第7章长途光网络解读.docx

第7章长途光网络解读.docx

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第7章长途光网络解读

Chapter7.Long-HaulOpticalNetworks

第7章长途光网络

Thischaptercoversthefollowingtopics:

此章节涵盖以下内容

∙UnderstandingLong-HaulOpticalNetworks

∙ExtendedLong-HaulOpticalNetworks

∙UltraLong-HaulOpticalNetworks

∙SubmarineLong-HaulOpticalNetworks

∙OpticalCross-Connects（OXCs）

Lighthasaninformation-carryingcapacitythatis10,000timesgreaterthanthehighestradiofrequenciesintheelectromagneticspectrum.Nowhereiscapacitymoreimportantthaninlong-haulnetworks,wherecommunicationsconvergebetweengreatmassesofpeople.Sincethe1980s,long-haulnetworkshavefollowedthelighttocreatetoday'scapaciouslong-haulopticalnetworks.

Long-haulopticalnetworksbenefitfromtwocomplementaryascendancies:

thespeedofopticalmodulation光调制的速度（Gb/s）andthedensityofopticalwavelengths光波长（λ）的密度.Bothperpetuatetheintrinsiccapacityofopticalfiber,theessentiallookingglassoflong-haulnetworking.

Long-haulopticalnetworksareclassifiedbasedonachievabledistancewithoutsignalregeneration分类取决于信号再生（无电中继传输）距离.Longhaul,extendedlonghaul,andultralonghaularedistinctdesignationsforlong-distanceopticalnetworking.

UnderstandingLong-HaulOpticalNetworks

理解长途光网络

Long-haulopticalnetworksareatthecoreofglobalinformationexchange长距离光纤网络是全球核心网信息交换.Theirprimaryapplicationisthetransportofvoice,video,anddatacommunicationsbetweendistantcitypairs主要应用在远距离的城市之间语音、视频和数据通信传输（3thOTN）.Capacityisthedefiningscarcitybecauselong-haulfiberdeploymentisalong-termcapitalasset,oftenexceeding20to30years.Beforethecommercialviabilityofwavelengthdivisionmultiplexing（WDM）,theonlywaytoaddresslong-haulcapacitywaseitherthroughbit-rateincreases,the"lighting"ofadditionaldark-fiberstrands,ordeployingnewfiberatgreatexpense.Aslong-haulnetworksapproachedfiberexhaust光纤尽duringtheboomyearsoftheInternet,WDMtechnologydeliveredonthepromiseofcapacityabundance.（DWDMpromisestosolvethe"fiberexhaust"problem）

Interexchangecarriers（IXCs）长途电信局werethefirsttodeployopticalfibercableintheirlong-haulnetworksfortransportoflong-distancevoicetraffic.TheIXCshadthemosttogainbyfuture-proofingbit-rateincreaseswithinfibermediumwhilebenefitingfromextremelylowbit-errorrates.WhileAT&Tbeganmigrationofthelong-distancenetworktofiber,MCIandSprintbuiltopticalfibernetworksfromthestart,countingonopticaltechnologytoprovideacompetitiveedgeinthelong-distancemarket.

Metropolitannetworks城域网feedlong-haulopticalnetworks.Today'sall-fiber,metropolitan,localaccessopticalnetworksaregenerallylessthanorequalto100kmorabout62miles.如今全光纤化的城域，本地接入光网络一般≤100公里，大约合62英里。

Normally,theseaccessnetworksareunamplified,makinguseoflower-costpassiveopticalcomponents使用低成本的无源光器件andpluggableITUoptics.Metropolitancorenetworksaggregatetheseaccessnetworkstogetherforthelocalserviceprovider城域核心网将这些本地服务供应商的接入网络汇聚在一起andarepositionedbetweenaccessnetworksandlong-haulnetworks.（SeeChapter6,"MetropolitanOpticalNetworks,"forafulldescription.）Manymetropolitannetworksaregrowingtoaccommodateexpandingmetros都市,andmetropolitancorenetworksupto600kmincircumferenceareincreasinglycommon.Also,newandexistingproviders新的和现有的供应商,utilities公共部门,andresearchnetworksaredeployingregionalopticalnetworks,u应用于地区光网络suallyinthe300-1000kmrange.Theresultisanumberofopticalnetworksthatcrossthelinebetweenmetropolitanandlong-hauldistinctions.

Anumberofopticalreferencesandopticalequipmentvendorsclassifyopticalnetworksbasedonthefollowing:

∙Long-haulopticalnetworkstypicallyfrom600to1000km无电中继常规长传输距离从600-1000Km（1000以下）

∙Extendedlonghaulfrom1000to2000km无电中继亚超长传输距离（Lband和采用RAMAN放大器和带外FEC）

∙Ultralonghaulfrom2000to4000km无电中继超长传输距离（减少电再生中继站、光放站的数量，延伸光放站之间的距离，有效降低系统成本）forexample3500routeKmoflonghaulfiberopticnetwork

Ofnoteisthatolder-generationequipmentneededoptical-to-electrical-to-optical（OEO）regenerationbythe600kmmarktopreservesignalintegrity.以往常规的设备需要经600公里做信号的电/光/电转换以保持信号的完整性Fromthathistoricalreference,atypicallong-haulnetworkspanwasconsideredtobe600kmbetweenopticalterminalsthatis,600kmbetweenopticalsignalregenerations.两个终端之间考虑的长度为600KmThathaschangedwithanextensionofunregenerateddistances它的延长了距离已被更改从……fromanumberofrecentopticalinnovationssuchasfiberoptimizations例如光纤优化,lowernoiseamplifiers低噪声的放大器,advancederrorcorrectioncodes先进的纠错码,andimprovedlaser不断改进的激光器andphotonicreceivertolerances.光探测器偏差

Giventhatmetropolitanandpurpose-builtregionalnetworksareblurringthefield,thischapterassumesamorecontemporarytechnologyassertionthatlong-haulnetworksbeginat600kmandfurtherclassifyintoextended扩展longhaulandultralonghaul.Foraspecificdistanceclassificationwithrespectto关于extendedandultralong-haulopticalnetwork,therangeof600to1000kmisassumedforlong-haulopticalnetworks.Theoft-quotedlong-hauldistanceof600kmisveryappropriateforTier1,city-pairreachabilityindenselypopulatednortheastAmericaandinEurope,andthereinliesadistinction:

long-haulnetworksaspiretointerconnectmajorcitiesonaninterstateorinter-countrybasis,eventomultinationalandinternationalscale.

Figure7-1depictstheselong-haulopticalnetworkclassifications.

Figure7-1.Long-HaulNetworkClassifications

[Viewfullsizeimage]

Long-haulenabledservicesareaddressingnear-termrequirementsfor2.5and10GbpstrafficprofilesincludingSONET/SDH（OC-48/STM-12andOC-192/STM-64）,EthernetLANandWANPHYsat2.5and10Gbps,2.5Gbpsand10GbpsFibreChannel,andDWDMITUgridwavelengths.Manyofthelong-haulopticalplatformshavestrategicplansfor40Gbpsbit-rateserviceswhenneeded.

Examplesoflong-haulapplicationsenabledbythesetechnologiesinclude

∙Extendedmetropolitanandregional10GigabitEthernetconnectivityAsprovidersexpandtheirnetworksandgeography,theneedforhigher-capacityEthernetservicesprovideslowerper-bandwidthcostswhileusingcustomer-friendlynetworkinterfaces.

∙High-speedtransportofSONET/SDHtoandfromtransoceanicorsubmarinecablelandingpointsofpresenceLong-haulterrestrialnetworksofteninterconnectwithmultipleinternationalnetworkconnectionpointsforthetransportofinternationalcommunicationtraffic.

∙RegionaltransportnetworksforconvergenceofoverlaynetworkplatformsManypurpose-builtnetworkbackbonesarebeingconsolidatedtohigher-capacityopticaltransportnetworkstooptimizenetworkexpenseandaddnewservices.

∙High-speedterascaleandsupercomputing,disasterrecovery,storagemirroring,andhigh-speedmultimediadistributionHigh-speedopticalnetworksarethecomputingbusbackbonesforadvancedcomputingapplicationsthatmustcollaborateoveradistributedgeography.

Long-haulnetworksmustusesingle-modefibertoreachprotracteddistancesusingasinglewavelengthsuchas1310or1550nanometers（nm）orusingmultiplewavelengthsviaDWDMinthe1550nmwindow.EarlyDWDMsystemswereheraldedbasedontheirperformanceandrawcapacities.ThecontemporaryDWDMdriveristhatofloweringthetotalcostperbitwhileremainingserviceflexible灵活的业务andcapacityscalable容量升级.

NetworksofNodes光网络节点

Long-haul,extendedlong-haul,andultralong-haulopticalsystemtopologies系统拓扑arebuiltbyconnectingopticalnodestoopticalfibercablespans光缆的跨段,oftendeployedaspoint-to-pointterminals通常配置成①点到点终端结构,meshdesigns②网格结构,orverylargerings③很大型环状结构.Long-haulopticalsystemspossesstheflexibilitytoperformseveralfunctionsthatcollectivelyperformend-to-endlong-haultransmission.Anindividualopticalnodecanbeconfiguredasthefollowing:

光网络节点分类如下：

∙Terminalnode终端型节点Thebeginningortheendofalong-haulfiberroute长途光缆路由的起始或终端节点.Terminalsitesmultiplex波分复用（合波）andamplifyincomingclient-sidesignals终端站引入客户端的信号进行合波和放大andtransmitthemtothelong-haulopticalfiberspan.然后将信号传送到长途光纤跨段Thereceivingterminalsitedemultiplexesthelong-haulcompositeDWDMsignalintoclient-sidesignalsandsendsthemtotheclientdevices接受端站波分用（分波）这些不同波长承载不同信号的光载波分开进入客户侧的信号送至客户设备Terminalsitesaregenerallythebookends,easttowest,ofaprovider'sareaofcoverage;forexample,DWDMsignalsaren'tpassedthroughtheterminalsite.OneterminalsendsDWDMsignalstowardtheeastterminalsite,whichsendsDWDMsignalstowardthewestterminalsite.Aterminalsiteoriginatesandterminateslong-haulDWDMsignals.

∙Hubnode中心型节点Asiteconfiguredasahubnodeisoftenpositionedbetweenapairofterminalsites（星型网络结构中）中心节点通常位于一对终端站中间.Thehubnodeisonethatdemultiplexes波分用allDWDMchannelsfromaparticulareastorwestdirection,中心节点是一个波分用从特定的东方向或西方向的全部DWDM波道transponds经转换（converts）,andsendsthemtoclient-attachedequipment（offofthehubnode）onthereceivepath.然后发送到支路客户设备（中心节点输出）接收通道Thehubnodealsoreceivesdirectlyattachedclienttransmitpathsignalsandtranspondstheseintoanall-channelsDWDMsignalthatistransmittedfromthehubnodeintheappropriateeastorwesttrunkdirection.

∙Opticallineamplifiernode光线路放大型节点Usuallybetweenapairofterminalsites通常位于一对终端站点中间处,amplifiestheopticalsignalwithoutdemultiplexingitorregeneratingit.放大光信号无需解复用或再生Inadditiontoreamplifyingtheopticalsignal（a1Rfunction）,放大光信号（1R功能）itgenerallyperformsotherfunctionssuchasdispersioncompensation其通常执行一些其他功能如色散补偿,bandseparation带（通道）间隔,splittingandcombining（forproperamplificationpurposes）,andrelaunchingthesignalontothenextfiberspan.Thedistancebetweenterminalsitesandotherfactorssuchasfibertypeandresultingopticalpowerbudgetd