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InternationalTelecommunicationUnionITU-TG.657TELECOMMUNICATIONSTANDARDIZATIONSECTOROFITU(12/2006)SERIESG:TRANSMISSIONSYSTEMSANDMEDIA,DIGITALSYSTEMSANDNETWORKSTransmissionmediaandopticalsystemscharacteristics–OpticalfibrecablesCharacteristicsofabendinglossinsensitivesinglemodeopticalfibreandcablefortheaccessnetworkITU-TRecommendationG.657ITU-TG-SERIESRECOMMENDATIONSTRANSMISSIONSYSTEMSANDMEDIA,DIGITALSYSTEMSANDNETWORKSINTERNATIONALTELEPHONECONNECTIONSANDCIRCUITSG.100–G.199GENERALCHARACTERISTICSCOMMONTOALLANALOGUECARRIER-TRANSMISSIONSYSTEMSG.200–G.299INDIVIDUALCHARACTERISTICSOFINTERNATIONALCARRIERTELEPHONESYSTEMSONMETALLICLINESG.300–G.399GENERALCHARACTERISTICSOFINTERNATIONALCARRIERTELEPHONESYSTEMSONRADIO-RELAYORSATELLITELINKSANDINTERCONNECTIONWITHMETALLICLINESG.400–G.449COORDINATIONOFRADIOTELEPHONYANDLINETELEPHONYG.450–G.499TRANSMISSIONMEDIAANDOPTICALSYSTEMSCHARACTERISTICSG.600–G.699GeneralG.600–G.609SymmetriccablepairsG.610–G.619LandcoaxialcablepairsG.620–G.629SubmarinecablesG.630–G.639FreespaceopticalsystemsG.640–G.649OpticalfibrecablesG.650–G.659CharacteristicsofopticalcomponentsandsubsystemsG.660–G.679CharacteristicsofopticalsystemsG.680–G.699DIGITALTERMINALEQUIPMENTSG.700–G.799DIGITALNETWORKSG.800–G.899DIGITALSECTIONSANDDIGITALLINESYSTEMG.900–G.999QUALITYOFSERVICEANDPERFORMANCE–GENERICANDUSER-RELATEDASPECTSG.1000–G.1999TRANSMISSIONMEDIACHARACTERISTICSG.6000–G.6999DATAOVERTRANSPORT–GENERICASPECTSG.7000–G.7999PACKETOVERTRANSPORTASPECTSG.8000–G.8999ACCESSNETWORKSG.9000–G.9999Forfurtherdetails,pleaserefertothelistofITU-TRecommendations.ITU-TRec.G.657(12/2006)iITU-TRecommendationG.657CharacteristicsofabendinglossinsensitivesinglemodeopticalfibreandcablefortheaccessnetworkSummaryWorldwide,technologiesforbroadbandaccessnetworksareadvancingrapidly.Amongthese,thetechnologyapplyingsinglemodefibreprovidesforahigh-capacitytransmissionmediumwhichcananswerthegrowingdemandforbroadbandservices.Theexperiencewiththeinstallationandoperationofsinglemodefibreandcablebasednetworksishuge,andITU-TRecommendationG.652describingitscharacteristicshasbeenadaptedtothisexperience.Nevertheless,thespecificuseinanopticalaccessnetworkputsdifferentdemandsonthefibreandcablewhichimpactsitsoptimalperformancecharacteristics.Differenceswithrespecttotheuseinthegeneraltransportnetworkaremainlyduetothehighdensitynetworkofdistributionanddrop-cablesintheaccessnetwork.Thelimitedspaceandthemanymanipulationsaskforoperatorfriendlyfibreperformanceandlowbendingsensitivity.Inaddition,thecablinginthecrowdedtelecomofficeswherespaceisalimitingfactorhastobeimprovedaccordingly.ItistheaimofITU-TRecommendationG.657tosupportthisoptimizationbyrecommendingstronglyimprovedbendingperformancecomparedwiththeexistingG.652singlemodefibreandcables.Thisisdonebymeansofintroducingtwoclassesofsinglemodefibres,oneofwhich,classA,isfullycompliantwiththeG.652singlemodefibresandcanalsobeusedinotherpartsofthenetwork.Theotherclass,classB,isnotnecessarilycompliantwithG.652butiscapableoflowvaluesofmacrobendinglossesatverylowbendradiiandispre-dominantlyintendedforin-buildinguse.SourceITU-TRecommendationG.657wasapprovedon14December2006byITU-TStudyGroup15(2005-2008)undertheITU-TRecommendationA.8procedure.iiITU-TRec.G.657(12/2006)FOREWORDTheInternationalTelecommunicationUnion(ITU)istheUnitedNationsspecializedagencyinthefieldoftelecommunications.TheITUTelecommunicationStandardizationSector(ITU-T)isapermanentorganofITU.ITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommendationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationAssembly(WTSA),whichmeetseveryfouryears,establishesthetopicsforstudybytheITU-Tstudygroupswhich,inturn,produceRecommendationsonthesetopics.TheapprovalofITU-TRecommendationsiscoveredbytheprocedurelaiddowninWTSAResolution1.InsomeareasofinformationtechnologywhichfallwithinITU-T'spurview,thenecessarystandardsarepreparedonacollaborativebasiswithISOandIEC.NOTEInthisRecommendation,theexpressionAdministrationisusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.CompliancewiththisRecommendationisvoluntary.However,theRecommendationmaycontaincertainmandatoryprovisions(toensuree.g.interoperabilityorapplicability)andcompliancewiththeRecommendationisachievedwhenallofthesemandatoryprovisionsaremet.Thewordsshallorsomeotherobligatorylanguagesuchasmustandthenegativeequivalentsareusedtoexpressrequirements.TheuseofsuchwordsdoesnotsuggestthatcompliancewiththeRecommendationisrequiredofanyparty.INTELLECTUALPROPERTYRIGHTSITUdrawsattentiontothepossibilitythatthepracticeorimplementationofthisRecommendationmayinvolvetheuseofaclaimedIntellectualPropertyRight.ITUtakesnopositionconcerningtheevidence,validityorapplicabilityofclaimedIntellectualPropertyRights,whetherassertedbyITUmembersorothersoutsideoftheRecommendationdevelopmentprocess.AsofthedateofapprovalofthisRecommendation,ITUhadnotreceivednoticeofintellectualproperty,protectedbypatents,whichmayberequiredtoimplementthis