宽带光接入网复习

POS:PassiveOpticalSplitterONU:OpticalNetworkUnitRN:RemoteNodeCO:CentralOfficeEU:End-User1.WDMPONvsTDM-PONadvantageanddisadvantage?优势：Apassiveopticalnetwork(PON)isaformoffiber-opticaccessnetworkthatusespoint-to-multipointfibertothepremisesinwhichunpoweredopticalsplittersareusedtoenableasingleopticalfibertoservemultiplepremises.APONconsistsofanopticallineterminal(OLT)attheserviceprovider'scentralofficeandanumberofopticalnetworkunits(ONUs)nearendusers.APONreducestheamountoffiberandcentralofficeequipmentrequiredcomparedwithpoint-to-pointarchitectures.ForWDM-PONAdvantage:1)、Higherbandwidth:dedicatedbandwidthforeachONU(nosharingasinTDM)；2)、ReceiversatONUsonlyoperateatchannelrate,(c.f.thereceiverateachONUinTDMnetworkhastooperateattheaggregatedrate)；3)、Flexible:datarateoneachwavelengthchannelcanbedifferentandcanbeeasilyscaledup,dynamicbandwidthallocationispossible；4)Norangingorcollisionavoidanceschemeforupstreampath；5)Simplewavelengthroutingisallowed；6)easytolocalizethefaultusingOTDR；7)Bitrateisunlimitedandprotocolistransparent.Disadvantage:1)、HighercostsoflasersandWDMcomponents;2)、Requirewavelengthmanagement；3)、Temperaturecontrolisanotherchallengebecauseofwavelengthstendtodriftwithenvironmentaltemperatures.ForTDM-PONAdvantage:1)Widelyapplied.ThevastmajorityofPONsystemsdeployedtodayareTDMbasedPONsystems(i.e.,B-PON,E-PON,andG-PON);2)Theyalmostexclusivelyoperateonasinglefiber.Disadvantage:1)ThebandwidthinTDM-PONislimited;2)thereceiverateachONUinTDMnetworkhastooperateattheaggregatedrate;3)difficulttolocalizethefaultusingOTDR;4)bitratehardtobeyond10Gb/sandprotocolisnottransparent.2、WDM-PONbasicconfiguration,upstreamtransmissionandcolorlessONUdesign?WDM-PON的基本结构ColorlessONU技术ColorlessONUmeansthecomponentsattheONUisindependentofthedownstream/upstreamwavelengths.ThusallONUcanbeidenticalandthecostofmanufacturingandtestingcanbelower.ThewaystorealizecolorlessONUandupstreamtransmissionare:useoftunablelasersTheONUconfigurationandsystemconfigurationare:WDMInthiskindofconstruction,thelightisattheONUandthebitrateisaboutlOGbs.spectrumslicingofbroadbandlightsourceTheONUconfiguration:

四DMBLSRx四DMBLSRxThelightsourceisattheONUandthebitrateisabout1.25Gbps.3)erasethedatacontentonthereceiveddownstreamcarrierandre-modulateitwiththeupstreamdataatONU(wavelengthre-use)TheONUconfigurationandsystemconfigurationare：ThelightsourceisattheOLTandthebitrateisaboutlOGbps.self-seedingorinjectionseedingofreflectiveSOA(RSOA)atONUTheONUconfigurationandsystemconfigurationare:thelightsourceisattheONUandthebitrateisabout1.25Gbps.injectionlockingoftheFabryPerotlaseratONUThesystemconfigurationis:carrierdistributedfromOLTThesystemconfigurationis:『Fabry-Pcratla自芯(Huactnnlockini『Fabry-Pcratla自芯(HuactnnlockiniLaserinjectionandBLSinjectionlocking?Laserinjection:BLSinjectionlocking:

RayleighBackscatteringMitigationWDM-PONS?ElectricalElectricalfilteringandline-codIng（减轻）inSingle-FeederEqualization)Frequencydltl^eringiofthelightsourcetorndjRlightr：c>herftrti£ie（减轻）inSingle-FeederEqualization)Rayleighbackscatteringisthefundamentallossofopticalfiber,whichiscausedbytheindexfluctuation.Rayleighbackscatteringflowsinbackwarddirection.Whensinglefiberisusedforbidirectionaltransmission,thisintrinsiccrosstalkseverelydegradessystemperformance.TherearetwomainmeanstosuppressRayleighbackscattering.Oneiselectricalwayandtheotherisopticalway.FromtheElectricaldomain:Use8B10Blinecodingandelectricalfiltering.Thiscanresult12dBimprovementonreceiversensitivity(SCR=18dB).UseelectricalEqualization.Thiscanresult2dBimprovementonreceiversensitivity(SCR=20dB).FromtheOpticaldomain：UseSCM(subcarriermodulation)andopticalbandpassfiltering.Thiscanresult1.9-dBpenaltyaftertransmission.ApplingopticalnotchfilteringusingDI.Temperaturecontrolisneededwhenusingthisway.0.3-dBpenaltyaftertransmission(DPSKwithdifferentmodulationdepths)canbegot.Besides,wecanalsousephasemodulation,Carriersuppressedsubcarrieramplitudemodulatedphaseshiftkeying(CSS-AMPSK)format,CarrierSuppressedSingleSidebandformat,subcarriermodulationetc.atONUtomitigateRayleighscattering.PhaseModulationatONU^Carriersuppressedsubcarrier-amplitudemodulatedphaseshiftkeying(CSS-AMPSK)format$UseofCarrierSuppressedSingleSidebandformatatONUgUseofsubcarriermodulationatONU@UseofDPSKasupstreamsignalformat(245-250)FaultmaintenanceusingOTDR?Ifthelightpulsetravelsthroughasplice,bend,orconnection；lightwillbelostandthepulsediminished.•Ifthespliceorbreakis「Mlect%电thentheOTDRtracewillshowapeakabovethebackscatterradiation.O.cdB-fi.O■lO.Ci-1S.0-200靖"-300FtwrEnd也降CowectofO.cdB-fi.O■lO.Ci-1S.0-200靖"-300FtwrEnd也降CowectofPaiiF,例ConneetcrFu&iQfL05Q10由15,QEQ,O25.030.0叩i3S.0SampteOTDRVacoOpticalbroadcast/multicastoverlayonPONsusingdifferentmodulationformat?OpticalBroadcastQone-to-alllightpathsareestablishedontheopticallayerqTDM-PONisinherentlyabroadcastnetwork,WDM-PONisnot.OpticalMulticastQone-to-many(subset)lightpathsareestablishedontheopticallayerflightpathscanbeflexiblyreconfiguredOpticalPowerSplitting^relativelymoreefficientthancopyingpacketsattheIPlayer^requiresmulticastroutingandwavelengthassignment.©suffersfrompower-budgetconstraintsandincreasednetworkcomplexity.OpticalMulticastOverlay^multicasttrafficisoverlaidontotheexistingpoint-to-pointwavelengthchannelsusingvariousfeasibleandpracticalopticalsignalprocessingtechniques.QtheexistingaccessnetworkinfrastructurecanbegracefullyupgradedtosupportthemulticasttrafficOpticalMulticastOverlayonWDM-PONsDesignissues:Qhowtoaddoroverlaythemulticasttraffictotheexistingnetworkinfrastructurewh