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Fiber Testing—The Fundamentals for Successful Broadband Deployment

IntroductionThis document sets the test requirements for qualifying the fiber portion of a fiber-to-the-home (FTTH) net-work prior to equipment installation and turn-up. The steps for this stage are:• inspectingandcleaningconnectorsandconnections• qualifyingtheloss,opticalreturnloss(ORL),anddistanceofthelink,usingeitheranopticaltimedomain

reflectometer(OTDR)orlosstestset

Various access points can be used in qualifying the FTTH network as Figure 1 shows.

Figure 1. Possible access points for FTTH network qualification

Connection Qualification of the Link

Contamination is the #1 cause for troubleshooting in optical networks.Asingleparticlematedintothecoreofafibercancausesignificantbackreflection(alsoknownasreturnloss),insertionloss,andequipmentdamage.Visualinspectionistheonlywaytodetermineiffiberconnectorsaretruly clean before mating them.

Implementing a simple yet important process of proactive visual inspection and cleaning can eliminate poor optical signal performance and avoid potential equipment damage.

T-BERD/MTS-4000OTDR

Feeder Fiber

SplitterLocation

Distribution Fibers

Drop Terminal

Drop Terminal

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Testing Alone is Not EnoughCurrently,theonlytoolconsideredessentialtofibertechniciansistheopticalpowermeter(OPM),whichmea-surestheenergypresentinanopticalfiber,allowingthemtodetermineifenoughpowerexiststosupporttheapplication,oriftheattenuationofthelinkmeetsspecification.Testing fiber signal strength alone is no longer considered adequate because optical fiber troubleshooting statis-tics revealed contamination as the number one cause of poor physical network performance. High-bandwidth equipment manufacturers and their installation teams first discovered the impact of contamination on net-workperformance.Theirexperiencerevealedthateventhebestcleanmanufacturingpracticescannotpreventmicroscopicparticlesfromenteringsealedbagsorunderdustcaps,creatingpotentialcontaminationeveninbrand new components.Just one microscopic particle on the fiber end face can become permanently embedded into the fiber core duringmating.Onceembeddedinthecore,theparticlecancausesignificantbackreflectionandinsertionloss—two primary causes of poor network performance.BecausetheOPMcannotdetectmicroscopicparticlesonafiberpriortomating,testingalonebeforematingisnot enough. The only way to ensure a fiber is truly clean before mating is through proactive visual inspection using a microscope designed specifically for inspecting optical fiber.

The Case for Proactive InspectionBecausemicroscopiccontaminationisalwaysapossibility,eveninnewfibercomponents,thefullpotentialfora low-loss fiber connection is only realized when technicians ensure that no contamination is present prior to itsfirstmating.Thisassuranceisonlypossiblethroughmicroscopicvisualinspectionofeveryfiber,everytime,beforeitismated,whichdefinessystematicproactiveinspection.Anyone familiar with the physical layer of a network understands the potential for contamination once the fiber isinthenetworkenvironment.Therefore,itisessentialthattechnicianspracticesystematicproactiveinspec-tion every time they handle a fiber to ensure optimal network performance.Not practicing systematic proactive inspection leads administrators running the risk of installing dirty fiber that willimpairtheopticalsignalanddecreasenetworkperformance.Matingdirtyfiberscarriestheadditionalriskofembeddingdirtintothefiber,whichcanresultinpermanentdamagetothefiberandtheconnectingnet-work equipment—all of which may lead to future network interruption when fiber repolishing or replacement becomes necessary.Additionally,discoveringfiberdamagetocostlynetworkequipmentfromembeddeddirtafterinstallationreducesthechanceforreplacingorrepolishingthefiberasanoption,makingfuturetroubleshootingcosts,assetdamage,andnetworkdowntimeexponentiallyhigher.Conversely,withsystematicproactiveinspection,thefibercanalmostalwaysbecleaned,completelyeliminatingthepotentialforfibercontamination,networkdowntime,andpermanentequipmentdamage.The impact of contamination on network performance and the benefits of systematic proactive inspection led theInternationalElectronicsManufacturingInitiative(iNEMI)toconductpracticalresearchwithfindingsthatbecame the pillar for the international standard IEC-61300-3-35.This standard specifies the use of visual inspection procedures and pass-fail criteria to achieve the measurable benefits associated with proactive inspection. Equipping technicians with a model based on this IEC standard that outlines proactive inspection procedures and pass-fail criteria is key to ensuring that technicians correctly carry out proactive inspection every time.

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Benefits of Proactive InspectionCompanies that have adopted proactive inspection on a large scale have significantly reduced the need for troubleshootingandhaveloweredoperatingcosts,showingthattheoperationalbenefitsofproactiveinspec-tion clearly outweigh the costs.Companies can reduce the need for troubleshooting as well as network downtime and maintenance costs. Keeping the network active and users online improves productivity. And because proactive inspection ensures thatnetworkcomponentsoperateattheirhighestlevelofperformance,itcanoptimizesignalandnetworkperformance,preventnetworkdamage,andprotectequipmentandtechnologyinvestment.It is easy to make the connection between these benefits associated with proactive inspection of optical fiber in the network and the bottom line.

Barriers to Proactive InspectionInspiteoftheseconsiderablebenefits,proactiveinspectionisnotsystematicallypracticed,whichcanbesur-misedinpartbythedisparitybetweenthenumberofOPMssoldin2008(around60,000)andthenumberofopticalinspectiondevicessoldinthesameyear(around7,000).Thesefiguresillustratethefirstoftwobarriersto proactive inspection: the equipment costs associated with the purchase of the optical fiber inspection device. The second barrier: the time costs associated with the addition of proactive inspection to the optical fiber han-dling process.Whilereal,thesecostsaresignificantlylessthanthoseassociatedwithreactiveinspectionresultingfrompoornetworkperformance.Thisfact,coupledwiththefinancialandproductivitybenefitsofproactiveinspectionshould compel network administrators to make efforts to overcome these barriers.

Overcoming Barriers to Proactive InspectionIn the effort to help network administrators and technicians overcome barriers to systematic proactive inspec-tion,suchastimeandcost,theauthorsofthiswhitepaperproposedoingoneorbothofthefollowing:1.AdoptingtheuseofahandheldintegratedOPM/inspectiondevicewithapatchcordmodule.Theseinspec-tiondevices,basedonestablishedIECfiberinspectionstandards(IEC-61300-3-35),areessentialtothefiberhandling process.

2.AddinganoptionalfiberinspectionprobeonanOTDR.SomeOTDRsofferthiscapabilitythroughaUSBportconnection,whichallowsforquickandeasyinspectionofconnectorendfacesforcontaminationandalso enables capturing the image and storing it in jpeg format.

These tools help facilitate the Inspect Before You ConnectSM process and also enable a seamless workflow for inspecting and testing.

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Seamless Testing WorkflowTopromotesystematicallyadoptingproactiveinspection,JDSUdevelopedtheproactiveinspectionmodel“InspectBeforeYouConnect,”whichpromotesthevisualinspectionproceduresandpass/failcriteriasetforthintheIEC-61300-3-35visualinspectionstandard.Byguidingtechnicianswithvaryinglevelsofexpertiseintheproperimplementationofproactiveinspection,theadditionofthismodeltofiberhandlingessentialsensuresthat proactive inspection is performed correctly every time.

Proactive Inspection ModelThis simple inspection process will ensure fiber end faces are clean prior to mating connectors:

Step 1 Inspect:Usethemicroscopetoinspectthefiber.Ifthefiberisdirty,gotostep2.Ifthefiberisclean,gotostep4.

Step 2 Clean: Ifthefiberisdirty,useacleaningtooltoclean the fiber end face.

Step 3 Inspect:Usethemicroscopetore-inspectandconfirmthefiberisclean.Ifthefiberisstilldirty,gobacktostep2.Ifthefiberisclean,gotostep4.

Step 4 Connect: If both the male and female connectors areclean,theyarereadytoconnect.

1 INSPECT PATCH CORD 2 ACTIVATE PROBE 3 INSPECT BULKHEAD 4 CONNECT 5 TEST

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Fiber Connector End Face Inspection ZonesInspection zones reveal a series of concentric circles that identify areas of interest on the connector end face. The inner-most zones are more sensitive to contamination than outer zones.

Figure 2. Fiber connector end face inspection zones

Severalcommonlyknownfiberendfacedefectsarecontamination,particles,pits,chips,scratches,loosecon-tamination,andembeddedcontamination.

Figure 3. Fiber connections and various connector end face views as seen through an inspection scope

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IdeallythefiberendfaceshouldbefreefromdefectsorscratchesasFigure4shows.

Figure 4. Microscopic views of clean connector end faces

Optical Fiber Interface InspectionInspectingfiberendfacecanbeperformedusingtwodifferentmethods.Ifthecableassemblyisaccessible,youcaninserttheconnectorferruleintothemicroscopetoconducttheinspection,whichisgenerallyreferredtoasapatchcordinspection.Iftheconnectoriswithinamatingadaptoronthedeviceorpatchpanel,inserta“probe”microscope into the open end of the adaptor to view the connector inside; this is known as inspection through thebulkhead/adaptorconnector.

Patchcord InspectionSelecttheappropriatetipthatcorrespondstotheconnectortypethatyouwishtoinspectandattachitontothemicroscope.

Insert the connector into the tip as shown in Figure 5 and adjust the focus to inspect.

Figure 5. Patchcord microscope inspection

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Inspection through the Bulkhead/Adaptor ConnectorSelecttheappropriatetip/probethatcorrespondstotheconnectortypeforthebulkheadoradaptorconnectoryou wish to inspect and attach it to the probe microscope. Insert the probe into the bulkhead or adaptor connec-tor and adjust the focus to inspect.

Figure 6. Microscope Inspection through the bulkhead/adaptor connector

Loss, ORL, and Distance Qualification of the LinkTwoseparatetoolsareavailableforloss,ORL,anddistancequalification.Whichtooltoselectwilldependupontheexpertiseoftheuseraswellasthecomplexityofthenetwork.Networksusingvideooverlay(1550nm)andhighpowerlevelsrequireORLmeasurements.OtherwiseORLmeasurementsareoptional.ExpertuserspreferOTDRtesttools,asthisisasingle-endedtest,howeverthetraceanalysisofapassiveopticalnetwork(PON)isquitecomplexandbecomesevenmoredifficulttointerpretoncomplexPONswith cascaded networks and when testing directly from the central office to the customer premises. Furthermore,whilethebidirectionalOTDRtestingmethodisthemeasurementofreferencewithintheinternationalstandard,unidirectionalOTDRtestingleadstolessaccuratelossresults,exceptwhenthe backscattered coefficient of fibers used along the network are similar (see the Bidirectional Analysis chapteroftheReferenceGuidetoFiberOpticTestingVolume1forfurtherinformation).Otheruserspreferlosstestset/ORLmeters,becauseofitseasyoperationandintuitiveresultsanalysis.However,thismethodrequirestwopeopletoperformthetestandatseveraldifferentlocations.Shouldaproblemarise,useofanOTDRisthenrequiredtolocate/identifytheissuealongthelink.SeeFigure7whichillustratesusesofanOTDRinacceptancetesting.

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Using an OTDR

Figure 7. Qualifying a FTTH network with an OTDR

InadditiontousingtheOTDRasaqualificationtool,itcanalsobeusedasatroubleshootingtooltopinpointissues along the link. Another simple tool that can easily troubleshoot fiber issues is the visual fault locator (VFL),whichisthestandardtoolforfibertestingcrews.

OTDR Test Alternative 1: Independently testing the feeder and the distribution cables from the splitter locationFirst,conductanOTDRtestofthefeederandthedistributioncablesindependentlyfromthesplitterlocationtoeliminate a truck roll. This test can easily qualify the network without qualifying the splitter and only validates the splitter(s) connection(s) during turn-up of the system with a power meter.Performingthemeasurementswithtwowavelengthsismandatorytoidentifypossiblebendsalongthelinkasindicated by higher loss at 1550 nm than at 1310 nm at the bend location.Tofullyqualifythenetworkconnectoratthebeginningandattheendofthelink,usetwo300mminimumlaunch cables (launch cable and received cables).Ifusingalaunchcable,connecttheOTDRtothelaunchcable,andthenthelaunchcabletotheconnectorgoingtotheopticalnetworktermination(ONT)port.Otherwise,justconnecttheOTDRtothenetwork.Ifusingareceivecable,alsoconnectitattheotherendofthelink.

Acceptance testing with OTDR• Connectorized splitter: Link/event insertion loss & ORL of the feeder part at 1310/1550 nm Link/event insertion loss & ORL of the distribution part at 1310/1550 nm• Spliced splitter: Link/event insertion loss & ORL between OLT and ONT at 1310/1550 nm

Central O�ce

1310 nm

1490/1550 nm

PON OLT

Video AMP

RF Video

T-BERD/MTS-4000OTDR

T-BERD/MTS-4000OTDR

T-BERD/MTS-4000OTDR

Feeder Fiber

Drop Terminals

Passive Splitter

ONT

ONT

ONT

ONT

Distribution FibersWDM

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SetthefollowingparametersfortheOTDR:• selecttheconstruction(orexpert)mode• selectthepulsewidthbetween10and100ns• selecttherangeforslightlylongerthantherangeofthelink• settheresolutiontoAuto• settheacquisitiontimeto30s• setthelaunch/receivecable,ifanyPerformanacquisitionusingtheSTARTkey.Attheendoftheacquisition,aresultscreenshouldappearsimilartotheoneshowninFigure8below:

Figure 8. Feeder or distribution cable test only

Theshortdistanceofthedistributionlinklimitsthenumberofeventsdisplayedonthetable(usuallyone,buttheremayhavealsobeenmechanicalsplicesorconnectorsalongthelinkaswell).TheexampleinFigure8showsonlyoneevent,whichistheclosestsplitterlocation.

OTDR Test Alternative 2: Testing from the customer premises/ONT toward the central office/OLTPerformanOTDRtestfromtheONTtofullyqualifythenetworkbetweentheONTandtheOLT.Forqualifyingnetworksusinguptoa1x32splitter(cascadedornot),werecommendusingtheJDSUMTS-4000withits8126MA1310/1550nmOTDRmodule.Forqualifyinganytypeofnetwork(includingupto1x128),werecommendusingtheJDSUMTS-6000withits1310/1550nm8126LROTDR.Performingthemeasurementswithtwowavelengthsismandatorytoidentifypossiblebendsalongthelinkasindicated by a higher loss at 1550 nm than at 1310 nm at the bend location.Tofullyqualifythenetworkconnectoratthebeginningandattheendofthelink,usetwo300mminimumlaunch cables (launch cable and receive cables).

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Ifusingalaunchcable,connecttheOTDRtothelaunchcable,andthenthelaunchcabletotheconnectorgoingtotheONTport.Otherwise,justconnecttheOTDRtothenetwork.Ifusingareceivecable,alsoconnectitattheother end of the link.SetthefollowingparametersfortheOTDR:• selecttheconstruction(orexpert)mode• selectthepulsewidthbetween100and300nstoqualifythroughthesplitter,orbetween10and100nsto

qualify up to the splitter• selecttherangeforslightlylongerthantherangeofthelink• settheresolutiontoAuto• settheacquisitiontimeto30s• setthedetectionofthesplitterasAuto• setthelaunch/receivecable,ifanyPerformanacquisitionusingtheSTARTkey.Attheendoftheacquisition,aresultscreenshouldappearsimilartotheoneshowninFigure9below,for distribution qualification only:

Figure 9. Distribution test only from ONT to first splitter, without launch cable

Theshortdistanceofthedistributionlinklimitsthenumberofeventsdisplayedonthetable(usuallyone,buttheremayhavealsobeenmechanicalsplicesorconnectorsalongthelinkaswell).TheexampleinFigure9showsonlyoneevent,whichistheclosestsplitterlocation.

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ForcompletePONqualificationfromtheONT:

Figure 10. Cascaded splitter network test from ONT, without launch cable

Testingthroughthesplitterprovidesatableofresultswiththesplitter(s)losses,thefiberend,aswellaseventuallyconnector/splicelosses.Figure10aboveshowstwosplitters,eachgivingaround9dBofloss,atypicalvaluefor1x8splitterswiththefiberendataround3044meters.

OTDR Test Alternative 3: Testing from the central office/OLT toward the customer premises/ONTTestingfromthecentralofficerequiresagoodunderstandingoftheOTDRtrace,becauseintestingfromthecentralofficetheOTDRtracedisplaysallthevariouslegsafterthesplitterwithoutdifferentiatingthemalongthetrace.Therefore,thetableofresultsrequiresexpertinterpretationanddetailedanalysisofthenetworklayout.Forqualifyingnetworkusingupto1x32splitter(cascadedornot),werecommendusingtheJDSUMTS-4000withits8126MA1310/1550nmOTDRmodule.Forqualifyinganytypeofnetwork(includingupto1x128),werecommendusingtheJDSUMTS-6000withits1310/1550nm8126LROTDR.Performingthemeasurementswithtwowavelengthsismandatorytoidentifyanypossiblebendsalongthelinkas indicated by a higher loss at 1550 nm than at 1310 nm at the bend location.Tofullyqualifythenetworkconnectoratthebeginningandattheendofthelink,usetwo300mlaunchcables(launch cable and receive cables).Ifusingalaunchcable,connecttheOTDRtothelaunchcable,andthenthelaunchcabletotheconnectorgoingtotheONTport.Otherwise,justconnecttheOTDRtothenetwork.Ifusingareceivecable,alsoconnectthereceived cable at the other end of the link.

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SetthefollowingparametersfortheOTDR:• selecttheconstruction(orexpert)mode• selectthepulsewidthbetween100and300nstoqualifythroughthesplitter,orbetween10and100nsto

qualify up to the splitter• selecttherangeforslightlylongerthantherangeofthelink• settheresolutiontoAuto• settheacquisitiontimeto30s• setthedetectionofthesplitterasAuto• setthelaunch/receivecable,ifanyPerformanacquisitionusingtheSTARTkeyAttheendoftheacquisition,aresultscreenshouldappearsimilartotheoneshowninFigure11belowfor Feeder test only:

Figure 11. Feeder test only from the OLT to first splitter, without launch cable

Theshortdistanceofthefeederlinklimitsthenumberofeventsdisplayedonthetable(usuallyone,buttheremayhavealsobeenmechanicalsplicesorconnectorsalongthelinkaswell).TheexampleinFigure11showsonlyoneevent,whichistheclosestsplitterlocation.

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Figure 12. Cascaded splitter network test from OLT, without launch cable

Testingthroughthesplitterprovidesatableofresultswiththesplitter(s),thelegends(whichmaynotallbeshownbecausetheycanbeatsimilardistancesfromtheOLTand,therefore,hiddenontheOTDRtrace),aswellaseventuallyconnector/splicelocations.Theexampleaboveshowstwosplittersandmultiplelegs.However,notknowingtheexactlayoutofthenet-workmakesitverydifficulttointerpretthetableofresultsafterthefirstsplitterbecauseitdoesnotexactlyrepresentthelossoftheindividualevents(splitters,connectors,legends,splices),ratheritrepresentsthelossofthe individual events together with the results from the other legs.Thereforewearelefttoanalyzetheinformationfromfeedertothefirstsplitter,andthenthedistancesofthefollowingeventsthatareshownintheOTDRtraceandeliminatingtheirlossesprovidedinthetableofresults.

Result AnalysisAfterperformingtheacquisition,comparetheresultstothoseexpectedaccordingtonetworkandcustomerstandards.TheOTDRservesasaqualificationtoolaswellasatroubleshootingtool,therefore,troubleshootinginformationisautomaticallyprovidedincaseofproblems.Section3providestypicalacceptancevalues.WhenusinganOTDR,especiallywhennotusinglaunchcables,itisimportanttonotethattheinsertionlossvaluesmaynotintegratethelossandreflectance(andthereforeORL)oftheconnectorsatthebeginningand/ortheendofthelink.Ifusinglaunchcables,setthisundertheOTDRsetupwhennecessary.CurrentissuesencounteredwithPONnetworksaredefinedbelow:• Nofiberdetected—Check/cleantheconnectionbetweentheOTDRandthenetworkanduseaVFLto

investigate the presence of a bend or break along the patch panel.• Distancediffersfromtheexpected—Indicatesthepresenceofabreakalongthelinkorthefibertested.

Check the fiber number to ensure it is the correct fiber selection with the correct continuity.• Totallossisgreaterthanexpected—Lookatthetableofeventsforlargesplices,connectors,orbends.• ORLisworsethanexpected(asmallernumber,suchas30dBvs.40dB,indicatespoorORL)—Lookatthe

tableofeventsforindicationsofbadreflectancevaluesandchecksectionalizedORLontheOTDRtrace.

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Using a Loss Test Set/ORL MeterAlosstestset/ORLmetercanbeusedforend-to-endtestingexceptwhenissuesarefoundwhichthenrequirestheuseofadditionaltoolssuchasanOTDRorVFL.ForqualifyingaPONnetwork,JDSUrecommendsusingitsOLT-55/ORL-551310/1550nm,asshowninFigure13,ortheT-BERD/MTS-6000withits8126OFI11310/1550nmlosstestset/ORLmodule.Testingat1490nmgenerallyisunnecessaryasitdoesnotaddinformationfoundat1550nm,however,itisavail-able.Performingmeasurementswithtwowavelengthsismandatoryforidentifyingpossiblebendsalongthelinkwhichareshownwhenthetotallossofthelinkisgreaterat1550nmthanat1310nm.However,OTDRisthenrequiredtolocalizethebend.

Figure 13. Qualifying the FTTH network with a loss test set/ORL meter

Testing can be performed either at the splitter location to qualify the individual feeder and distribution cables or end-to-endbetweentheOLTandtheONT.Whenusingalosstestset/ORLmetertopinpointanissue,testingisalsorequiredusinganOTDR.JDSUrecommendsitsMTS-4000withthe4126MA1310/1550nmOTDRmoduleoritsMTS-6000withthe8126LR1310/1550nmOTDRmodule.

Loss and ORL ReferencingPerformlossandORLreferencingonbothunitsonceperdayorwhenchangingthetestjumpers.Afterperform-ingthis,donotdisconnectthejumpersfromthesourceside.

Acceptance testing with Loss test Set/ORL meter• Connectorized splitter: Link insertion loss & ORL of the feeder part at 1310/1550 nm Link insertion loss & ORL of the distribution part at 1310/1550 nm• Spliced splitter: Insertion loss & ORL between OLT and ONT at 1310/1550 nm

Central O�ce

1310 nm

1490/1550 nm

PON OLT

Video AMP

RF Video

OLT-55/ORL-55ORL/IL

OLT-55/ORL-55ORL/IL

Feeder Fiber

Drop Terminals

Passive Splitter

ONT

ONT

ONT

ONT

Distribution FibersWDM

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Loss ReferencingThe recommended and most accurate method for loss referencing is conducting the side-by-side reference measurement,placingthatthetwolosstestsetsnexttoeachotherandconnectingthemwiththerespectivejumpers (one for each unit) and a mating adapter before performing the reference steps on the unit.Ifunabletoperformtheside-by-sidereference,forexamplewhenthetwounitsarenotatthesamelocation,considerperformingtheloopbackreferenceinstead.Inthiscase,connectthejumperbetweenthesourceandthe specific power meter before performing the reference steps on the unit.

ORL ReferencingORLreferencingrequiresatwo-stepprocessforallunits.Firstconnectthesourcetothespecificpowermeterto measure the output power at the output of the jumper. Then disconnect the jumper from the specific power meter,addanon-reflectiveterminator(orperformamandrelwrap),andperformazeroORLreferencemea-surement.Removethemandrelorthenon-reflectiveterminator,butkeepthejumperattachedtotheunititself.Attheendofthereferencemeasurement,theunitwilldisplayaresultforthehighestvaluethatcanbemeasuredforthenetwork.Therefore,becarefulwhenperformingthismeasurement.AlsousinganAPCconnectorfortheunititselfishighlyrecommendedbecauseitincreasesthemeasurementrangeoftheORL.

Loss and ORL MeasurementsAftercompletingthereferencingprocess,connectthejumperstoeachendofthenetworkandperformmeasurements.,ThistoolmakesanalyzinginsertionlossandORLresultssimplewithoutrequiringfurtherexpertiseforperformingOTDRmeasurements.

Result AnalysisAfterperformingtheacquisition,comparetheresultstothoseexpectedaccordingtonetworkandcustomerstandards.NetworkproblemsrequireuseofanOTDRtotroubleshoot,identify,andlocatetheissue(s).PONnetworkscanhave1490/1550nmdownstreamand1310nmupstream,therefore,themostcriticalORLvaluestoconsiderarethe1550nmORLmeasurementsfromcentraloffice/OLTtothecustomerpremises/ONTandthe1310nmORLmeasurementfromcustomerpremises/ONTtothecentraloffice/OLT.However,conductingallORLmeasurementsinbothdirectionscansimplifytheprocess..Whenusingthelosstestset/ORLmeter,theinsertionlossvaluesintegratethelossoftheconnectorsatthebeginning and the end of the link as well as integrating the jumper connectors.ListedbelowarethemostcommonissuesfoundonPONnetworks:• Lackofcommunicationbetweenunits—Check/cleantheconnectionbetweentheunitsandthenetwork,as

wellasuseaVFLtoinvestigatewhetherabendandbreakexistsalongthepatchpaneloralongthelink.Ifso,performanOTDRmeasurementtolocatethebreakorissue.

• Distancediffersfromthatexpected,meaningthatthefibertesteddiffersfromtheexpectednumber—Check the fiber number to ensure correct fiber selection or correct continuity.

• Totallossisgreaterthanexpected—PerformanOTDRmeasurementandobservethetableofeventsforlargesplices,connectors,orbends.

• ORLisworsethantheexpected,indicatedbyasmallerORLnumber,suchas30dBwhichisworsethana40dB—PerformanOTDRmeasurementandobservethetableofeventsforbadreflectancevaluesandcheckthesectionalizedORLontheOTDRtrace.

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Typical Acceptance ValuesAcceptancevaluesoninsertionloss,ORL,anddistanceareforreferencepurposesonlyandarenotapplicabletoalltypesofnetworks.Onemustanalyzethetypeofnetworkbeforesettingtheacceptancevalues.

TheIEC-61300-3-35standarddefinesthepass/failcriteriaforconnectorinspection.Also,somePONstan-dardsprovidetherecommendationslistedinTable1forinsertionloss,ORL,anddistancelimitations.

G-PON E-PON G.982, G.983.1, G.984.2, and IEEE 802.3 G.652 Fiber Specs

Attenuation ranges Class A: 5 to 20 dB PX-10: up to 23 dB Class B: 10 to 25 dB PX-20: up to 26 dB Class C: 15 to 30 dB (Table 60-9) (Table 3/G.982) Differential optical loss 15 dB — (Table 4-a/G.983.1) Maximum split ratio 1x64 (Table 2a/G.984.2) 1x32Minimum ORL of ODN 32 dB, optionally 20 dB 20 dB (Table 2b/G.984.2) (Table 60-3)Maximum reflectance of equipment, Less than –20 dB —measured at receiver wavelength, for OLT receiver (Table 2b/G.984.2)Maximum reflectance –35 dB –26 dB (G.982 Chapter 11.4) (Chapter 60.9.3)Reach Up to 20 km PX-10: Up to 10 km Up to 60 km logical reach PX-20: Up to 20 km (Table 2a/G.984.2) (Table 60-1)Fusion splice reflectance –50 dB recommended Not defined (G.982 Chapter 11.4) Splitter loss — 1x16: 14.5 typical (Chapter 60.9.3)Connector loss — 0.5 dB per connection 0.75 dB for 2 connections (Chapter 60.9.3)Cable attenuation Example of G.652.B fiber (but other fiber types exist, 0.4 dB/km max at 1310 nm with other specs): 0.35 dB/km max at 1550 nm 0.4 dB/km max at 1310 nm (Table 60-14) 0.35 dB/km max at 1550 nm (Table 3/G.652) Concatenated cable attenuation Typical 0.5 dB/km at 1310 nm —(including typical splices and connectors) Typical 0.35 dB/km at 1550 nm (Table I.1/G652)

Table 1. Specifications and acceptance values based on ITU and IEEE standards

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Formostoftheindividualelementsofthenetwork,theITU-TG.671providestypicalindividualvaluesaswellas other typical values found in the field. However this information may vary according to equipment vendors. SospecificationandacceptancevaluescanbedefinedasshowninTable2.

Fiber Network Typical Loss Maximum Loss Typical ORL (dB) Min ORL (dB) Element (dB) (dB) (or reflectance (or reflectance when applicable) when applicable)

Fiber attenuation 0.35 dB/km at 1310 nm — 30 dB (long distance)/ 30 0.2 dB/km at 1550 nm 40 dB (150 m) at 1310 nm 30 dB (long distance)/40 dB (150 m) at 1550 nm Fusion splice 0.1 0.2 None None 0.3 (G.651) –70 (G.671)Mechanical splice 0.2 0.5 (G.651) None –50 –40 (G.671)Connector 0.5 0.7 65 (APC) –50 (APC) 0.5 (G.671) 55 (UPC) –40 (UPC) –35 (G.671)Splitter (G.671) None –55 1x2 3.5 1x2 4.2 –40 (G.671) 1x4 6.5 1x4 7.8 1x8 9.5 1x8 11.4 1x16 12.5 1x16 15 1x32 16 1x32 18.6 1x64 20 1x64 22 1x128 23 1x128 25

Table 2. Typical specifications and acceptance values

Add values when qualifying the complete network according to the various elements and wavelengths.Forexample,thenetworkhas:• 5kmoffiberonthefeederside,onefusionspliceat1.5km,andanAPCconnectoratthebeginningofthe

link• aconnectorized1x32splitterwithAPCtype• multiplelegs,oneof1kmthatisfusionsplicedat400mandanAPCconnectorattheendofthelink

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Calculating the total loss for the link described in the network above requires adding the loss of the individual elements. Table 3 provides the information to calculate the total link loss.

Fiber Network Typical Insertion Loss Calculation

Element Typical Individual Typical Cumulative Typical Individual Typical Cumulative Loss at 1310 nm (dB) Loss at 1310 nm (dB) Loss at 1550 nm (dB) Loss at 1550 nm (dB)1 connector 0.5 0.5 0.5 0.55 km of fiber 5x0.35 = 1.75 2.25 5x0.2 = 1.0 1.51 fusion splice 0.1 2.35 0.1 1.61 connector 0.5 2.85 0.5 2.11x32 splitter 16 18.85 16 18.11 connector 0.5 19.35 0.5 18.61 km of fiber 1x0.35 = 0.35 19.7 1x0.2 = 0.2 18.81 fusion splice 0.1 19.8 0.1 18.91 connector 0.5 20.3 0.5 19.4

Table 3. Total link loss calculation

Table4providestheinformationnecessarytocalculatethetotalupstreamORLat1310nm.Table5providestheinformationnecessarytocalculatethetotaldownstreamORLat1550nm.

Fiber Network 1310 nm ORL Typical Calculation Upstream (from ONT to OLT)

Typical ORL per Element Typical Cumulative at 1310 nm (dB) ORL at 1310 nm (dB)1 connector 50 501 km of fiber 40 401 fusion splice None 401 connector 50 401x32 splitter None 401 connector 50 405 km of fiber 32 401 fusion splice None 401 connector 50 40

Table 4. Total ORL calculation at 1310 nm

White Paper: Fiber Testing—The Fundamentals for Successful Broadband Deployment 19

Fiber Network 1550nm ORL Typical Calculation Downstream (from OLT to ONT)

Typical ORL per Element Typical Cumulative ORL at 1550 nm (dB) at 1550 nm (dB)1 connector 50 505 km of fiber 35 351 fusion splice None 351 connector 50 351x32 splitter None 351 connector 50 351 km of fiber 40 351 fusion splice None 351 connector 50 35

Table 5. Total ORL calculation at 1550 nm

PerforminginsertionlossandORLmeasurementsforthisspecificfiberlinkrequirescomparingthetestresultstothecumulativeinsertionlossof20.3dBandORLof40dB(fromONT)at1310nmandtheinsertionlossof19.4dBandORLof35dB(fromOLT)at1550nm.IfusinganOTDRwithoutalaunchcable,omittheconnectorlossesandORLatthebeginningandendofthelinkandcomparethetestresultstothecumulativeinsertionlossof19.3dBandORLof40dBat1310nmforexample.The report at the end of the tests will provide the following information dependent upon whether the insertion losstestsetorOTDRisused.

Usingtheinsertionlosstestset:• Insertionlossat1310/1550nm(andeventuallyat1490nm)• ORLat1310/1550nm(andeventuallyat1490nm)• Linkdistanceinformation• Commentsorissues

UsingtheOTDR:• Insertionlossat1310/1550nm• ORLat1310/1550nm• Linkdistanceinformation• Commentsorissues• Ifrequired,detailedinformationsuchas: –Distancesofallsections –LossandORLofallelementssuchassplice,connector,orsplitter –Reflectanceofallreflectiveelementssuchastheconnectors

White Paper: Fiber Testing—The Fundamentals for Successful Broadband Deployment 20

Recommended JDSU Test Tools for FTTH NetworksThis document only describes the process for FTTH network qualification before installing equipment which is the first stage of FTTH network deployment. The complete process for FTTH networks is:• qualification/fiberconstruction(noactiveequipmentinvolved)• turn-up(involvesactiveequipmentsuchasOLTsandONTs)• troubleshooting• monitoring

Eachstagerequiresspecifictesttoolsasprovidedinthefollowingsubsections.JDSUistheuniquetestequip-ment provider that offers a complete test suite that can fully qualify the network from fiber construction to network monitoring.

Qualification ToolsThe following list shows the recommended test tools for FTTH network qualification.• Opticalmicroscope:JDSUFBPprobeswithHD2/3displaysorJDSUHP3-60fiberinspectionandtest

tool.• OTDRs:JDSUT-BERD/MTS-4000with4126MA1310/1550nmOTDRmoduleorJDSUT-BERD/

MTS-6000with8126LR1310/1550nmOTDRmodule.Ifrequested,1490or1625nm/1650nmwave-lengths can also be provided.

• Losstestset/ORLmeters:JDSUOLT-55andORL-55orJDSUT-BERD/MTS-6000with8126OFI11310/1550nmlosstestset/ORLmodule.Ifrequested,1490or1625nmwavelengthscanalsobepro-vided.Theuseofthistoolmayalsorequireanopticaltalkset(ifcellphonescannotbeused).JDSUOTS-55orthetalksetoptionforJDSUMTSunitsareavailable.

• VFL:AfullrangeofJDSUsolutions,eitherstandaloneorpartoftheplatform.

Turn-up Tools

Turn-up Optical ToolsThefollowingisalistofrecommendedtesttoolsforFTTHnetworkturn-upontheopticalsideasFigure14shows.• Opticalmicroscope:JDSUFBPprobeswithHD2/3displaysorJDSUHP3-60fiberinspectionandtesttool• Standardpowermeter(incaseofpoint-to-pointnetworks)• Fiberidentifiers:JDSUFI-11/FI-10• PONpowermeter(incaseofPONnetworks)• VFL:AfullrangeofJDSUsolutions,eitherstand-aloneoraspartoftheplatform

White Paper: Fiber Testing—The Fundamentals for Successful Broadband Deployment 21

Figure 14. FTTH Network turn-up optical tools

Turn-up Service ToolsThe following is a list of recommended test tools for FTTH network turn-up on the services side.• Copper,VDSL,andtriple-playtestequipment:AfullrangeofJDSUsolutions,includingtheJDSU

T-BERD/MTS-4000withitscopper/xDSL/triple-playapplications,theJDSUSmartClassfamily,ortheJDSUHST-3000handheldservicestester

• Homewiringtestequipment:AfullrangeofJDSUsolutions,includingtheJDSUNT-950Validator,theJDSUTP-300Resi-Tester,theJDSUIVT-600,ortheHST-3000handheldservicestester

PON Equipment Turn-Up and TroubleshootingBefore activating the network or when connecting an ONT:• Optical power measurement at the OLT (1490/1550 nm) to ensure that sufficient power is delivered to the ONTs• Optical power measurement at each splitter output• Optical power measurement at the ONT (1310/1490/1550 nm)• PON selective power meter is used to troubleshoot at any point in the network

Central Office

1310 nm

1490/1550 nm

PON OLT

Video AMP

RF Video

T-BERD/MTS-4000OTDR/PON Power Meter

T-BERD/MTS-4000OTDR/PON Power Meter

T-BERD/MTS-4000OTDR/PON Power Meter

Feeder Fiber

Drop Terminals

Passive Splitter

ONT

ONT

ONT

ONT

Distribution FibersWDM

White Paper: Fiber Testing—The Fundamentals for Successful Broadband Deployment 22

Troubleshooting Tools

Optical Troubleshooting ToolsThe following is a list of recommended test tools for FTTH network troubleshooting on the optical side as Figure 15 shows.• Opticalmicroscope:JDSUFBPprobeswithHD2/3displaysorJDSUHP3-60fiberinspectionandtest

tool.• Powermeter(incaseofpoint-to-pointnetworks):JDSUOLP-35orOLP-55.• PONpowermeter(incaseofPONnetworks):JDSUOLP-57orT-BERD/MTS-4000withOLP-4057PON

meter module.• VFL:AfullrangeofJDSUsolutions,eitherstandaloneorpartoftheplatform.• OTDRs:JDSUT-BERD/MTS-4000with4126MA1310/1550nmOTDRmoduleorJDSUT-BERD/

MTS-6000with8126LR1310/1550nmOTDRmodule.Ifrequested,1490nmor1625/1650nmwave-lengths can also be provided.

• Loss test set/ORLmeters: JDSUOTS-55andORL-55or JDSUT-BERD/MTS-6000with8126OFI11310/1550nmlosstestset/ORLmodule.Ifrequested,1490or1625nmwavelengthscanalsobeprovided.Theuseofthistoolmayalsorequireanopticaltalkset(ifcellphonescannotbeused).JDSUOTS-55orthetalksetoptionofJDSUMTSunitsareavailable.

• Fiberidentifiers:JDSUFI-11/FI-10.

Figure 15. FTTH Network troubleshooting optical tools

PON Network Troubleshooting• Power level measurement with PON power meter on ONT• OTDR test from ONT or drop terminal (if a few ONTs are still responding) -> In-service OTDR (1625 or 1650 nm)• OTDR test from splitter or OLT (if no ONTs are responding)

Central O�ce

1310 nm

1490/1550 nm

PON OLT

Video AMP

RF Video

T-BERD/MTS-4000OTDR

T-BERD/MTS-4000OTDR

Feeder Fiber

Drop Terminal

Passive Splitter

ONT

ONT

ONT

ONT

Distribution FibersWDM

Drop Terminal

White Paper: Fiber Testing—The Fundamentals for Successful Broadband Deployment 23

1xn

1xn

1310 nm

1490 nm

Central O�ceServing up to 10,000 customers

Switch

In-Service OTDR

OLT

OLT

WDM

WDM

ONT

ONT

x

ONT n

ONT 1

The peak ofONT 1 ismissing

Service Troubleshooting ToolsThe following is a list of recommended test tools for FTTH network troubleshooting on the services side.• Copper,VDSL,andtriple-playtestequipment:afullrangeofJDSUsolutions,includingtheJDSU

T-BERD/MTS-4000withitscopper/xDSL/triple-playapplications,theJDSUSmartClassfamily,ortheJDSUHST-3000handheldservicestester

• Homewiringtestequipment:afullrangeofJDSUsolutions,includingtheJDSUNT-950Validator,theJDSUTP-300Resi-Tester,theJDSUIVT-600,ortheHST-3000handheldservicestester

Monitoring ToolsThe following is a list of recommended test tools for FTTH network monitoring as Figure 16 shows.• Opticallayermonitoring:JDSUONMSmonitoringsystem• Serviceslayermonitoring:JDSUNetComplete®homePerformanceManagement(PM)

Figure 16. FTTH network monitoring tools

White Paper: Fiber Testing—The Fundamentals for Successful Broadband Deployment 24

Productspecificationsanddescriptionsinthisdocumentsubjecttochangewithoutnotice.©2010JDSUniphaseCorporation301682150000810FIBERTESTFUND.WP.FOP.TM.AEAugust2010

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