文档介绍：´-JeanEssiambreBellLaboratories,Alcatel-Lucent,Holmdel,NJ,,high-speedopticaltransmissionsystemshaveincreasinglybeenbuildingontechniquesthatarewellestablishedinradio-frequency(municationsystems,,linecoding,enhancedforwarderrorcorrection(FEC),-Gb/srealmisdrivenbythedesiretosteadilylowerthecostperend-to--freereachofopticallinesystemsatthehighestpossibleper-fibertransmissioncapacities,--ingestablishedmethodsfromopticalphysicstoincreasetransmissionreach,systemcapacity,,municationtechniquesfallintotwomainareas,distinguishedbytheper-wavelengthsymbolratestheyoperateat:•Atper-channelsymbolratesof10Gbaud,electronicsignalprocessingran-gingfromsimplefeed-forwardanddecision-feedbackequalizers(FFE,DFE)atthereceiverallthewaytomaximum-likelihoodsequenceestimation(MLSE)merciallyavailabletoday[13],mercial10-Gb/stransportproducts[4,5].Digitalsignalpredistortionatthetransmitterisbeingactivelypursued[6],municationsVB:worksCopyrightÓ2008,:´-JeanEssiambreexperiencingrenewed1interest[1416].Incontrasttowidelydeployeddirectdetection,coherentdetectionallowselectronicsignalprocessingtomakeuseofthefullopticalfield(magnitudeandphase),whichcanbeexploitedformoreefficientmitigationoffibertransmissionimpairmentssuchaschromaticdis-persion(CD)orpolarizationmodedispersion(PMD).Coherentdetectionresearchisalsoaimingatincreasingthebitratethroughmultilevelmodulationandpolarizationmultiplexingwhilekeepingthesignalbandwidthsimilartothatofa10-Gb/sbinarysignaltoreuse10-Gb/sopticallineinfrastructureandtoincreasethesystem’