Calrec BRIO 36 Installation Manual - page 42
42 BRIO 36
Audio Production System with Optional Networking
Connection Information
FIBRE - GENERAL RULES
Testing/Certification
Calrecstronglyrecommendsthatallfibres
areproperlytestedorcertifiedpriorto
on-sitecommissioningofthesystem.
Acertainamountofsignallossoccurs
overthelengthofafibrepath.Ifthetotal
lossofapathexceedstheopticalpower
budgetoftheSFPsinuse,thesystemwill
beunreliable.
AreasofLoss
Signallossoccursinvariousareas.Splice
lossoccursinterminations—atthepoint
wherethefibremeetstheconnector.
TypicallysplicelossshouldbedB
pertermination.Poorterminationresultsin
higherloss.
Connectorlossoccursatthepointwhere
theconnectormeetstheSFP/optical
transceiver,orotherconnectors,such
asextensioninterconnectsorpatch-
points.Connectorlossshouldtypicallybe
dBperinterconnect.Dustorother
contaminationbetweeninterconnects
orscratchesontheendsurfacecontact
pointofthefibrewillsubstantiallyincrease
theamountofloss.Assuch,dustcovers
shouldalwaysbefittedtoopticalSFPs
whennofibreisconnected,andtofibre
connectorsthatarenotlanded.
Aswellasspliceandconnectorloss,the
fibreitselfhasinherentlossoverdistance,
typicallyfibrelosswillvaryfrom3.5dB
perkmformultimodedownto0.4dB
perkmforsinglemode.Poorinstallation
practiseandlackofcarecandamagethe
fibreandresultinsubstantiallyincreased
losses.
FibreHandlingPractise
Itisimportanttofollowthefibre
manufacturer’sguidelineswhenhandling
fibreandinstallingfibreruns.Someofthe
mainpointsofconcernare:
• Minimumbendradii—fibreshouldnot
bebentthroughtootightanangle.
Tightanglescancausesignificant
lossesandpermanentdamagetothe
fibre.Fibresmaypassinitialinstallation
testingbutcanfailatalaterdatedue
tostressesonthecoreofthefibre
causedbytightbends.
• Twists,snagsandkinks—Twistsinfibre
runsaddstressestothecorewhich
cancausedamageovertime.Avoid
snaggingonothercablesorconduit
whichwillcauseexcessivetensions
whenpullingandcancausekinksand
excessivebendsinthefibre.When
routingthroughangledconduit,provide
enoughclearancearoundcornersto
avoidthefibresbeingpulledsharply
aroundtheinsideoftheangle.
• Pulling—observethemanufacturers
maximumpullingtensionspecification.
Usepullingtoolsandlubrication
whereappropriate.Neverpullonthe
connector.
• Strainrelief—fibresshouldhave
adequatestrainrelieftoprevent
tensiononterminations,howeveruseof
plasticcabletiescancrushtheinternal
constructionofthecable.Hook-and-
loop‘Velcro’strapsarehardertoover-
tightenandoffermoregentlesupport
andagreatersurfaceareatodissipate
thepressure.
• Crushing—neverplaceheavyitemson
topofunprotectedfibre.
RuggedisedFibre
Temporary/re-usablefibreruns,orruns
unprotectedbyconduitandlikelytobe
exposedtotheelements,snaggingor
tobeingstoodon,shouldalwaysbeofa
ruggedised/armouredtypetoprotectthe
internalconstructionofthecore.
CleaningandPreventative
Maintenance
Contaminationoftransceiverandfibre
matingcontactpointscausessignalloss
andcancausepermanentdamageby
scratching.
Dustcoversshouldbefittedtoallfibre
connectorsandSFPopticaltransceivers
whentheyarenotmated.Itisalso
importanttoensurethatdustcovers
themselvesarekeptclean.
Whenhandlingfibreswithoutdustcovers,
donotallowtheendstocomeintocontact
withanysurface.
Specialistmaterialsshouldbeusedfor
thecleaningofmatingcontactpointsto
avoidfurthercontaminationorscratching.
Thefollowingitemsarelowcostand
readilyavailablefromcamerashopsand
laboratorysuppliers:
• Cannedcompressedair—itisimportant
tousespecialistfiltered,clean,dryair,
freeofcontaminantsandmoisture.
• Isopropylalcohol—Usewithcotton
swabsorlint-freewipestoensureno
residueisleft.
• Lintfreewipes/longfibre,lowashlens
paper—needstobefreefromchemical
additives.
• Ensurewipesandswabsarestored
inacleanenvironmentandarenot
reused.