Optical Fiber Test
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1OpticalFiberTesting2ContentsTheOpticalTime-DomainReflectometer(OTDR)Thelengthmeasurements:generalprocedureProcedureformeasurementofRE+3/1/xandRE-4/1/xfibersProcedureformeasurementofCables2and3ConnectingfiberstothepatchpanelTestingaftertheconnectionShippingthepatchpaneltoP5SummaryofOTDRtestsperformedsofarNextsteps3TheOpticalTime-DomainReflectometer(OTDR)ThemanualdescribesguidelinesonhowtoconnectandcleanfibersinordertoensuretheOTDRissafeTheOTDRisdesignedforshort-range(10-100’smetersinorderofmagnitude)Itsphoton-countingtechnologyallowsmeasurementsofdistributedattenuationandhomogeneityofthefiberThelatercanhelpidentifydamagesthatmayoccurduringthelayingoutofthefiberOperationissimple:plugstraighttipconnector(STP)intothefiberarray,connectOTDRusbcableintoaPCandpower-uptheOTDR4TheOTDR:Principleofphoton-countingTheOTDRsendsshortlightpulsestowardstheFiberUnderTest(FUT)andbackreflectedlightisanalysed.Highresolution(approx10cm)demandsshortpulses(approx1ns)andlowenergylevels.Photon-countingisasolutiontobothconditions.TheOTDRfillsahistogramforback-reflectionbycountingphotonsAndreswastoldbyanexpertthatastandardSTPisusedfor400OTDRtest.Wehaveusedour“poorman”versionofaSTPforaround2300tests.5TheOTDR:back-reflectionmeasurementCalculatingreflectanceinanOTDRisacomplicatedprocessinvolvingthebaselineoftheOTDR,backscatterlevelandpowerinthereflectedpeakasshowninthediagrambelow.Sincereflectanceisdefinedasafractionofthepowerinthetestsignal,theOTDRmustcalculatethetestpowerfromthebackscatterlevelofthefiber,basedonthetypicalbackscattercoefficientofthefiberbeingtested.ButthisisdoneautomaticallybytheOTDRsoftwarehttp://www.thefoa.org/tech/ref/testing/test/reflectance.html6Thelengthmeasurements:generalprocedureTheamountoflightreflectedatajointbetweentwofibersisdeterminedbyelectromagneticprocesses.Connectorsproducereflectancepeaks,higherpeaksindicatehigherreflectance.ThepositionofeachvisiblepeakiscomputedbytheOTDRsoftware.Weidentifytheconnectorssurroundingafiberofinterestandreadtheirdifference.Thisdifferenceisthelengthofthecable.Technicaldetailsofthemeasurementonthemanualthatcanbeconsultedonline:http://www.ttswebsite.com/manuals/otdr_distance.pdf7ProcedureformeasurementofRE+3andRE-4Cablesweregiveninboxescontaining8intotal.WeconnectedtheminseriesintotheOTDRasshownbythehappypersononthepicture.Anorangecableisusedasstraighttipconnector(STP)tojointheOTDRtotheseries.AbluecableisusedtoendtheseriesEveryconnectionwascleanedappropriatelybeforetesting8ProcedureformeasurementofRE+3andRE-4Resultsofthemeasurement:thesoftware’sdefaultsettingsshowedfluctuations(leftscreenshot)thatdidnotallowanunderstandingoftheresults.Differentsamplingaveragesweretested(middleandrightfigures).Theaveragewiththebestpositionresolutionwasselectedempirically(middlefig.)fortherestofthemeasurements.The10cables(8fortesting,inputandoutput)canbeseenintheresultingscreen.9ProcedureformeasurementofCable2and3Cables2and3areasymmetric:ononeendtheyhave12x12opticalconnectorssortedbycolor(canbeseenatthebottomofthepicture)ontheotherendtheyhavea6cableseachwith24small(nmradius)outputs(canbeseeninthemiddleofthepicture)10ProcedureformeasurementofCable2and3ThemapofthecolorstothenumberofthecableconnectorisshowninthefigureEachconnectionwascleanedastheOTDRmanualdemandsThefirsttestwasperformedwithaserieswithoneofeachcableThe2ndtestwasperformedwith2cablesofeachinseries11ProcedureformeasurementofCable2and312CorrugatedPipeAfterthetests,opticalfiberforthepatch-panelwasprotectedwithcorrugatedpipesAfterthecableswereprotectedtheyweretestedagain,inordertocheckthattheproceduredidnotdamagethefibers13Connectingthefiberstothepatch-panelTheprotectedfiberswillbeinstalledinP5soon(thiswaswrittenonJune18)Theywillbeinstalledinaboxwecallpatch-panelTheconnectionwasperformedbymycolleagueGabrielArtemioAyalaSanchez14ShippingpatchpaneltoP5AftertheconnectionprocedurefiberswerearrangedinawoodtableinordertofacilitateitstransporttoP5Afterthearrangementwasdone,thefibersweretestedoncemorewiththeOTDR.Finally,onJune14at10amthepatch-panelsetupwasretrievedfrom904andsenttoP515SummaryofOTDRtestsperformedsofar7May-288RE314May-C2,C316May-28820May-(next)21May-RE422May-28823May-288C2/324May-96RE327May-168RE3--Corrugatedtest--28May-24RE431May-12C41June-12C43June-96C44June-24C45June-108C4--TestonPanel--6June-24RE411June-96RE3/4C2/212June-184RE3/4C2/213June-128RE3/4C2/214June-160RE3/4C2/2Totaltests=230816NextstepsThesummaryandthedatafilesproducedbytheOTDRforallthetestsisavailableatCERNboxasacompresseddocument:https://cernbox.cern.ch/index.php/s/Gh3mq3M5ZQycp65Thepatch-panelfortheotherendcapmustbesetupandsendtoP5urgently
OpticalFiberTestingContentsTheOpticalTime-DomainReflectometer(OTDR)Thelengthmeasurements:generalprocedureProcedureformeasurementofRE+3/1/xandRE-4/1/xfibersProcedureformeasurementofCables2and3ConnectingfiberstothepatchpanelTestingaftertheconnectionShippingthepatchpaneltoP5SummaryofOTDRtestsperformedsofarNextstepsTheOpticalTime-DomainReflectometer(OTDR)ThemanualdescribesguidelinesonhowtoconnectandcleanfibersinordertoensuretheOTDRissafeTheOTDRisdesignedforshort-range(10-100’smetersinorderofmagnitude)Itsphoton-countingtechnologyallowsmeasurementsofdistributedattenuationandhomogeneityofthefiberThelatercanhelpidentifydamagesthatmayoccurduringthelayingoutofthefiberOperationissimple:plugstraighttipconnector(STP)intothefiberarray,connectOTDRusbcableintoaPCandpower-uptheOTDRTheOTDR:Principleofphoton-countingTheOTDRsendsshortlightpulsestowardstheFiberUnderTest(FUT)andbackreflectedlightisanalysed.Highresolution(approx10cm)demandsshortpulses(approx1ns)andlowenergylevels.Photon-countingisasolutiontobothconditions.TheOTDRfillsahistogramforback-reflectionbycountingphotonsAndreswastoldbyanexpertthatastandardSTPisusedfor400OTDRtest.Wehaveusedour“poorman”versionofaSTPforaround2300tests.
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