2025/12/20《電子信息與通信工程專業(yè)英語》機械工業(yè)出版社

Chapter4

ElectromagneticFieldandWave

Outline4.1ElectromagneticFieldsTheory

4.2DevelopmentofMobileCommunications4.3OpticalFiberCommunication2025/12/20《電子信息與通信工程專業(yè)英語》機械工業(yè)出版社4.3OpticalFiberCommunicationOutlineApplicationsHistoryOpticalFiberOpticalFiberSystemAdvantagesOfOpticalFiber20十二月2025電子信息與通信工程專業(yè)英語TerminologyInformationAge

n.信息時代attenuationn.衰減interferencen.干擾、干涉Photophonen.光線電話機pulse-spreadingn.脈沖擴展dispersion-shiftedfibersn.色散位移光纖longitudinalmoden.縱模opticalamplificationn.光放大wavelength-divisionmultiplexing（WDM）

n.波分復(fù)用datacapacityn.信息容量nonlineareffectsn.非線性效應(yīng)totalinternalreflectionn.全內(nèi)反射20十二月2025電子信息與通信工程專業(yè)英語refractiveindexn.折射率indexprofilen.折射率曲線numericalaperturen.數(shù)值孔徑cabletelevisionn.有線電視laserdioden.激光二極管incoherentlightn.非相干光coherentlightn.相干光electroluminescencen.場致發(fā)光launchedpowern.發(fā)射功率erbiumdopedsilicafibersn.摻鉺石英光纖20十二月2025電子信息與通信工程專業(yè)英語Opticalfiberisusedbymanytelecommunicationscompaniestotransmittelephonesignals,Internetcommunication,andcabletelevisionsignals.Duetomuchlowerattenuationandinterference,opticalfiberhaslargeadvantagesoverexistingcopperwireinlong-distanceandhigh-demandapplications.However,infrastructuredevelopmentwithincitieswasrelativelydifficultandtime-consuming,andfiber-opticsystemswerecomplexandexpensivetoinstallandoperate.Duetothesedifficulties,fiber-opticcommunicationsystemshaveprimarilybeeninstalledinlong-distanceapplications,wheretheycanbeusedtotheirfulltransmissioncapacity,offsettingtheincreasedcost.Applications20十二月2025電子信息與通信工程專業(yè)英語Todaymorethan80percentoftheworld'slong-distancetrafficiscarriedoveroptical-fibercables.Telecommunicationsapplicationsoffiber-opticcablearewidespread,rangingfromglobalnetworkstodesktopcomputers.Theseinvolvethetransmissionofvoice,data,andvideooverdistancesoflessthanametertohundredsofkilometers.Carriersuseopticalfibertocarryanalogphoneservice.Cabletelevisioncompaniesalsousefiberfordeliveryofdigitalvideoservices.Intelligenttransportationsystemsandbiomedicalsystemsalsousefiber-optictransmissionsystems.Opticalcableisalsotheindustrystandardforsubterraneanandsubmarinetransmissionsystems.20十二月2025電子信息與通信工程專業(yè)英語

HistoryOpticalfiberwassuccessfullydevelopedin1970byCorningGlassWorks,withattenuationlowenoughforcommunicationpurposes(about20dB/km).Thefocusofdevelopmentforthefifthgenerationoffiber-opticcommunicationsisonextendingthewavelengthrangeoverwhichaWDMsystemcanoperate.Theconventionalwavelengthwindow,knownastheCband,coversthewavelengthrange1.53-1.57

μm,anddryfiberhasalow-losswindowpromisinganextensionofthatrangeto1.30-1.65

μm.Otherdevelopmentsincludetheconceptof"opticalsolitons"，pulsesthatpreservetheirshapebycounteractingtheeffectsofdispersionwiththenonlineareffectsofthefiberbyusingpulsesofaspecificshape.20十二月2025電子信息與通信工程專業(yè)英語OpticalFiberTypicalopticalfibersarecomposedofcore,claddingandbuffercoating.Thecoreistheinnerpartofthefiber,whichguideslight.Thecladdingsurroundsthecorecompletely.20十二月2025電子信息與通信工程專業(yè)英語Opticalfibersarebasedentirelyontheprincipleoftotalinternalreflection.Therefractiveindexofthecoreishigherthanthatofthecladding.Solightinthecorethatstrikestheboundarywiththecladdingatananglelargerthancriticalanglewillbereflectedbackintothecorebytotalinternalreflection.Fig.4-11illustratestheoperationalprincipleofopticalfiber.20十二月2025電子信息與通信工程專業(yè)英語Twomaintypesofopticalfiberusedinopticcommunicationsincludemulti-modeopticalfibersandsingle-modeopticalfibers.Fibersthatcarrymorethanonemodeataspecificlightwavelengtharecalledmultimodefibers.Indexprofileistherefractiveindexdistributionacrossthecoreandthecladdingofafiber.Someopticalfiberhasastepindexprofile,inwhichthecorehasoneuniformlydistributedindexandthecladdinghasaloweruniformlydistributedindex.Otheropticalfiberhasagradedindexprofile,inwhichrefractiveindexvariesgraduallyasafunctionofradialdistancefromthefibercenter.Fig.4-13showssomecommontypesofindexprofilesforsinglemodeandmultimodefibers.2025/12/20《電子信息與通信工程專業(yè)英語》機械工業(yè)出版社2025/12/20《電子信息與通信工程專業(yè)英語》機械工業(yè)出版社20十二月2025電子信息與通信工程專業(yè)英語OpticalFiberSystemModernfiber-opticcommunicationsystemsgenerallyincludeanopticaltransmittertoconvertanelectricalsignalintoanopticalsignaltosendintotheopticalfiber,acablecontainingbundlesofmultipleopticalfibersthatisroutedthroughundergroundconduitsandbuildings,multiplekindsofamplifiers,andanopticalreceivertorecoverthesignalasanelectrical