光纤通信简介专业英语

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1、OpticalFiberCommunication-introductionForewordTheuseoflighttosendmessagesisnotnew.Fireswereusedforsignalinginbiblicaltimes,smokesignalshavebeenusedforthousandsofyearsandflashinglightshavebeenusedtocommunicatebetweenwarshipsatseasincethedaysofLordNelson.Theideao

2、fusingglassfibertocarryanopticalcommunicationsignaloriginatedwithAlexanderGrahamBell.Howeverthisideahadtowaitsome80yearsforbetterglassesandlow-costelectronicsforittobecomeusefulinpracticalsituations.Thepredominantuseofopticaltechnologyisfortransmissionofdataath

3、ighspeed.Opticalfibersreplaceelectricwireincommunicationssystemsandnothingmuchelsechanges.Perhapsthisisnotquitefair.Theveryspeedandqualityofopticalcommunicationssystemshasitselfpredicatedthedevelopmentofanewtypeofelectroniccommunicationsitselfdesignedtoberunono

4、pticalconnections.ATM(AsynchronousTransferMode)andSDH(SynchronousDigitalHierarchy)technologiesaregoodexamplesofthenewtypeofsystems.Itisimportanttorealizethatopticalcommunicationsisnotlikeelectroniccommunications.Whileitseemsthatlighttravelsinafibermuchlikeelect

5、ricitydoesinawirethisisverymisleading.Lightisanelectromagneticwaveandopticalfiberisawaveguide.Everythingtodowithtransportofthesignaleventosimplethingslikecoupling(joining)twofibersintooneisverydifferentfromwhathappensintheelectronicworld.Thetwofields(electronic

6、sandoptics)whilecloselyrelatedemploydifferentprinciplesindifferentways.Somepeoplelookaheadto“true”opticalnetworks.Thesewillbenetworkswhereroutingisdoneopticallyfromoneend-usertoanotherwithoutthesignaleverbecomingelectronic.Indeedsomeexperimentallocalarea(LAN)an

7、dmetropolitanarea(MAN)networkslikethishavebeenbuilt.In1998opticallyroutednodalwideareanetworksareimminentlyfeasibleandthenecessarycomponentstobuildthemareavailable.However,nosuchnetworkshavebeendeployedoperationallyyet.In1998the“happening”areainopticalcommunica

8、tionswasWavelengthDivisionMultiplexing(WDM).Thisistheabilitytosendmany(perhapsupto1000)independentopticalchannelsonasinglefiber.ThefirstfullycommercialWDMproductsappearedont