GPON关键技术——测距.ppt

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1、GPON关键技术---测距OLT通过Ranging测距过程获取ONU的往返延迟RTD（RoundTripDelay），从而指定合适的均衡延时参数EqD（EqualizationDelay），保证每个ONU发送数据时不会在分光器上产生冲突。Ranging的过程需要开窗，即QuietZone，暂停其他ONU的上行发送通道。OLT开窗通过将BWmap设置为空，不授权任何时隙来实现。ForinstanceONU3ONU2ONU1OLTONTOLT(inCO)20km3km12kmMaincontentPhaserelationspecificationbetweenD/SandU/SC

2、onfigurationofthephasedelaypointsDefinitionsRTDmeasurementprocessMaincontentPhaserelationspecificationbetweenD/SandU/SConfigurationofthephasedelaypointsDefinitionsRTDmeasurementprocessPhaserelationspecificationbetweenD/SandU/SDuetothePONcharacteristic,theupstreamdata,receivedintheOLTisbasedo

3、nthesumofallONUstransmitteddata.Inordertoavoidsuchcollisions,atransmissionwithintheupstreamframeisassignedtoeachONU,whereonlythisspecificONUisallowedtosenddata.Inaddition,allONUsmustappearequidistantfromtheOLTforupstreamframing,i.e.,thebeginningofallupstreamframesfromallONUsshouldreachtheOLT

4、atthesametime.Inordertoachievethis,anEqualization-DelayisassignedtoeachONU.TheONUdelaystheupstreamphase,inreferencetothedownstreamphase,basedonthevalueoftheassignedEqualization-Delay.TheRangingprocessdealswiththeEqualization-Delaycalculation.TheEqualization-Delaycalculationisbasedonmeasuring

5、theroundtripdelaybetweentheOLTandeachONU.MaincontentPhaserelationspecificationbetweenD/SandU/SConfigurationofthephasedelaypointsDefinitionsRTDmeasurementprocessConfigurationofthephasedelaypointsMaincontentPhaserelationspecificationbetweenD/SandU/SConfigurationofthephasedelaypointsDefinitions

6、RTDmeasurementprocessDefinition（一）Opticalfibrepropagationdelay(Tpd)TheOpticalfibrepropagationdelay(Tpd)isduetotheopticalfibrelength/distancebetweentheOLTandONUBasictransmissiondelay(Ts)TheBasictransmissiondelay(Ts)isduetothePONsignalprocessingintheONUOpticaldelayTheOpticaldelay(TiO1,TiO2,TiS

7、1,TiS2)isduetooptoelectricalandelectro-opticalconversionintheONUandOLTEqualization-Delay(EqD)TheEqualizationdelayisaninternaldelayintheONU,setandcontrolledbytheOLT.Thepurposeofthisparameteristodelaytheupstreamtransmission,soitarrivesattheOLTattheco