23.03.2015 TheprinciplesoffiberopticcableinstallationCablingInstall

http://www.cablinginstall.com/articles/print/volume20/issue2/features/theprinciplesoffiberopticcableinstallation.html 1/17

TheprinciplesoffiberopticcableinstallationFebruary1,2012

FromtheFebruary,2012IssueofCablingInstallation&MaintenanceMagazine

Followingappropriatestepswillensureinstallersachievethefourgoalsofcableinstallation.

ByEricR.Pearson,PearsonTechnologiesInc.

Whenexaminingwhatmakesafiberopticnetworksuccessfulfromthestandpointsofinstallationandperformance,thecharacteristicscanbeorganizedintogroupsoffour.Asuccessfulfiberopticnetworkinstallationwillhavefourcharacteristics:1)lowopticalpowerloss,2)lowinstallationcost,3)lowtimeofinstallation,and4)highreliability.Likewise,therearefourgoalsoffiberopticcableinstallation:1)avoidbreakage,2)avoidreducedpoweratthereceiver,3)avoidreductionsinreliability,and4)proceedinasafemanner.Tomeetthesefourgoals,theinstallermustrecognizeandrespectcertainprinciples.Inthisarticle,Iorganizetheseprinciplesintofourgroups:1)environmentallimits,2)installationlimits,3)NationalElectricalCodecompliance,and4)endpreparation.

Environmentallimits

Home Theprinciplesoffiberopticcableinstallation

HOME DATACENTER

STANDARDS CABLE

CONNECTIVITY SECURITY&AV

WIRELESS DESIGNINSTALL

TEST

SUBSCRIBE|ADVERTISE

23.03.2015 TheprinciplesoffiberopticcableinstallationCablingInstall

http://www.cablinginstall.com/articles/print/volume20/issue2/features/theprinciplesoffiberopticcableinstallation.html 2/17

Thenetworkdesignerisresponsibleforspecificationofacableproperfortheintendedenvironment.Withthisdefinitionofresponsibility,theinstallermightnotneedtobeconcernedwithenvironmentlimitations.However,networkdesignersmaynotrecognizeallrelevantenvironmentalconditions.Inorderthattheinstallerrecognizeandavoidcommonfieldproblems,weprovidethisfirstprinciple:Respectenvironmentallimits

Theinstallerinstallsthecableinenvironmentalconditionsthatarewithinthelimits.Shouldthecablebeexposedtoconditionsinexcessofitslimits,thecablecanfailtoprotectthefibers.Suchfailurecanleadtofiberbreakageandexcessiveattenuationrate.

Whilenotexhaustive,thislistoffiveenvironmentalconditionsrepresentsmostoftheconditionsthathaveresultedininstallationproblems:moisture,operatingtemperaturerange,bendradii,crushloadanduseloadalongwithverticalrisedistance.

Moisture.Aninstallercaninstallacablethatisnotmoistureresistantinanenvironmentthatcontainsmoisture.Insuchacase,thecablecanchannelmoistureintoelectronics,developincreasedattenuationrateandfiberbreakageduetofrozenwater,and/orexperiencereducedfiberstrengthandbreakageduetoattackfromthechemicalsingroundwater.

Operatingtemperaturerange.Ifaninstallerinstallscableinanenvironmentwithtemperaturesoutsideofthecablesoperatingrange,thecablecanexhibitincreasedattenuationand/ordegradationofcablematerials.Intheformercase,theremaybeinsufficientpoweratthereceiverforproperlinkoperation.Inthelattercase,thefibersmaybreak.

Bendradii.Duringinstallation,theinstallercanbendacabletolessthaneithertheshorttermbendradius(20xcablediameter)orthelongtermbendradius(10xcablediameter).Inthesecases,thecablecandevelopanincreasedattenuationrate,fiberbreakageorreductioninfiberstrength.Suchasituationcanoccurinanundergroundconduitpath,inwhichtheconduitsweep,orelbow,hasaradiuslessthaneitherbendradius(20xor10x)ofthecable.Inthissituationthecablepathitsenvironmentisforcingaviolationofthebendradius.

Crushloads.Ifaninstallerinstallsacableinanenvironmentthatimposeseitheralongorshorttermcrushloadinexcessofthecableslimit,thecablecanexperienceincreasedattenuationrateandfiberbreakage.Suchasituationcanoccurwhenanindoor,tighttubecableisdirectlyburied.

Useload.Aninstallercaninstallacablewithlongterm,oruse,loadonthecableinexcessofthecablesrating.Suchaconditioncanoccurwhenthecableisinstalledbetweenwidelyspacedbuildings,widelyspacedtelephonepoles,widelyspacedpowertransmission

23.03.2015 TheprinciplesoffiberopticcableinstallationCablingInstall

http://www.cablinginstall.com/articles/print/volume20/issue2/features/theprinciplesoffiberopticcableinstallation.html 3/17

towers,andupalongverticalrise.Twoproblemscanoccurincreasedattenuationrateandfiberbreakage.

Aninstallershouldlimitthelongtermloadtoavaluelessthanorequaltothecablesrating.Todoso,theinstallerobtainstheuseloadfromthemanufacturer,typicallyfromadatasheetorfromthemanufacturerswebsite.

Theinstalleralsoshouldlimitverticalrisedistance.Theuseloadandtheverticalrisedistancearedifferentstatementsofthesamecharacteristic.Theverticalrisedistanceisthedistancetowhichthecablecanbeinstalledverticallywithoutsupport.Theinstallerlimitsthecabletoaverticaldistancelessthantheverticalriselimit.Todoso,theinstallerobtainstheverticalriselimitfromadatasheet.Theinstallercanachieveatotalverticalrisedistanceinexcessofthislimitbysupportingthecableataseparationnogreaterthanthislimit.

Indoorloosetubecablescanallowthefiberstoslideoutofthecable.Thustheinstallerinstallsserviceloopsinverticalloosetubecable.

Installationlimits

Therearetwotypesofcableinstallation:1)pullingthecableintoitspath,and2)placingthecableinitslocation.Theinstallerinstallsthecablewithconditionsthatarewithinthelimitsofthecable.Theoverallprincipleistorespectinstallationlimits.

Duringthecablepull,theinstallerrespectsfiveinstallationlimits:1)notwisting,2)installationload,3)installationbendradius,4)installationtemperaturerange,5)storagetemperaturerange.

Notwisting.Avoidanceoffiberbreakagerequiresthatfibercablesbeinstalledwithouttwisting.Inordertoavoidtwisting,theinstallerusesapullingswivelbetweenthepullingropeandthecable.Theinstallerattachesthepullropeandthecabletothepullingeye.

Inordertocomplywiththeinstallationloadlimit,theinstallermustknowtheloadlimitandhaveamethodforlimitingtheloadappliedtothecable.Theinstallerwilllearnthelimitfromthedatasheetforthecable,creatingtwoprinciples:1)Knowtheinstallationloadlimit2)Limittheinstallationload.

Therearethreemethodsbywhichaninstallercanlimittheshortterm,orinstallation,loadappliedtoacable.Inaddition,therearetwomethodsforreducingtheappliedinstallationload.

Thethreemethodshavetheadvantageofprovidingconcreteevidencethattheinstallationloadhasnotbeenexceeded.Thesemethodsaretheuseof1)apullingeyewithaswivelwithashearpin,2)apullingdevicewithaslipclutch,and3)apullingdevicewithaload

23.03.2015 TheprinciplesoffiberopticcableinstallationCablingInstall

http://www.cablinginstall.com/articles/print/volume20/issue2/features/theprinciplesoffiberopticcableinstallation.html 4/17

gage.

Theeyehasashearpin,whichisratedataloadlessthanthemaximuminstallationloadofthecable.Forexample,acablewitharatingof600poundsforcewouldrequireashearpinrated500500poundsforce.Iftheinstallerexceedstherating,theshearpin(notthecable)breaks.

Theinstallercanuseapullingeyewithaswivelwithoutashearpiniftheinstallerhassomeothermethodoflimitingtheloadappliedtothecable.Pullershavetwomethodstoprovidesuchlimitation.Thesemethodsareaslipclutchandaloadgage.

Aninstallercansettheslipclutchofapullertoalevellessthantheinstallationloadofthecable.Shouldtheappliedloadexceedthelevelset,theclutchclips,eliminatingfiberdamage.

Aninstallercansettheloadgageofapullertoalevellessthantheinstallationloadofthecable.Shouldtheappliedloadexceedthelevelset,theloadgagestopsthepullingmotorwithoutfiberbreakageordamage.Theloadgagehasanadditionaladvantageitallowsattachmentofachartrecorder,whichprovidesproofthattheinstallerdidnotloadthecableinexcessofitsrating.

Reducingtheload

Thesethreemethodslimittheloadbutdonothingtoreducetheload.Therearetwomethodsforreducingtheloadappliedtothecable:lubricantandaFigure8installation.

Theinstallerusesacablelubricanttoreducefrictionandloadonthecable.Whilecoppercablelubricantsexist,theinstallerusesafibercablelubricant,assuchalubricantismatchedtothejacketofthecable.

Thesecondmethodforreducingtheloadispullingthecablebyhandinmultiple,reducedlengthpulls.Breakingalongpullintomultiplepullsofreducedlengthreducestheloadonthecable.Iftheinstallerinstallsthecableinmultiplepulls,heorshewillstorethecableatintermediatelocationsinaFigure8pattern.Theadvantageofthismethodisreducedload.Thedisadvantageisincreasedlaborcost.

DuringaFigure8pull,theinstallerpullsthecableintothefirstmanholeandoutofasubsequentmanhole.Thesubsequentmanholemaybethenextmanholealongthecablepath,ortheNthmanholealongthecablepath.Theinstallerdeterminesthismanholebytheloadtheinstalleriswillingtoimposeonthecable.

Astheinstallerpullsthecablefromthemanhole,heorsheplacesthecableonthegroundinaFigure8pattern.Thispatterncanbe12feetlongand4to6feetwide.Forpractical

23.03.2015 TheprinciplesoffiberopticcableinstallationCablingInstall

http://www.cablinginstall.com/articles/print/volume20/issue2/features/theprinciplesoffiberopticcableinstallation.html 5/17

reasons,thepatternisrarelystackedmorethan24incheshigh.

Whentheinstallerhaspulledthecableoutofthemanhole,theinstallerandseveralhelperspickuptheFigure8andflipitoversothecableendisontop.Theinstallerputsthecablebackintothesamemanholealongthecablepath.Atthismanhole,theinstallerrepeatstheFigure8patternontheground.Theinstallercanrepeatthisprocessasmanytimesasdesired,untilthecableisinstalledalongtheentirepath.

TheinstallercanusetheFigure8methodforbothunidirectionalpulls,andmidpulls.Inamidpull,theinstallerpullsthecableinonedirection.TheinstallerplacestheremainingcableinaFigure8patternontheground.Finally,theinstallerpullsthecablefromtheFigure8patternintheoppositedirection.

Someprofessionalinstallersuseafourthmethodforlimitingtheloadtheyapplyduringinstallation.Thismethodrequirespullinga600poundforcecablebyhand.Theassumptionisthatitisessentiallyimpossibletocreatea600poundloadbyhandpullinginahorizontalaxis.Thismethoddoesnothavetheadvantageofprovidingconcreteevidencet