLLCMember" name="CPCommunicationsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AllrediLlcMember" name="AllrediLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UnitedStatesMidwestMember" name="UnitedStatesMidwestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentVariableIndexFloorRate" name="InvestmentVariableIndexFloorRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_CumulativeUnderwritingFeesAndCommissionAndOfferingCosts" name="CumulativeUnderwritingFeesAndCommissionAndOfferingCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_EquityInvestmentMember" name="EquityInvestmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_W50HoldingsLlcPreferredEquityMember" name="W50HoldingsLlcPreferredEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2025Q2DividendsMember" name="O2025Q2DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_CapitalGainsIncentiveFeeAccruedReversed" name="CapitalGainsIncentiveFeeAccruedReversed" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_O2023ASpecialThirdDividendsMember" name="O2023ASpecialThirdDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_EstexManufacturingCompanyLlcMember" name="EstexManufacturingCompanyLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ARegularThirdDividendsMember" name="O2023ARegularThirdDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UnitedStatesWestMember" name="UnitedStatesWestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_TwoPointSevenNineThreePercentInterestRateMember" name="TwoPointSevenNineThreePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_WrittenNoticePeriodForTerminationOfAgreement" name="WrittenNoticePeriodForTerminationOfAgreement" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PercentageOfNetCapitalGains" name="PercentageOfNetCapitalGains" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2023ASpecialDividendsMember" name="O2023ASpecialDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_IncomeIncentiveFeesPayableDueToAffiliate" name="IncomeIncentiveFeesPayableDueToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_ProceedsReceivedFromRepaymentsOfSecuredBorrowingsNet" name="ProceedsReceivedFromRepaymentsOfSecuredBorrowingsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_SeniorAssetCoverageRatio" name="SeniorAssetCoverageRatio" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FivePointThreeOneZeroPercentInterestRateMember" name="FivePointThreeOneZeroPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3SupplementalDividendTwoMember" name="O2024Q3SupplementalDividendTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3SupplementalFirstDividendsMember" name="O2024Q3SupplementalFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_CommitmentsOutstandingToFundVariousUndrawnRevolvingLoansOtherDebtInvestmentsAndCapitalCommitments" name="CommitmentsOutstandingToFundVariousUndrawnRevolvingLoansOtherDebtInvestmentsAndCapitalCommitments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_InvestmentCompanyPortfolioTurnoverRatio" name="InvestmentCompanyPortfolioTurnoverRatio" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ThrustFlightLlcFirstLienDebtMember" name="ThrustFlightLlcFirstLienDebtMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023Q4DividendsMember" name="O2023Q4DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UpgCompanyLlcMember" name="UpgCompanyLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UnitedStatesSoutheastMember" name="UnitedStatesSoutheastMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentIncomeExpenseNetAfterTax" name="InvestmentIncomeExpenseNetAfterTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_AffiliateInvestmentMember" name="AffiliateInvestmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DebtIssueCosts" name="DebtIssueCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_IncreaseDecreaseInReceivablesFromInvestmentsSold" name="IncreaseDecreaseInReceivablesFromInvestmentsSold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_PercentageOfNetCapitalGainsRealized" name="PercentageOfNetCapitalGainsRealized" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_BusinessServicesMember" name="BusinessServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AccruedInterestAndFeesPayable" name="AccruedInterestAndFeesPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_PaymentsOfDividendsIncludingExpenses" name="PaymentsOfDividendsIncludingExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_IncomeIncentiveFee" name="IncomeIncentiveFee" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_VirtexEnterprisesLpMember" name="VirtexEnterprisesLpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SecuredBorrowingsMember" name="SecuredBorrowingsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DeferredUpfrontFees" name="DeferredUpfrontFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_PercentageOfEquityInvestmentsHeldInPortfolioCompanies" name="PercentageOfEquityInvestmentsHeldInPortfolioCompanies" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_InterestAndDividendIncomePaidInKind" name="InterestAndDividendIncomePaidInKind" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_PercentageOfPublicOfferingPrice" name="PercentageOfPublicOfferingPrice" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_WarrantOrRightsPercentageOfOutstandingDebtPrincipalToPurchase" name="WarrantOrRightsPercentageOfOutstandingDebtPrincipalToPurchase" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetProceedsFromLoanOriginationFees" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetProceedsFromLoanOriginationFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_TwoKDirectIncMember" name="TwoKDirectIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointThreeFourOnePercentInterestRateTwoMember" name="FivePointThreeFourOnePercentInterestRateTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024ASupplementalSecondDividendsMember" name="O2024ASupplementalSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DebtInstrumentIssuedAmount" name="DebtInstrumentIssuedAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2025Q1DividendsMember" name="O2025Q1DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentRiskPolicyTextBlock" name="InvestmentRiskPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FivePointThreeFourOnePercentInterestRateOneMember" name="FivePointThreeFourOnePercentInterestRateOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ApmIntermediateHoldingsLlcMember" name="ApmIntermediateHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NetUnrealizedAppreciationDepreciationOnInvestments" name="NetUnrealizedAppreciationDepreciationOnInvestments" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PayEntryFinancialServicesIncMember" name="PayEntryFinancialServicesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AdministrativeServiceExpenses" name="AdministrativeServiceExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_SecuredBorrowings" name="SecuredBorrowings" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_O2024ASupplementalDividendsMember" name="O2024ASupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_GrossInvestmentIncomeAbstract" name="GrossInvestmentIncomeAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_IncreaseDecreaseInPayablesForInvestmentsPurchased" name="IncreaseDecreaseInPayablesForInvestmentsPurchased" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_PercentageOfExciseTax" name="PercentageOfExciseTax" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FivePointZeroEightTwoPercentInterestRateFourMember" name="FivePointZeroEightTwoPercentInterestRateFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3SupplementalDividendsMember" name="O2024Q3SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UsGreenfiberLlcMember" name="UsGreenfiberLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NumberOfInvestmentPorfolioCompanies" name="NumberOfInvestmentPorfolioCompanies" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_SummaryOfUnamortizedDeferredFinancingCostsTableTextBlock" name="SummaryOfUnamortizedDeferredFinancingCostsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2024Q3RegularFirstDividendsMember" name="O2024Q3RegularFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_StockRepurchaseProgramPolicyTextBlock" name="StockRepurchaseProgramPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ConsumerProductsSectorMember" name="ConsumerProductsSectorMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ChoiceTechnologySolutionsLlcDbaChoiceMerchantSolutionsLlcRevolvingLoanMember" name="ChoiceTechnologySolutionsLlcDbaChoiceMerchantSolutionsLlcRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PercentageOfVotingSecurities" name="PercentageOfVotingSecurities" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2023ARegularFirstDividendsMember" name="O2023ARegularFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NonAccrualPolicyTextBlock" name="NonAccrualPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FivePointZeroEightTwoPercentInterestRateTwoMember" name="FivePointZeroEightTwoPercentInterestRateTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ManagementFeesAnnualRatePercentage" name="ManagementFeesAnnualRatePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_GrossProceedsFromIssuanceOfCommonStockUnderAtTheMarketProgram" name="GrossProceedsFromIssuanceOfCommonStockUnderAtTheMarketProgram" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2024ASupplementalThirdDividendsMember" name="O2024ASupplementalThirdDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AssetCoverageRatio" name="AssetCoverageRatio" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_DebtInstrumentInterestRatePercentageBasedOnPriorToCertainConditionsSatisfied" name="DebtInstrumentInterestRatePercentageBasedOnPriorToCertainConditionsSatisfied" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2023ARegularDividendOneMember" name="O2023ARegularDividendOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PaymentPercentageOfPreincentiveFeesNetInvestmentIncome" name="PaymentPercentageOfPreincentiveFeesNetInvestmentIncome" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_DebtInstrumentMaturityYearRangeEnd" name="DebtInstrumentMaturityYearRangeEnd" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_IncreaseDecreaseAdministrationFeePayableAndOtherDueToFromAffiliate" name="IncreaseDecreaseAdministrationFeePayableAndOtherDueToFromAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_FidusEquityFundILimitedPartnershipMember" name="FidusEquityFundILimitedPartnershipMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_OnepathSystemsLlcMember" name="OnepathSystemsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentCompanyExpensesRatioBeforeBaseManagementFeeWaiver" name="InvestmentCompanyExpensesRatioBeforeBaseManagementFeeWaiver" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_GMPHVACLLCDbaMcGeeHeatingAndAirLLCMember" name="GMPHVACLLCDbaMcGeeHeatingAndAirLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentVariableIndexSpreadRate" name="InvestmentVariableIndexSpreadRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2025Q1RegularSecondDividendsMember" name="O2025Q1RegularSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UnitrancheInvestmentsMember" name="UnitrancheInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023Q3DividendsMember" name="O2023Q3DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_CommonEquityMember" name="CommonEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SupplementalDividendMember" name="SupplementalDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DelayedDrawCommitmentFourMember" name="DelayedDrawCommitmentFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ThreePointOneNineZeroPercentInterestRateMember" name="ThreePointOneNineZeroPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2025Q3DividendsTwoMember" name="O2025Q3DividendsTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SbicDebentureProgramMaximumAmountOutstandingSbaDebentures" name="SbicDebentureProgramMaximumAmountOutstandingSbaDebentures" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_SixPointSevenFivePercentNotesDueTwoThousandAndThirtyMember" name="SixPointSevenFivePercentNotesDueTwoThousandAndThirtyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AcendreMidcoIncRevolvingLoanMember" name="AcendreMidcoIncRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InformationTechnologyServicesMember" name="InformationTechnologyServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DealerbuiltAcquisitionLlcMember" name="DealerbuiltAcquisitionLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PercentageOfInvestmentCompanyTaxableIncome" name="PercentageOfInvestmentCompanyTaxableIncome" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_BedfordPrecisionPartsLLCMember" name="BedfordPrecisionPartsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FirstLienDebtMember" name="FirstLienDebtMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DebtInstrumentInterestRatePercentageBasedOnAfterCertainConditionsSatisfied" name="DebtInstrumentInterestRatePercentageBasedOnAfterCertainConditionsSatisfied" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_BpThriftBuyerLlcMember" name="BpThriftBuyerLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AccruedAdministrativeServiceExpensePayable" name="AccruedAdministrativeServiceExpensePayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_RepaymentsOfSmallBusinessAdministrationDebentures" name="RepaymentsOfSmallBusinessAdministrationDebentures" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_LaboratoryTestingLLCMember" name="LaboratoryTestingLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentMaturityPeriod" name="InvestmentMaturityPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_InvestmentRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio" name="InvestmentRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2024Q3DividendsTwoMember" name="O2024Q3DividendsTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2025Q3DividendsOneMember" name="O2025Q3DividendsOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UnitedStatesSouthwestMember" name="UnitedStatesSouthwestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PercentageOfCapitalGainsIncentiveFeeAccrued" name="PercentageOfCapitalGainsIncentiveFeeAccrued" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AggregatePrincipalAmountOfPortfolioSold" name="AggregatePrincipalAmountOfPortfolioSold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_K2MergerAgreementAgentLlcMember" name="K2MergerAgreementAgentLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3DividendsMember" name="O2024Q3DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FidusInvestmentAdvisorsLlcMember" name="FidusInvestmentAdvisorsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PercentageOfPortfolioInvestmentsAtFairValue" name="PercentageOfPortfolioInvestmentsAtFairValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2024Q3SupplementalDividendMember" name="O2024Q3SupplementalDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MidwestTransitEquipmentIncMember" name="MidwestTransitEquipmentIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASupplementalDividendTwoMember" name="O2023ASupplementalDividendTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DividendOneMember" name="DividendOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentCompanyBaseManagementFeeWaiver" name="InvestmentCompanyBaseManagementFeeWaiver" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FirstLienDebtOneMember" name="FirstLienDebtOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023Q1DividendsMember" name="O2023Q1DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SeniorSecuredRevolvingCreditFacilityMember" name="SeniorSecuredRevolvingCreditFacilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_StewardHoldingLlcMember" name="StewardHoldingLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_HilcoPlasticsHoldingsLlcMember" name="HilcoPlasticsHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_OriginationAndClosingFee" name="OriginationAndClosingFee" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ValuationTechniqueEnterpriseValueWaterfallMember" name="ValuationTechniqueEnterpriseValueWaterfallMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASpecialDividendOneMember" name="O2023ASpecialDividendOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_TwoPointOneSevenTwoPercentInterestRateMember" name="TwoPointOneSevenTwoPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SmallBusinessAdministrationDebenturesMember" name="SmallBusinessAdministrationDebenturesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InfoTechOperatingLLCMember" name="InfoTechOperatingLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FishbowlSolutionsLLCRevolvingLoanMember" name="FishbowlSolutionsLLCRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointNineEightThreePercentInterestRateMember" name="FivePointNineEightThreePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasicAndDiluted" name="NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasicAndDiluted" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_IsiPsgHoldingsLlcMember" name="IsiPsgHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024Q3SupplementalDividendOneMember" name="O2024Q3SupplementalDividendOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ProceedsReceivableFromStockOffering" name="ProceedsReceivableFromStockOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2023ARegularDividendsMember" name="O2023ARegularDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_CardboardBoxLlcDbaAnthonysCoalFiredPizzaMember" name="CardboardBoxLlcDbaAnthonysCoalFiredPizzaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MedsurantHoldingsLlcMember" name="MedsurantHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SuitedConnectorLlcMember" name="SuitedConnectorLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NwsTechnologiesLlcMember" name="NwsTechnologiesLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InvestmentsAsPercentageOfAssets" name="InvestmentsAsPercentageOfAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_RaymondJamesAndAssociatesIncAndRobertWBairdAndCoMember" name="RaymondJamesAndAssociatesIncAndRobertWBairdAndCoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PercentageOfTaxableIncome" name="PercentageOfTaxableIncome" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_InvestmentCompanyInvestmentIncomeLossPeriodIncreaseDecrease" name="InvestmentCompanyInvestmentIncomeLossPeriodIncreaseDecrease" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AdditionalInterestRateOnInvestmentsPaidInKind" name="AdditionalInterestRateOnInvestmentsPaidInKind" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ThreePointTwoSixZeroPercentInterestRateMember" name="ThreePointTwoSixZeroPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MesaLineServicesLlcMember" name="MesaLineServicesLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_BorrowingsUnderCreditFacilityNetOfDeferredFinancingCosts" name="BorrowingsUnderCreditFacilityNetOfDeferredFinancingCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_MeasurementInputVolatilityOfCreditMember" name="MeasurementInputVolatilityOfCreditMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointNineEightEightPercentInterestRateMember" name="FivePointNineEightEightPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_LineOfCreditFacilityMinimumUtilizationCommitmentFeePercentage" name="LineOfCreditFacilityMinimumUtilizationCommitmentFeePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_FairValueAssetsLevelOneToLevelTwoTransfersAmount" name="FairValueAssetsLevelOneToLevelTwoTransfersAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_IncreaseDecreaseInBaseManagementFeePayable" name="IncreaseDecreaseInBaseManagementFeePayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_DividendTwoMember" name="DividendTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_Percentageoffairvalue" name="Percentageoffairvalue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2023Q2DividendsMember" name="O2023Q2DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SixPointSevenFivePercentNotesDueTwoThousandTwentySixMember" name="SixPointSevenFivePercentNotesDueTwoThousandTwentySixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_TediaCompanyLlcMember" name="TediaCompanyLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DelayedDrawCommitmentTwoMember" name="DelayedDrawCommitmentTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SecondLienDebtMember" name="SecondLienDebtMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointZeroEightTwoPercentInterestRateMember" name="FivePointZeroEightTwoPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ARegularDividendTwoMember" name="O2023ARegularDividendTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ComponentManufacturingMember" name="ComponentManufacturingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MaximumAggregateOfferingPriceOfCommonStockUnderAtTheMarketProgram" name="MaximumAggregateOfferingPriceOfCommonStockUnderAtTheMarketProgram" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_AmeriwaterLlcMember" name="AmeriwaterLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DeferredFinancingCostsPolicyTextBlock" name="DeferredFinancingCostsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_MeasurementInputWeightedAverageCostOfCapitalMember" name="MeasurementInputWeightedAverageCostOfCapitalMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_OnePointThreeNineEightPercentInterestRateMember" name="OnePointThreeNineEightPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_HealthcareServicesMember" name="HealthcareServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_IncreaseDecreaseInAccruedInterestAndFeesPayable" name="IncreaseDecreaseInAccruedInterestAndFeesPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_SixPointZeroFourSevenPercentInterestRateMember" name="SixPointZeroFourSevenPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_BurgerfiInternationalLlcMember" name="BurgerfiInternationalLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PreIncentiveFeeFixedHurdleRate" name="PreIncentiveFeeFixedHurdleRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_WaiverMember" name="WaiverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024ASupplementalFirstDividendsMember" name="O2024ASupplementalFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_GarlockPrintingAndConvertingOperationsLlcMember" name="GarlockPrintingAndConvertingOperationsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PercentageOfAmountOfPreIncentiveFeeNetInvestmentIncome" name="PercentageOfAmountOfPreIncentiveFeeNetInvestmentIncome" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBOneMember" name="PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLBOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASupplementalFirstDividendsMember" name="O2023ASupplementalFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_CapitalGainsIncentiveFeePayableDueToAffiliate" name="CapitalGainsIncentiveFeePayableDueToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_ExpensesNetOfBaseManagementFeeWaiver" name="ExpensesNetOfBaseManagementFeeWaiver" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_AverageDebtPerShare" name="AverageDebtPerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_InvestmentCompanyDistributionsFromCapitalGainsPerShare" name="InvestmentCompanyDistributionsFromCapitalGainsPerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AmericanAllwasteLlcMember" name="AmericanAllwasteLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FirstLienDebtSixMember" name="FirstLienDebtSixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AverageFullyDilutedEquityOwnershipPercentage" name="AverageFullyDilutedEquityOwnershipPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_IncentiveFeeReversalCapitalGains" name="IncentiveFeeReversalCapitalGains" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2025Q2SupplementalDividendsMember" name="O2025Q2SupplementalDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MoneyMarketFundsInterestRatePaidInKind" name="MoneyMarketFundsInterestRatePaidInKind" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PaymentInKindIncomePolicyTextBlock" name="PaymentInKindIncomePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2024Q4DividendsMember" name="O2024Q4DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SummaryOfCommonStockAtmProgram1TableTextBlock" name="SummaryOfCommonStockAtmProgram1TableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_InterestAndDividendIncomePolicyTextBlock" name="InterestAndDividendIncomePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_RealizedLossesOnExtinguishmentOfDebtPolicyTextBlock" name="RealizedLossesOnExtinguishmentOfDebtPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AdInfoParentIncDbaMediaradarRevolvingLoanMember" name="AdInfoParentIncDbaMediaradarRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FairValueAssetsLevelTwoToLevelOneTransfersAmount" name="FairValueAssetsLevelTwoToLevelOneTransfersAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" name="PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_O2023ASupplementalDividendOneMember" name="O2023ASupplementalDividendOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DividendReinvestmentPlanMember" name="DividendReinvestmentPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_QedTechnologiesInternationalIncMember" name="QedTechnologiesInternationalIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AutoCrmLlcMember" name="AutoCrmLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_BuildingProductsManufacturingMember" name="BuildingProductsManufacturingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DebtInstrumentMaturityYearRangeStart1" name="DebtInstrumentMaturityYearRangeStart1" type="xbrli:gYearItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AccretionOfLoanOriginationFees" name="AccretionOfLoanOriginationFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_FeeIncomePolicyTextBlock" name="FeeIncomePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PrimeAeGroupIncMember" name="PrimeAeGroupIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_RealizedGainsOrLossesAndUnrealizedAppreciationOrDepreciationOnInvestmentsPolicyTextBlock" name="RealizedGainsOrLossesAndUnrealizedAppreciationOrDepreciationOnInvestmentsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_March2030NotesMember" name="March2030NotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_GreenCubesTechnologyLlcMember" name="GreenCubesTechnologyLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_CumulativeGrossProceedsFromIssuanceOfCommonStock" name="CumulativeGrossProceedsFromIssuanceOfCommonStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_ControlInvestmentsMember" name="ControlInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASpecialDividendThreeMember" name="O2023ASpecialDividendThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_WonderwareHoldingsLlcDbaCoreBusinessTechnologiesMember" name="WonderwareHoldingsLlcDbaCoreBusinessTechnologiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_IncomeIncentiveFeePayable" name="IncomeIncentiveFeePayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_InvestmentCompanyExpenseRatioToAverageNetAssets" name="InvestmentCompanyExpenseRatioToAverageNetAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AppliedDataCorporationMember" name="AppliedDataCorporationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NetChangeInUnrealizedAppreciationDepreciationOnInvestments" name="NetChangeInUnrealizedAppreciationDepreciationOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_O2023ARegularSecondDividendsMember" name="O2023ARegularSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DebtInvestmentInNumberOfPortfolioCompaniesOnNonAccrualStatus" name="DebtInvestmentInNumberOfPortfolioCompaniesOnNonAccrualStatus" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ProceedsReceivedFromSmallBusinessAdministrationDebentures" name="ProceedsReceivedFromSmallBusinessAdministrationDebentures" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2024Q3RegularSecondDividendsMember" name="O2024Q3RegularSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_DiversifiedSearchLlcMember" name="DiversifiedSearchLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ElementsBrandsLlcRevolvingLoanMember" name="ElementsBrandsLlcRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_Debentures" name="Debentures" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_SpecialtyDistributionMember" name="SpecialtyDistributionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_LineOfCreditFacilityRemainingUnusedCapacityCommitmentFeePercentage" name="LineOfCreditFacilityRemainingUnusedCapacityCommitmentFeePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_DebtInstrumentPoolingDate" name="DebtInstrumentPoolingDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ConsumerServicesMember" name="ConsumerServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_WorldToursLLCMember" name="WorldToursLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointEightSixOnePercentInterestRateTwoMember" name="FivePointEightSixOnePercentInterestRateTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SummaryOfCommonStockTableTextBlock" name="SummaryOfCommonStockTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PreferredEquityMember" name="PreferredEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ADividendsMember" name="O2023ADividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MoneyMarketFundsAtFairValue" name="MoneyMarketFundsAtFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_InvestmentIncomeFeeIncome" name="InvestmentIncomeFeeIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_UtilitiesServicesMember" name="UtilitiesServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PugetCollisionLLCMember" name="PugetCollisionLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AverageNetAssets" name="AverageNetAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_InvestmentCompanyDividendsToStockholdersPerShare" name="InvestmentCompanyDividendsToStockholdersPerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAOneMember" name="PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NetbaseSolutionsIncMember" name="NetbaseSolutionsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointFourThreeNinePercentInterestRateTwoMember" name="FivePointFourThreeNinePercentInterestRateTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASupplementalSecondDividendsMember" name="O2023ASupplementalSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MoneyMarketFundsInterestRatePaidInCash" name="MoneyMarketFundsInterestRatePaidInCash" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_MicronicsFiltrationHoldingsIncDbaMicronicsEngineeredFiltrationGroupIncMember" name="MicronicsFiltrationHoldingsIncDbaMicronicsEngineeredFiltrationGroupIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_UnderwritingDiscounts" name="UnderwritingDiscounts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_CustomerExpressionsCorpMember" name="CustomerExpressionsCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASupplementalThirdDividendsMember" name="O2023ASupplementalThirdDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASpecialFirstDividendsMember" name="O2023ASpecialFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_Percentageofcost" name="Percentageofcost" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_MeasurementInputAssetCoverageMember" name="MeasurementInputAssetCoverageMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_OwnershipPercentageOfOutstandingVotingSecuritiesInPortfolioInvestment" name="OwnershipPercentageOfOutstandingVotingSecuritiesInPortfolioInvestment" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_CommonAndPreferredEquityUnitsMember" name="CommonAndPreferredEquityUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024ARegularFirstDividendsMember" name="O2024ARegularFirstDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SeniorSecuredRevolvingCreditAgreementMember" name="SeniorSecuredRevolvingCreditAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASupplementalDividendMember" name="O2023ASupplementalDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_SupplementalDividendTwoMember" name="SupplementalDividendTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_January2026NotesMember" name="January2026NotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024ARegularSecondDividendsMember" name="O2024ARegularSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2025Q2RegularDividendsMember" name="O2025Q2RegularDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AerospaceAndDefenseManufacturingMember" name="AerospaceAndDefenseManufacturingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasic" name="NetIncreaseDecreaseInNetAssetsResultingFromOperationsToCommonStockholdersBasic" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_RevolvingLoanMember" name="RevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetInterestAndDividendIncomePaidInKind" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetInterestAndDividendIncomePaidInKind" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_O2023ASupplementalFourthDividendsMember" name="O2023ASupplementalFourthDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAMember" name="PayEntryFinancialServicesIncDbaPayentry-SecondLienDDTLAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointSevenThreeFivePercentInterestRateMember" name="FivePointSevenThreeFivePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfOriginalIssueDiscount" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAccretionOfOriginalIssueDiscount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_WarrantsNotesMember" name="WarrantsNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASpecialDividendTwoMember" name="O2023ASpecialDividendTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_InterestEarningOnUnfundedBalanceCommitment" name="InterestEarningOnUnfundedBalanceCommitment" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_TwoPointThreeSevenSevenPercentInterestRateMember" name="TwoPointThreeSevenSevenPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointFourthreeNinePercentInterestRateMember" name="FivePointFourthreeNinePercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_WesternsSmokehouseLlcMember" name="WesternsSmokehouseLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AffiliateInvestmentsMember" name="AffiliateInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointEightSixOnePercentInterestRateThreeMember" name="FivePointEightSixOnePercentInterestRateThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AdditionalInterestRateOnInvestments" name="AdditionalInterestRateOnInvestments" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_SupplementalDividendOneMember" name="SupplementalDividendOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_FivePointThreeFourOnePercentInterestRateThreeMember" name="FivePointThreeFourOnePercentInterestRateThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NumberOfInvestmentsRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio" name="NumberOfInvestmentsRepresentedMoreThanTenPercentageOfAggregateInvestmentPortfolio" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="fdus_ShareValueAvailableUnderAtTheMarketProgram" name="ShareValueAvailableUnderAtTheMarketProgram" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_FivePointZeroEightTwoPercentInterestRateThreeMember" name="FivePointZeroEightTwoPercentInterestRateThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ARegularDividendThreeMember" name="O2023ARegularDividendThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2023ASpecialDividendMember" name="O2023ASpecialDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_RealizedInvestmentGainsLossesOnEscrowSecuritiesNotHeldDuringPeriod" name="RealizedInvestmentGainsLossesOnEscrowSecuritiesNotHeldDuringPeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_O2025Q3DividendsMember" name="O2025Q3DividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_NumberOfResidualInvestmentPorfolioCompanies" name="NumberOfResidualInvestmentPorfolioCompanies" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="fdus_AggregateAmountOfCapitalGainsIncentiveFees" name="AggregateAmountOfCapitalGainsIncentiveFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_FivePointFourThreeNinePercentInterestRateOneMember" name="FivePointFourThreeNinePercentInterestRateOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_MirageTrailersLlcMember" name="MirageTrailersLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_LevelEducationGroupLlcMember" name="LevelEducationGroupLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AccruedCapitalGainsIncentiveFeePayable" name="AccruedCapitalGainsIncentiveFeePayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_AxisMedicalTechnologiesLLCDbaMoveMedicalRevolvingLoanMember" name="AxisMedicalTechnologiesLLCDbaMoveMedicalRevolvingLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_AmortizationOfDeferredEquityFinancingCosts" name="AmortizationOfDeferredEquityFinancingCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="fdus_RealizedGainsLossesOnExtinguishmentOfDebt" name="RealizedGainsLossesOnExtinguishmentOfDebt" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="fdus_ApplegateGreenfiberIntermediateIncMember" name="ApplegateGreenfiberIntermediateIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_ThreePointTwoSixSevenPercentInterestRateMember" name="ThreePointTwoSixSevenPercentInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2024ADividendsMember" name="O2024ADividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="fdus_O2025Q1SupplementalSecondDividendsMember" name="O2025Q1SupplementalSecondDividendsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
</xsd:schema>
