毕业设计英文翻译1费下载

《毕业设计英文翻译1费下载》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、IntroductiontoOpticalFiberCommunicationOneofthemostimportanttechnologicaldevelopmentsduringthe1980shasbeentheemergenceofopticalfibercommunicationasamajorinternationalindustry.Oneindicationoftheextentofthisdevelopmentisthetotallengthofinstalledfiber,whichwasestim

2、atedtobe3.2millionkilometersintheU.S.alonebytheendof1987.Over90%ofthisfiberwasplacedinserviceduringthetimeperiodof1982-1987.Long-haultrunkinstallationshavebeendominated,accountingforabout95%ofthefiberintheU.S.Althoughtelecommunicationistherationalformostofthecur

3、rentinterestinfiberoptics,thiswasnotthecaseduringtheearlydaysofthetechnology.Theresearcherswhoproducedthefirstcladglassopticalfibersintheearly1950swerenotthinkingofusingthemforcommunications;theywantedtomakeimagingbundlesforendoscopy.Fiberopticswasalreadyawell-e

4、stablishedcommercialtechnologywhenthefamouspaperbyKaoandHockham,suggestingtheuseoflow-lossopticalfibersforcommunication,appearedin1966.Thefirstlow-loss(20dB/km)silicafiberwasdescribedinapublicationwhichappearedinOctoberof1970.Thedateofthispublicationissometimesc

5、itedasthebeginningoftheeraoffibercommunication.Althoughthisdevelopmentdidreceiveconsiderable6attentionintheresearchcommunityatthetime,itwasfarfrominevitablethatamajorindustrywouldevolve.The20dB/kmlossfigurewasstilltoohighforlong-haultelecommunicationsystems.Thef

6、iberswerefragile,andawaytoprotectthemwouldhavetobefound.Therewerenosuitablelightsources.Researchersdidnotknowwhetherfieldterminationandsplicingofopticalcableswouldeverbeproducedeconomicallyenoughforthetechnologytoplaya,majorroleinthemarketplace.Althoughthetechno

7、logicalbarriersappearedformidable,theeconomicpotentialwasverysignificant.Asaconsequence,researchanddevelopmentactivityexpandedrapidly,andanumberofimportantissueswereresolveduringtheearly1970s.Duringthemiddleandlate1970s,therateofprogresstowardmarketableproductsa

8、cceleratedastheemphasisshiftedfromresearchtoengineering.FiberswithlossesapproachingtheRayleighlimitof2dB/kmatawavelengthof0.8um,0.3dB/kmat1.3um,and0.15dB/kmat1.55um,w