《光通信技術(shù)》課件：Lecture4

DepartmentofOpticalEngineeringFiberFabricationTwoMajorStages:PreformfabricationHydrolysisreactionsHeatingsource:Oxyhydrogenflame,microwaveReactions:FiberdrawingDepartmentofOpticalEngineeringDopantsforchangingrefractiveindexMaterial Max.(%)

3.5

1.2

-0.5 -0.7

DepartmentofOpticalEngineeringModernPreformFabricationChemicalVaporDepositionFlameenhancedorPlasmaenhancedModifiedChemicalVapor(MCVD)OutsideVaporDeposition(OVD)Vapor-phaseAxialDeposition(VAD)ToughrequirementstomeetPrecisedimensions:diametercontroloverlonglengthAccuraterefractiveindexprofilelengthwiseDepartmentofOpticalEngineeringModifiedChemicalVaporDeposition(MCVD)

DepartmentofOpticalEngineeringFabricationProcessStep1Sootpreparation:0.1-0.5micrometerindiameterSiO2particlesdepositionStep2Sintering:meltfineSiO2particlestogetherandremoveallbubblesStep3Stretching:pullpreformtoadesiredsizewithhighprecisionDepartmentofOpticalEngineeringPlasmaChemicalVaporDeposition(PVCD)DepartmentofOpticalEngineeringVaporphaseaxialdeposition(VAD)DepartmentofOpticalEngineeringConsolidation/vitrification/sinteringSinteringProcess:Flushheliumathightemperature(1450deg.C)DepartmentofOpticalEngineeringState-of-artVADdepositionDoubleflamehigh-efficientdepositionsystemLaserbeammonitor/controlofdepositionprocessLaserBeamCoreroddepositionCladdingdepositionDepartmentofOpticalEngineeringStretching/CladdingDepositionPreparationStretchingProcess:Stretchingpreformathightemperature(1200deg.C)withareal-timediametercontrolbyalasermicrometerDepartmentofOpticalEngineeringOVDDevelopedbyCorningin1972Firstsucessfulmass-fabricationprocessReactions(hydrolysis)Consistsoffourphases:LaydownMandrelremovalConsolidationStretchingDepartmentofOpticalEngineeringOutsideVaporDeposition(OVD)DepartmentofOpticalEngineeringDrawingandSpoolingDepartmentofOpticalEngineeringFiberPullingProcess

FiberPullingSpeed:1200m/minElectricGraphiteFurnace(2200-2300C)PreformDepartmentofOpticalEngineeringFiberCoatingsMainfunctionsofthecoating:ProtectthefiberfromanyexternaldamageFeaturesofthecoatingAdhesionAbilitytobestripped(1.4-4.2N)ToughnessYoung’smodulus1.8Mpaforsoftand800MpaforhardcoatingMoistureresistanceGlasstransitiontemperatureTgTheglass–liquidtransitionisthereversibletransitioninamorphousmaterialsfromahard/brittlestateintoamoltenorrubber-likestate.T>Tg,allowingmolecularchainstoslidepasteachotherwhenaforceisapplied.DepartmentofOpticalEngineeringFibers/FiberribbonsDepartmentofOpticalEngineeringFiber-OpticCablesBasicStructureStrengthMemberPlasticBuffertubeLoosebufferTightbufferOuterjacketarmored/nonarmoredDepartmentofOpticalEngineeringFiberCableDesignsLoosetubeminibundlecablePolyethylene(PE)outersheathTape/ripcordsWater-blockinggelDielectricstrengthmemberLoosebuffertubeFibers/fiberribbonsDepartmentofOpticalEngineeringReadingdatasheetsOperating-temperature -40to70oCFibercounts 2-60Maximumfiberspertube 12Numberofactivetubes 5Numberoftubepositions 5Nominalweight 438kg/kmNominalouterdiameter 14.5mmMinimumbendingradius 22.5cmMaximumtensileload 1000NTransmissioncharacteristicsMaximumattenuation 3/1.4dB/kmTypicalattenuationMinimumbandwidth 400MHz/kmDepartmentofOpticalEngineeringFiberConnectorizationSplicing(Tojoin,permanently,physicalmediathatconductortransmitpoweroracommunicationsignal.2.Adevicethatsojoinsconductingortransmittingmedia.3.Thecompletedjoint.)MechanicalFusionDepartmentofOpticalEngineeringIntrinsicConnectionlossesIntrinsiclossesCorediametermismatch Loss=-10log(a2/a1)2Numericalaperturemismatch Loss=-10log(NA2/NA1)2Mode-field-diametermismatch Loss=-10log(4/(w2/w1+w1/w2)2)DepartmentofOpticalEngineeringExtrinsicConnectionlossesExtrinsiclosses:MMGIv.s.SMfiberLateralmisalignment

Angularmisalignment

Endseparation

DepartmentofOpticalEngineeringLateralmisalignmentDepartmentofOpticalEngineeringAngularmisalignmentDepartmentofOpticalEngineeringEndSeparationDepartmentofOpticalEngineeringReflectionlossDefinition:RL(dB)=10logR,R=Pref/Pin=((n1-n2)/(n1+n2))2Oneair-coresurface n1=1,n2=1.46Reflectionloss=-14.5dBAirgaploss:twobeams

DepartmentofOpticalEngineeringConnectorsConnectortypesFC/PC,FC/APCLCMUDepartmentofOpticalEngineeringTechnicalrequirementsDepartmentofOpticalEngineeringPowerBudgetandbandwidthPowerbudget:calculatethepoweratreceivingendandknowsthelossallocationsalongthelinkUsedBmanddBBandwidthCheckdatasheet/manufacturer’srecommendationUserise-