《通信与电子信息科技英语》课件-unit 12

FiberOpticNewwordsandphrases

1fibern.纤维

fiberoptic(opticalfiber)光纤(光纤电缆)2innovationn.革新，技术革新，新方法3immunityn.抗扰性，免除性，免疫(性)immuneadj.免疫的;免受(伤害)的4directvt.引导，导引5propagatev.传播6refractionn.折射，折射度

refractvt.折射refractiveadj.折射的7indexn.指数，指标，索引

(pl.indices)refractiveindex（indexofrefraction）折射率8externaladj.外部的；n.外部,外面

externalinterference外界干扰9interceptionn.截取，窃听，监听10abundantadj.丰富的,充裕的11perceivev.察觉,感知FiberOptic12appreciationn.了解,懂得13sinen.正弦14incidencen.入射

angleofincidence（incidenceangle）入射角15criticaladj.临界的，决定性的，极限的

criticalangle临界角16dielectricn.电介质,绝缘材料17waveguiden.波导,波导管18coren.（光纤）纤芯19claddingn.包层20sheathn.外皮，护层21jacketn.护套，外壳22governv.支配，决定，起决定影响23assemblyn.装配,组合FiberOptic24radiusn.半径(pl.radii)25possessvt.有，具有，拥有26knotn.结点，节27diametern.直径28wavelengthn.波长29nanometern.纳米，毫微米30perpendicularadj.垂直的，正交的

perpendicularto与……垂直，垂直于31zigzagadj.之字形的，Z字形的32opaqueadj.不传导的,不透明的33destructiveadj.破坏(性)的destructivelyadv.破坏地34modaladj.n.模态(的)，形式(上的)35bouncevi.反跳(弹);反射36broadenvt.加宽，扩展FiberOptic37differentiatevt.区分,区别38predefinen.预先确定（规定），预定义39precludevt.阻碍，妨碍40outlinevt.略述，概括地论述41uniformadj.均匀的，一致的42mono(前缀)单，单一，一monomoden.单模43dispersionn.色散44profilen.曲线，分布图refractiveindexprofile折射率分布45devisevt.设计，发明46chromaticadj.有色的，彩色的chromaticdispersion色散1comeofage成年,到法定年龄,发达,充分发展2freedomfrom免除3attheedgeof在……的边缘4Snell’slaw斯涅尔（折射）定律

FiberOptic5multimodefiber多模光纤6singlemodefiber(singlemodefiber)单模光纤7cladfiber包层光纤,涂层纤维8parallelto与……平行,平行于9lightray光线10lightbeam光束11backandforth来来往往地,来回地12modesofpropagation（propagationmode）传播模，传播波型13multimodepropagation多模传播14opticalreceiver光接收器

opticalcommunicationreceiver光通信接收机15errorrate误码率FiberOptic16destructiveinterference破坏性干扰，相消(性)干扰17gradedindexfiber渐变折射率光纤

gradedindexmultimodefiber渐变折射率多模光纤18steppedindexfiber阶跃折射率光纤19intermodaldispersion模间色散

FiberOptic

Opticalfibertransmissionhascomeofageasamajorinnovationintelecommunications.Suchsystemsofferextremelyhighbandwidth,freedomfromexternalinterference,immunityfrominterceptionbyexternalmeans,andcheaprawmaterials(silicon,themostabundantmaterialonEarth).FundamentalsofFiberOpticSystemsOpticalfibersguidelightrayswithinthefibermaterial.Theycandothisbecauselightraysbendorchangedirectionwhentheypassfromonemediumtoanother.Theybendbecausethespeedofpropagationoflightineachmediumisdifferent.Thisphenomenoniscalledrefraction.Onecommonexampleofrefractionoccurswhenyoustandattheedgeofapoolandlookatanobjectatthebottomofthepool.Unlessyouaredirectlyovertheobject,itappearstobefartherawaythanitreallyis.Thiseffectoccursbecausethespeedofthelightraysfromtheobjectincreasesasthelightrayspassfromthewatertotheair.Thiscausesthemtobend,changingtheangleatwhichyou

FiberOpticperceivetheobject.themtobend,changingtheangleatwhichyouperceivetheobject.YoucanobtainanappreciationforthemannerbywhichlightflowsbyfocusinguponSnell’sLaw.Snell’sLawHowopticalfibersworkcanbeexplainedbySnell’sLaw,whichstatesthattheratioofthesineoftheangleofincidencetothesineoftheangleofrefractionisequaltotheratioofthepropagationvelocitiesofthewaveinthetworespectivemedia.Thisisequaltoaconstantthatistheratiooftherefractiveindexofthesecondmediumtothatofthefirst.Writtenasanequation,Snell’sLawlookslikethis:sinA1/sinA2=V1/V2=K=n2/n1Inthisequation,A1andA2aretheanglesofincidenceandrefraction,respectively.V1andV2arethevelocitiesofpropagationofthewaveinthetwomedia.n1andn2aretheindicesofrefractionofthetwomedia.

TheparametersaredemonstratedgraphicallyinFig.12.1.Ineachcase,

A1istheangleofincidence,andA2istheangleofrefraction.Theindex

ofrefraction(n1>n2)ofrefractionofmaterial1,n1,isgreaterthantheindexofrefractionofmaterial2,n2.Thismeansthatthevelocityof

FiberOpticpropagationoflightisgreaterinmaterial2thaninmaterial1.Fig.12.1(a)demonstrateshowalightraypassingfrommaterial1tomaterial2isrefractedinmaterial2whenA1islessthanthecriticalangle.Fig.12.1(b)demonstratestheconditionthatexistswhenA1isatthecriticalangleandtheangleA2isat90［dg］.Thelightrayisdirectedalongtheboundarybetweenthetwomaterials.AsshowninFig.12.1(c),anylightraysthatareincidentatanglesgreaterthanA1ofFig.121(.b)willbereflectedbackintomaterial1withangleA2equaltoangleA1.TheconditioninFig.12.1(c)istheoneofparticularinterestforopticalfibers.

ExercisesⅠ.PleasetranslatethefollowingwordsandphrasesintoChinese.1.lightbeam2.propagationmode3.refractiveindexprofile4.chromaticdispersion5.opticalreceiver6.externalinterference7.errorrate8.dielectric9.lightray10.cladfiber11.destructiveinterference12.steppedindexfiber

光束传播模折射率分布色散光接收器外界干扰误码率电介质,绝缘材料光线包层光纤，涂层纤维破坏性干扰，相消(性)干扰阶跃折射率光纤ExercisesⅡ.PleasetranslatethefollowingwordsandphrasesintoEnglish.1.波导（管）2.临界角3.纳米4.光纤通信系统5.光纤传输6.单模光纤7.渐变折射率多模光纤

waveguidecriticalanglenanometeropticalcommunicationssystemopticalfibertransmissionsinglemodefiber(singlemodefiber)gradedindexmultimodefiberExercises8.波长9.斯涅尔定律10.折射率11.折射角12.破坏性干扰13.多模传输14.光通信接收机15.入射角16.光纤

wavelengthSnell’slawrefractiveindex(indexofrefraction)refractionangle(angleofrefraction)destructiveinterferencemultimodetransmissionopticalcommunicationreceiverangleofincidence(incidenceangle)fiberoptic(opticalfiber)

ExercisesⅢ.Fillintheblankswiththemissingword(s).1.Opticalfibertransmissionhascome

of

ageasamajorinnovationintelecommunications.2.Theraypropagates

in

thiszigzagfashiondownthecoreuntilitreachestheotherend.3.LightrayAentersthefiberperpendicular

to

thefaceofthecoreandparallel

to

theaxis.4.Inadditiontopointers,asignificantportionoftheoverheadbytes

in

theSTS1framearereservedformanagementdata,enablingnetworkmanagementfunctionstoincludeloopback,biterrorratetesting,andcollectionandreportingofperformancestatistics

tobe

carried(carried,tobecarried,carrying,havingcarried)withintheSONETframe.5.Thisisbecausemodaldelayspreadingbroadensthepulsesin

thetimedoain.

Exercises6.Raysenteringthefiber

at

differinganglesarerefractedvaryingnumbersoftimesastheymovefromoneend

to

theotherandconsequentlydonotarriveatthedistantend

with

thesamephaserelationshipaswhentheystarted.7.Theeffectofpulsespreadingistomakeitdifficultorimpossibleforanopticalreceivertodifferentiateonepulse

from

anotherafteragiventransmissiondistance.8.Becausemostopticalcommunicationssystemstransmitinformationin

digitalformconsistingofpulsesoflight,theeffectofmodaldelayspreadinglimitsthecapabilityofthefiber

totransport

(transporting,totransport,transported)recognizablepulses.9.Theresultofthedifferenceintherefractiveindiceskeepslight

flowing(flowing,flow,flowed,toflow)throughthecoreafteritgetsintothecore,evenifthefiberis

bent

(bent,bending,bend)or

tied(tied,tying,tie)intoaknot.10.Therayentersintothecladdingandpropagatesinto,orisabsorbed,into

thecladdingandjacket(whichisopaquetolight).

ExercisesⅣ.Answerthefollowingquestionsaccordingtothetext.1.Whatarethebenefitsofopticalfibertransmissionsystems?Opticalfibersystemsofferextremelyhighbandwidth,freedomfromexternalinterference,immunityfrominterceptionbyexternalmeans,andcheaprawmaterials(silicon,themostabundantmaterialonEarth).2.TelltheSnell’slawinyourownwordsinEnglish.Theratioofthesineoftheangleofincidencetothesineoftheangleofrefractionisequaltotheratioofthepropagationvelocitiesofthewaveinthetworespectivemedia.Exercises3.Pleasegivesometypicalparametervaluesdesignedforamultimodefiber.Followingaresometypicalvaluesforamultimodefiber:Anoperatinglightwavelengthof0.8micrometers(μm)Acoreindexofrefractionncof1.5Acladdingindexofrefractionnof1.485(=0.99nc)Acorediameterof50,62.5,or100μmAcladdingthicknessof37.5μm4.Whatisamultimodefiberandwhatisasinglemodefiber?Whatarethedifferencesbetweenthem?Singlemodefiber,alsoknownasmonomode,hasau