
Digital Diagnostic Interface and Serial Identification
The2-wireserialinerfaceisexplicilydefinedinhe
SRev4.0.2-wireimingspecificaionsandhesruc-
ureofhememorymapareperSRev2.0.The
normal256ByeI2Caddressspaceisdividedinolower
andupperblocksof28Byes.Thelowerblockof28
Byesisalwaysdireclyavailableandisusedfordiagnos-
icinformaionprovidingheopporuniyforredicive
ailureIdenificaion,Complianceredicion,aulIsola-
ion and Componen onioring. The upper address
spaceablesareusedforlessfrequenlyaccessedfunc-
ionssuchasserialID,userwrieableEERO,reserved
EERO and diagnosics and conrol spaces for fuure
sandardsdefiniion,aswellasvagoTechnologies-spe-
cificfuncions.
Predictive Failure Identification
The diagnosic informaion allows he hos sysem o
idenifypoeniallinkproblems.Onceidenified,a“fail
over”echniquecanbeusedoisolaeandreplacesus-
pecdevicesbeforesysemupimeisimpaced.
Compliance Prediction
The real-ime diagnosic parameers can be moniored
oalerhesysemwhenoperainglimisareexceeded
andcompliancecannobeensured.sanexample,he
realimeaveragereceiveopicalpowercanbeusedo
assess he compliance of he cable plan and remoe
ransmier.
Fault Isolation
The diagnosic informaion can allow he hos o pin-
poinhelocaionofalinkproblemandacceleraesys-
emservicingandminimizedownime.
Component Monitoring
s par of hos sysem qualificaion and verificaion,
real ime ransceiver diagnosic informaion can be
combinedwihsysemlevelmonioringoensureper-
formance and operaing environmen are meeing ap-
plicaionrequiremens.
Transceiver Internal Temperature
Temperaure is measured on he BR-720DZ us-
ing sensing circuiry mouned on he inernal CB.
The measured emperaure will generally be cooler
hanlaserjuncionandwarmerhancaseandcan
be indirecly correlaed o case or laser juncion
emperaure using hermal resisance and capaciance
modeling. This measuremen can be used o observe
drifs in hermal operaing poin or o deec exreme
emperaureflucuaionssuchasafailureinhesysem
hermal conrol. or more informaion on correlaing
inernal emperaure o case or laser juncion conac
vagoTechnologies.
Transmitter Laser DC Bias Current
Laser bias curren is measured using sensing circuiry
locaedonheransmierlaserdriverIC.Normalvaria-
ionsinlaserbiascurrenareexpecedoaccommodae
he impac of changing ransceiver emperaure and
supply volage operaing poins. The BR-720DZ
usesaclosedlooplaserbiasfeedbackcircuiomainain
consanopicalpower.Thiscircuicompensaesfornor-
mal laser parameric variaions in quanum efficiency,
forward volage and lasing hreshold due o changing
ransceiveroperaingpoins.
Transmitted Average Optical Output Power
Variaions in average opical power are no expeced
under normal operaion because he BR-720DZ
uses a closed loop laser bias feedback circui o main-
ain consan opical power. This circui compensaes
fornormallaserparamericvariaionsdueochanging
ransceiver operaing poins. Only under exreme laser
bias condiions will significan drifing in ransmied
averageopicalpowerbeobservable.Thereforeiisrec-
ommendedTx average opicalpower be used for faul
isolaion,raherhanpredicivefailurepurposes.
Received Average Optical Input Power
Received average opical power measuremens are a
valuableasseforinsallersoverifycableplancompli-
ance.Drifsinaveragepowercanbeobservedfromhe
cableplanandremoeransmierforpoenialpredic-
ivefailureuse.Receivedaverageopicalpowercanbe
usedforfaulisolaion.
Auxilliary Monitors
In addiion o he parameers menioned above, 3.3V
SupplyVolage(U)isalsoreporedasauxilliarypa-
rameer.