通信与电子信息专业英语 课件 Unit 9 Optical Communication

Unit9OpticalCommunication9.1OpticalCommunicationSystems

9.2PassiveOpticalNetworks9.1OpticalCommunicationSystemsWordsandExpressionsBackgroundsTextWordsandExpressionswaveguide n.波导aclassofdevicesthatconfinesanddirectsthepropagationofelectromagneticwaves.typicalexamplesincludehollowmetallictubes,coaxialcables,andopticalfibres.WordsandExpressions5accommodate v.容纳；为…提供空间；

顺应，适应（新情况）Becausethefrequencyoflightisextremelyhigh,itcanaccommodateveryhighratesofdatatransmissionwithexcellentreliability.由于光的频率非常高，因此光通信可以提供非常高的数据传输速率，并具有出色的可靠性。WordsandExpressions6photodetector n.光电探测器；光检测器photodiode 光电二极管phototransistor 光电三极管Photodiodesaredesignedtodetectphotonsandcanbeusedincircuitstosenselight.Phototransistorsarephotodiodeswithsomeinternalamplification.WordsandExpressions7LASER:LightAmplificationbyStimulatedEmissionofRadiation

n.激光；激光器laserprinter 激光打印机monochromatic

adj.单色的；单色光的；

单频的；单能的polychromatic 多色的monochromaticsource

单色光源WordsandExpressions8coherent adj.相干的；连贯的； 一致的；合乎逻辑的incoherent

非相干的，不连贯的coherentopticalcommunication 相干光通信insync(synchronization) 同步；一致；协调intensitymodulation 强度调制WordsandExpressions9NRZ:Non-ReturntoZero 不归零的；不归零制OOK:On-OffKeying 开关键控；通断键控DigitalmodulationisusuallyNRZ-formattedbinarydatathatturnsalaserofforontoproduceoff-onkeying(OOK)oramplitude-shiftkeying(ASK).WordsandExpressions10attenuation n.衰减；变薄；稀释echoattenuation

回声衰减

attenuationcoefficient(dB/km) 衰减系数Communicationbylightbeaminfreespaceisimpracticaloververylongdistancesbecauseofthegreatattenuationofthelightduetoatmosphericeffects.在自由空间中通过光束进行长距离通信是不切实际的，因为大气效应会导致光的大幅衰减。WordsandExpressions11reflect v.反射(声、光、热等)；反映；认真思考refract v.使(光线)折射；使产生折射disperse v.散射；分散；驱散；疏散；传播WordsandExpressions12obliterate v.毁掉；覆盖；清除Artificiallightbeamsusedtocarryinformationareobliteratedduringdaylighthoursbythesun.用于携带信息的人造光束在白天被太阳光覆盖。refine v.改进；改善；精炼；提纯；去除杂质purify,filter,improve,enhancerefineonamethod

改进方法immense adj. 极大的；巨大的WordsandExpressions13photocell

n.光电池；光电管；光电元件Photoelectriccell,alsocalledElectricEye,Photocell,orPhototube,anelectrontubewithaphotosensitivecathodethatemitselectronswhenilluminatedandananodeforcollectingtheemittedelectrons.WordsandExpressions14repeater

n.网络中继器；转发器；无线中继O/ERepeater

光电转换型中继器AORepeater

全光型中继器relaystation 中继站backbone

n.骨干；网络骨干；主干网distributedbackbone

分布式主干网shipboardcommunication

船上通信Background15FiberOpticCommunications,PurdueUniversityhttps:///course/fiber-optic-communicationsTextOutline16IntroductionLightWaveCommunicationinFreeSpaceFiber-OpticCommunicationSystemApplicationsofFiberOpticsIntroduction17Opticalcommunicationsystemsuselighttotransmitinformationfromoneplacetoanother.Thetransmissionmediumiseitherfreespaceaswithradiowavesoraspeciallight-carryingcableorwaveguideknownasfiber-opticcable.LightWaveCommunicationinFreeSpace18It(anopticalcommunicationsystemusingfreespace)consistsofalightsourcemodulatedbythesignaltobetransmitted,amodulator,aphotodetectortopickupthelightandconvertitbackintoanelectricsignal,anamplifier,anda

demodulatortorecovertheoriginalinformationsignal.LightWaveCommunicationinFreeSpace19Lasersgeneratemonochromatic,orsingle-frequency,lightthatisfullycoherent;i.e.,allthelightwavesarelinedupinsyncwithoneanotherandasaresultproduceaverynarrowandintenselightbeam.激光产生完全相干的单色或单频光，即所有光波彼此同步排列，产生高强度的窄光束。LightWaveCommunicationinFreeSpace20ModulatorAnalogsignalsvarythebrightnesscontinuouslyoveraspecifiedrange.Digitalsignalssimplyturnthelightbeamoffandonatthedatarate.Asimplelighttransmitterwithseriesamplitudemodulator.Analogsignals:Transistorvariesitsconductionandactsasavariableresistance.Pulsesignals:Transistoractsasasaturatedon/offswitch.21Astheanalogsignalgoespositive,thebasedriveonthetransistorincreases,turningthetransistoronharderanddecreasingitscollector-to-emittervoltage.Thisappliesmoreofthesupplyvoltagetothelightsource,makingitbrighter.当模拟信号变为正时，晶体管上的基极电压增大，使晶体管导通，降低了集电极到发射极间的电压。这会导致电源施加在光源上的电压变大，从而使其更亮。LightWaveCommunicationinFreeSpace22Frequencymodulationisnotusedinlightcommunication.Thereisnopracticalwaytovarythefrequencyofthelightsource,evenamonochromaticsourcesuchasanLEDoralaser.Pulsemodulationreferstoturningthelightsourceoffandoninaccordancewithsomeserialbinarysignal.LightWaveCommunicationinFreeSpace23Fog,haze,smog,rain,snow,andotherconditionsabsorb,reflect,refract,anddispersethelight,greatlyattenuatingitandtherebylimitingthetransmissiondistance.雾、霾、烟雾、雨、雪和其他条件会吸收、反射、折射和散射光线，大大衰减光强，从而限制传输距离。LightWaveCommunicationinFreeSpaceFiber-OpticCommunicationSystem24Insteadoffreespace,sometypeoflight-carryingcablecanbeused.Itsgreatadvantageisitsimmenseinformation-carryingcapacity(widebandwidth).Whenmultiplexingtechniquessimilartothoseintelephoneandradiosystemsareused,fiber-opticcommunicationsystemshaveanalmostlimitlesscapacityforinformationtransfer.Fiber-OpticCommunicationSystem25Thecomponentsofatypicalfiber-opticcommunicationsystem:lightsourcetransmitteropticalfiberreceiverCODECFiber-OpticCommunicationSystem26Sincethelightisgreatlyattenuatedwhenittravelsoverlongrunsofcable,atsomepointitmaybetooweaktobereceivedreliably.Toovercomethisproblem,specialrelaystationsareusedtopickupthelightbeam,convertittoelectricalpulsesthatareamplified,andthenretransmitonanotherlightbeam.ApplicationsofFiberOptics27Fiber-opticnetworksalsoformthecoreorbackboneoftheInternet.Fiber-opticcablesarenomoreexpensiveorcomplextoinstallthanstandardelectricalcables,yettheirinformation-carryingcapacityismanytimesgreater.光缆的安装并不比标准电缆更昂贵或更复杂，但其信息承载能力要强很多倍。ApplicationsofFiberOptics281.TVstudiototransmitterinterconnectioneliminationamicrowaveradiolink9.Nuclearplantinstrumentation.

2.Closed-circuitTVsystemsusedinbuildingsforsecurity.10.Collegecampuscommunication.3.Securecommunicationsystemsatmilitarybases.11.Utilities(electric,gas,andsoon)stationcommunication.4.Computernetworks,widearea,metroandlocalarea.12.CableTVsystems,replacingcoaxialcable.13.TheInternet5.Shipboardcommunication.14.Backhaulforcellularbasestations.6.Aircraftcommunication/controls.15.Distributedantennasystems(DAS).7.Interconnectionofmeasuringandmonitoringinstrumentsinplantsandlaboratories.16.Connectionsbetweenservers,routers,andswitchesindatacenters.8.Dataacquisitionandcontrolsignalcommunicationinindustrialprocesscontrolsystems.17.Connectionbetweenthecellularbasestationandtheremoteradioheadmountedattheantenna.9.2PassiveOpticalNetworksWordsandExpressionsBackgroundsText29WordsandExpressionsMAN:Metropolitan-AreaNetwork城域网SAN:Storage-AreaNetwork存储区域网Astorageareanetwork(SAN)isadedicatedhigh-speednetworkorsubnetworkthatinterconnectsandpresentssharedpoolsofstoragedevicestomultipleservers.WordsandExpressions31transceiver n.无线电收发机；收发器Atransceiver(TRX)isaacombinationoftransmitter(Tx)/receiver(Rx)inanonlypackage.RFTransceiver Fiber-opticTransceiver EthernetTransceiver WirelessTransceiverWordsandExpressions32nuisance

n.麻烦事；讨厌的人（或东西）；损害TheseOEO(optical-to-electricalandelectrical-to-optical)repeatersandamplifiersareanuisanceaswellasexpensiveandpower-hungry.power-hungry 能量短缺powershortage,powersupply,powerconsumption,powergridintervening adj.介于中间的；发生于其间的WordsandExpressions33splitter n.光分路器；分光器combiner n.合路器；合波器；合成器；复合器；组合器WordsandExpressions34DSL:DigitalSubscriberLoop 数字用户环路ADSL:AsymmetricDSL 非对称数字用户环路distribution n.分布；分配；分发distributedcomputing 分布式计算centralized/decentralized 集中式/分散式WordsandExpressions35ATM:AsynchronousTransferMode 异步传输模式ATMisahigh-speed,broadbandtransmissiondatacommunicationtechnologybasedonpacketswitching,usingbandwidthatmaximumefficiencywhilemaintainingaguaranteedQoS.ATM是一种基于分组交换的高速、宽带传输数据通信技术，它在保证服务质量的同时以最大效率使用带宽。WordsandExpressions36BPON:BroadbandPassiveOpticalNetwork宽带无源光网络GPON:GigabitPON吉比特无源光网络；千兆无源光网络encapsulation n.封装；封闭；胶囊化作用；包封dataencapsulation

数据内嵌encapsulationtechnology封装工艺encapsulate/decapsulate封装/解封装protocol-agnostic 协议无关WordsandExpressions37SONET:SynchronousOpticalNetwork 同步光纤网络；

同步光网络SDH:SynchronousDigitalHierarchy 同步数字体系SONET/SDHwasoriginallystandardizedforconnectingonefibersystemtoanotherattheopticallevel,toformasingleinternationalstandardforfiberinterconnectsbetweentelephonenetworksofdifferentcountries.WordsandExpressions38CO:CentralOffice 电话总局；网络中心局；端局ISP:InternetServiceProvider 互联网服务供应商ICP:InternetContentProvider 互联网内容供应商telephonecarrier

电信运营商mobilecarrier 移动运营商telcomoperators 电信运营商networkoperator 网络运营商VoIP:VoiceoverIP IP电话；网络电话WordsandExpressions39OLT:OpticalLineTerminal

光线路终端ONT:OpticalNetworkingTerminal

光网络终端EPON:EthernetPassiveOpticalNetwork 以太网无源光网络defacto adj.事实上；事实上的；实际上的Background40OpticalEngineering,UniversityofColoradoBoulderhttps:///specializations/optical-engineeringTextOutline41IntroductionThePONConceptPONTechnologiesIntroduction42Passiveopticalnetwork(PON)isatypeofmetropolitanareanetworktechnology.ThistechnologyisalsoreferredtoasFTTH.Similartermsare:FTTP:FiberToThePremisesFTTH:FiberToTheHomeFTTB:FiberToTheBuildingFTTC:FiberToTheCurbFTTCab:Fibre-to-the-CabinetThePONConcept43ThetermpassiveimpliesnoOEOrepeaters,amplifiers,oranyotherdevicethatusespower.Instead,thetransmittersendsthesignaloutoverthenetworkcable,andareceiveratthedestinationpicksitup.Therearenointerveningrepeatersoramplifiers.Onlypassiveopticaldevicessuchassplittersandcombinersareused.ThePONConcept44Byusinglow-attenuationfiber-opticcables,powerfullasers,andsensitivereceivers,itispossibletoachievedistancesofuptoabout20kmwithoutinterveningactiveequipment.ThismakesPONsidealformetropolitan-areanetworks.通过使用低损耗光纤、高能激光器和灵敏的接收器，可以在不使用有源设备的情况下达到约20公里的传播距离。这使得无源光网络（PON）成为城域网的理想选择。ThePONConcept45PONswillbecompetitivewithcableTVandDSLconnectionsbutfasterthanboth.Usingopticaltechniques,theconsumercanhaveanInternetconnectionspeedof100Mbpsto1Gbpsorhigher.AndPONsmakedigitalTVdistributionmorepractical.Furthermore,theyprovidetheextrabandwidthtocarryInternetphonecalls(VoIP).PONTechnologies46ThereareseveraldifferenttypesofPONsandstandards:APON:usingATMBPONEPONGPONXGPON/10G-PONPONTechnologies47Thecarriercentraloffice(CO)servesastheInternetserviceprovider(ISP),TVsupplierortelephonecarrierasthecasemaybe.Apassiveopticalnetwork(PON)usedasahigh-speedInternetconnectionandforTVdistributioninfibertothehomesystems.PONTechnologies48Theequipmentatthecarriercentraloffice(CO)isreferredtoastheopticallineterminal(OLT).Apassiveopticalnetwork(PON)usedasahigh-speedInternetconnectionandforTVdistributioninfibertothehomesystems.PONTechnologies49Asignalon1490nmcarriesallInternetdataandanyvoicesignals,1550nmforTV.Theyaremixedoraddedinapassivecombinertocreateacoarsewavelengthdivisionmultiplexed(CWDM)signal.Apassiveopticalnetwork(PON)usedasahigh-speedInternetconnectionandforTVdistributioninfibertothehomesystems.PONTechnologies50Additionalsplittersareusedalongthewaytofurthersplitthesignalsfordistributiontomultiplehomes.Justrememberthateachtimethesignalissplit,itspowerisdecreasedbythesplitratio.Apassiveopticalnetwork(PON)usedasahigh-speedInternetconnectionandforTVdistributioninfibertothehomesystems.PONTechnologies51Atthereceivingend,eachsubscriberhasanopticalnetworkingunit(ONU)oropticalnetworkingterminal(ONT).TheseboxesconnecttoyourPC,TVset,and/orVoIPtelephone.Apassiveopticalnetwork(PON)usedasahigh-speedInternetconnectionandforTVdistributioninfibertothehomesystems.PONTechnologies52It(10G-PON)canachieve10Gbpsdownstreamon1577nmand2.5Gbpsupstreamon1270nm.ThesedifferentwavelengthsallowittocoexistwithexistingGPONservices.它(10G-PON)的下载带宽达到10Gbps，波长采用1577nm，上传带宽达到2.5Gbps，波长采用1270nm。使用不同的波长允许它与现有的GPON服务共存。PONTechnologies53AnotherwidelyusedstandardisEPON,orEthernetPON.WhileBPONandGPONhavebeenadoptedastheNorthAmericanPONstandard,EPONisthedefactoPONstandardinJapan,Korea,andsomeEuropeannations.EPONisonepartofthepopularIEEEEthernetstandardandisdesignated802.3ah.YouwillalsohearitreferredtoasEthernetinthefirstmile(EFM).Sometimesitisalsocalledthelastmile.PONTechnologies54WhilePONsprovidetheultimateinbandwidthanddatarateforhomebroadbandconnections,theyareexpensive.Carriersmustinvestinahugeinfrastructurethatrequiresrewiringtheareaserved,again.运营商必须投资庞大的基础设施，再次需要重新布线服务区域。PONTechnologies55Fiber-opticcablesaremostlylaidunderground,butthatprocessisexpensivebecauseright-of-waymustbeboughtandtrenchesdug.Cablescanbecarriedoverheadonexistingpolesatlessexpense,buttheeffectislesspleasing.光缆大多铺设在地下，但这一过程成本高昂，因为必须购买路权并挖沟。而电缆可以驾设在现有电线杆上，费用较低，但效果不太令人满意。Exercises561.Matchtheterms(1)-(6)withthedefinitionsA-F.(1)DEMUXA.adevicethatemitslightthroughaprocessofopticalamplification