《光通信技术》课件：Lecture9

Chapter14

Fiber-OpticNetworks:anintroductionX.WuDepartmentofOpticalEngineering“What”and“How”ofdatatransmissionWhattotransmit:Voice,VideoandDataVoiceistransmittedbytelecommunicationsnetworks:astreamofbitsVideoistransmittedthrucableTVnetworks:broad-bandwidthconnectionsDataistransmittedbycomputernetworks:telephoneorCATVcompanyservicesTheintegrationoftechnologiesandservicesisthemainfeatureofmoderncommunicationsDepartmentofOpticalEngineeringTelephoneNetworksAccessnetwork:allconnectionsfromcustomerpremisesalongwithlocalswitchesTransportnetwork:Allinterofficelinks,allregionalandlong-distanceconnectionsalongwithswitchesDividedintothreesectionsbylinerates:AccessMetroLong-haul(core)DepartmentofOpticalEngineeringAccessandTransportNetworkDepartmentofOpticalEngineeringTelephone/AccessNetworksBasedontraditionaltwisted-paircopperwire4kHzbandwidthassignedtoanindividualvoicechannel18kilofeetor5.48kmEffortsundertakentowidenthisbottleneckbutnotreplacecopperwirew/fiber:advancedmodulationandencodingtechnologyISDN(integratedServicesDigitalNetwork144Kbit/sB-ISDN(broadbandISDN)620Mbit/sxDSL(xdigitalsubscriberline,x=A,H,V,U..):ADSL:6Mbit/sx=asymmetricVDSL:20Mbit/sx=veryhighspeedDepartmentofOpticalEngineeringT-1TransmissionSystemEachSample:8bitSampling24Voicechannels:8bits/samplex24samples/frame+1bit/frame(delimitframeboundary)=193bits/frame193bits/framex8000frames/s=1.544Mbits/s

DepartmentofOpticalEngineeringTcarriersystemandETDMsystemTsystem:NorthAmericaandJapanETDM:EuropeandotherpartsintheworldServicebitsforpacking,transport,sync.User’sdata:PayloadDepartmentofOpticalEngineeringDifferencebetweenTandEtransmissionsystemsDifference:TransmissioncharacteristicsSynchronization:DS(T)signalsuseAMIlinecoding,using8ormorezeroforareceivertosyncw/transmitter’sclock,thesynislostwhennodatasent.Esystemalsousesbipolarcoding,buthasdifferentvoltages,pulseshapes…,using3zeroforsyncFraming……DepartmentofOpticalEngineeringSynchronousOpticalNetwork(SONET)SONET:asetofstandardsdevelopedbyBellcore(TelcordiaTechnology),thenlateradoptedbyITU-T(telecommunicationstandarizationsectorofint’lcommunicationunion):anint’lstandarddesignatedsynchronousdigitalhierarchy(SDH)SONET:aTDMsystemprovidingsynchronoustransmission,specifiestherates,formats,andparametersofallphysicaltransmissionmediaStartingandendingbitsareaddedtoeachcellofdatatransmittedClocksyncisamajorconcern

DepartmentofOpticalEngineeringSONET/SDHmultiplexingSONET:supportsbothelectricalandopticaltransmission;STS-N(synchronoustransportsignals)andOC-N(opticalcarrier)e.g.STS-3OC-3STM-1:155.52Mbit/sEachchannel(8bits)isassignedanindividualtimeslotwithinoneframeDepartmentofOpticalEngineeringSTSformatFramesize:9rowsx90columesof8-bitbytes=810bytesor6480bitsDurationofeachframe125sIncluding:PayloadOverheadPathoverheadTransportoverheadSync.PayloadenvelopeDepartmentofOpticalEngineeringSTSTransmissionSPEisaninformationsignal,called“tributary”withinSTS-1PayloadismultiplexedintoSPEApathloadisinsertedintotheSPEbyendtransmitter,attacheduntilunpackedbyendreceiverForsignalswhosebitrateislowerthanSTS-1,SONETsubdividesanSPEintosmallerenvelopes:virtualtributaries(VT)OC-482488.32Mbit/sor2.5Gbit/s;OC-19210Gbit/s,OC-76840Gbit/s……DepartmentofOpticalEngineeringTDMv.s.WDMTotransmit100Gbit/soverafiber:100wavelengthchannelsx10Gbit/s10wavelengthchannelsx100Gbit/s100Gbit/shasbeenachieved(1997)RZprovidesatime-guardzonebetweenpulsesfor>40Gbit/stransmissionFiberDelaylinesDepartmentofOpticalEngineeringComputerNetworksLAN,MAN,WANLANsaretreatedinthesamewayregardlessofwhetherornottheyuseopticalfiber.MAN:metropolitanareanetwork,linkingmanyLANswithinametropolitanareaWAN:wide(world)areanetwork:linkallcomputersintheworldNotahierarchicalstructure:donothavetogothruLANfirst,thenMAN,andfinallyWAN(专网！）DepartmentofOpticalEngineeringTwoProtocols:ATMandIPATM(asynchronoustransfermode)Connection-orientedtransmissionsystem,apathforthecellmustbeestablishedbeforethetransmissionstarts(asynchronous:timetosetupaconnectionisnotpredetermined)ATMpacket:afixedlengthcellcontaining53bytes,including48-bytepayloadanda5-byteheader(overhead)AdvantagesIntegration:cancarryanytypeofinfo:voice,data,video…SupportbothcircuitandpacketswitchingSupportstransmissiononanyscalefromLANstoWANswithoutadditionaltransformationofsignalProvidesQuality-of-serviceguaranteesuchasthroughput,BW,delay,anderrorcontrolDepartmentofOpticalEngineeringTwoprotocols:ATMandIPIP(internetprotocol)orTCP/IPwhenusedwithTCP(transmissioncontrolprotocol)A“connectionless”transmissionsystemIPpackets:theentiremessageisdividedintopacketsandtransmittedthrunetworktotheirdestinationasindependentunitsPacketlengthvariesandtransmissionroutenotspecifiedMainadvantage:canworkwithnearlyallexistingtransmissionsystems:IP/ATM,voiceoverIP…DepartmentofOpticalEngineeringElementsoftheArchitectureofFiber-OpticNetworksPreviousdiscussion-thekindofinfoneededtotransmitNow:howarenetworksorganized?NetworkarchitecturePhysicalmedia(ourfocussofar)LogicalentitiesCar:localstreets-regionalfreeways-highwaysMessage:local-regional-globalphysicalnetworksCar:trafficrulesMessage:specificrulescontrolitstransmissionDepartmentofOpticalEngineeringTrafficrules:protocolsProtocol:asetofrulesthatprovidescommunicationbetweenthesourceandthedestinationpoint.PreventcollisionRegulatestheform….Services:asetofoperationsorstepsthathastobeputintoeffectifcommunicationistobesuccessful.Nottiedtoprotocolphysically,Independentofprotocol,canbeupdatedDepartmentofOpticalEngineeringLogicalarchitectureofanOSI(Opensysteminterconnection)Network:acollectionofnodesconnectedbylinksLinks:transmissionmediaNodes:intelligentworkformessagetransmissionLogical(notphysical)structureDepartmentofOpticalEngineeringFunctionoflayerLayer1:transmissionofbitsLayer2:takingdatafromlayer3andaddingheaderandtailertomakeframe,Layer3:takingdatafromlayer4andaddingroutinganderror-controlinfoLayer4:acceptinginfofromlayer5anddivides/resemblesthedataintopacketsLayer5:responsibleforlog-inandlog-out,timeofconnectionLayer6:presentsthedataintheproperformat,convertsdataintoaudio,video,ordataDepartmentofOpticalEngineeringVirtualCommunicationVirtualcommunication:theinterchangebetweenthesamelayersatthetransmittingandreceivingnodes,whileactualcommunicationoccursthroughbitstransmittedbythephysicallayerNetworklayer3:maintainingvirtualcommunicationbetweenthesourceandthedestination,anend-to-endlayerTransportlayer4:responsibleforeffectingend-to-endcommunication,atrulyend-to-endlayerDepartmentofOpticalEngineeringPDUandIDUPDU(protocoldataunit):tellthereceivinglayerwhattodoIDU(interfacedataunit):performserviceforthelayerdirectlyabovePDU:CarriesinfoaboutthefunctionsofaspecificlayerAddedbeforepassingdatadowntothenextlayerThemeansforvirtualcommunication-sameleveledlayercomm.IDU:CarriesinfoabouttheserviceseachlayerprovidesInfounitthateachlayeraddsbeforepassingdatatothelayeraboveCommunicationbetweentopandbottomlayersatthesamenodeDepartmentofOpticalEngineeringOSIProtocolsProtocols:setofrulesimplementedassoftwareprogramsDevelopedandstandardizedGovernmentOSIprotocol(GOSIP)GMandBoeing:MAP/TOP-manufacturingautomationprotocol/technicalofficeprotocolTCP/IP:TCPatlayer4andIPatlayer3DepartmentofOpticalEngineeringElementsofaSONET/SDHnetworkSONET:developedforhigh-speedtelephonenets,Gen.1opticalnetDigitalcross-connectTerminalmultiplexerOC-3/OC-12OC-12/48/192DepartmentofOpticalEngineeringSONETLayersSONETsubdivisionlongreach(LR)OC-481550nmDFBIntermediatereach(IR)Shortreach(SR)OC-31310nmLEDLayersassociatedwithnodes:Physical:transmissionSection:addinghead,errormonitoringandcontrol,sendingdatatophysicallayerLine:multiplexing,neededatADM,TM,Path:connectionbetweensourceanddestinationDatalinklayerinOSINetworkinglayerinOSIDepartmentofOpticalEngineeringIP,ATMandSONETnetworksATM->SONET:connectingATMswitchestoSONETadaptercards,convertingATMcellsintoSTSframesIP->ATM:connectingIProuterstoATMnetwork,IPpacketsconvertedintoATMcellsDepartmentofOpticalEngineeringReceiverPartsofReceivermodulePhotodiodeCouplingopticsPreampQuantizerFilterAmp/limiterDecisioncircuitClockrecoveryPhotodiodePINSiliconandInGaAsWideBWFront-illuminatedandrear-illuminated