Fiber Characterization Characterization in Singlemode Optical Networks s s ORListhe ratio(expressedindB) of o reflectedpower toincident power froma L fiber opticsystemor alink.Thereflected power isdueto Fresnelreflectionsor n r changesinthe index of refraction. u t e R l a c i t p O
Fiber Characteriza Characterization tion Test Requirements Summary
• IEC 61300-3-6– Fiber opticinterconnectingdevices andpassive componentsBasictest andmeasurement - Part 3-6:Examinationsandmeasurements - Returnloss
OCWRMethod
OTDRMethod
Connector
Prefl
Pinc
OCWR
OTDR
This table is greatly simplified and each user must review and modify it in accordance with their specific Network Element equipment and application.
Ptrans
ORL=10log( Pinc/ Prefl)
WhymeasureORL? It isessential tomeasure backreflection wheninstallingand maintaining networksto ensureproper stability of he ht e lasersand theircentralwavelength.
Pulsed Laser Souce
LightSouce
FUT
FUT Coupler
Coupler
Termination Plug
Optical Power Meter
Optical Receiver
TheOTDRlauncheslightpulsesintothedeviceunder iceunder testandcollectsbackscatterinformationaswellas Fresnelreflections.
TheOCWRlaunchesastable,continuouswavesignal intotheopticalfiberandmeasuresthestrengthofthe time-integrated return signal.
T e st
S T M- 1 6/ O C- 4 8 1 55 0
InsertionLoss ReturnLoss (Note 1) PhysicalPlantVerification
1310/1550 nm 1550 nm 1310/1550 nm
(Incl. Connector/Splice/Point Reflectance/LocalizedLoss) SpectralAttenuation (Note 2) N o PMD ( No te 3, 3, No Not e4 e4 ) < 80 km km no not r eq uir ed u n el s s p re - 19 9 3 f bi e r CD (Note 5) 5)
TypicalValues
Notr eq equired >1 >150 km km
S T M- 1 6/ O C- 4 8 D WD M
S T M- 6 4/ O C- 1 92 1 5 5 0
S T M- 6 4/ O C- 1 92 D W D M
E q ui p me n tR e q’ d
T e ch s R e q’ d
1550/1625 nm 1550 nm 1550/1625 nm
1310/1550 nm 1550 nm 1310/1550 nm
1550/1625 nm 1550 nm 1550/1625 nm
PM & LS or OFI OFI (w/ORL option) 2 or 3 Lambda OTDR (5026 or 5036HD)
2E 1E (Note 6) 1E
1550/1625 nm <8 0k 0km no no tr equ ri ed u n el s s p re - 19 9 3 f bi e r
No P re -19 93 re req ui er d, ‘9 ‘9 3- 97 r e qu i re d i f > 50 k m , p o st ‘ 9 7 r eq ui re d >8 0 km Recommended
1550/1625 nm Pr e- 19 93 re req ui red ,‘,‘ 93- 97 r e qu i re d i f > 50 k m , p o st ‘ 9 7 r eq ui re d >8 0 km Recommended
BB Source and OSA B BS BS our ce ,O ,OS A, a n d P ol a ri z er
2E 2E
Notr eq equired >150 km
T e st i ng Recommended
Bi Bi (Note 8) Bi (Note 9)
n y i r Fibersjoinedusingsplices and a t connectorsprovoketwo typesof e m attenuation:lossandreflectance. dueessentially to o mThereareboth o Fresnelreflections. D t e c e l andreflectance? m f Whymeasureloss i connectorsare important e Splicesand componentstobetestedastheirlos n entstobetestedastheirlossesand T R reflectancesarehaving astrong impact on l thelink quality.Testscan beperformed a c duringinstallationor forcommissioning. i t p O
• IEC 61786– Calibrationof nof opticaltime-domain reflectometers(OTDR) • GR-196– GenericRequirementsfor OpticalTime DomainReflectometer (OTDR) TypeEquipment ypeEquipment • ITU-TG650.1 – Definitionsandtest methodsfor linear,deterministicattributes of singlemodefibreand cable
OTDR
Pulsed Laser Souce
TheOTDRinjectsashort,intenselaserpulseinto theopticalfiberand measuresthebackscatter andreflectionoflightasafunctionoftime.It’s thenanalyzedtodeterminethelocationofany fiberopticbreaksorsplicelosses.
FUT Coupler
Optical Receiver
Connector Pair
Fusion Splice
Connector Pair
Fiber Bend
Mechanical Splice
Fiber End
OTDR
TypicalValues Mechanicalsplice:0.4 dB Fusionsplice:0.1dB i ce:0.1dB UPCconnector:Loss:0.3dB,Refl o r:Loss:0.3dB,Reflectan e ctance:-50dB APCconnector:Loss:0.3dB,Refl o r:Loss:0.3dB,Reflectan e ctance:-65dB
Uni U ni
) B d ( n o i t a u n e t t
A
Distance(km)
4 Lambda OT OTDR( 50 5083CD)
1E (Note 7)
Uni
Requirement:-27dB Objective:-40 dB
Legend: CWDM 1E 2E Uni Bi
/ s s s s o InsertionLossisthe lossinthepower ofa o signalthatresultsfrominsertinga passive L L component(connectors,splices...) intoa continuouspath. n n o o i i t t r r WhymeasureIL? e e Ithastobetakenintoaccountin s s n transmissionsystemdesign n I I l (inputpower,receiversensitivity). a n o i t c TypicalValues Mechanicalsplice:0.4 dB e r Fusionsplice:0.1dB i ce:0.1dB i PCconnector:0.3dB o r:0.3dB d APCconnector:0.5dB o r:0.5dB i B
n PMD(oraverageDGD) iscausedby the o differentialarrivaltimeofthedifferent i polarizationmodes(horizontalandver s r tical)transmittedintoafibercausedby e itsbirefringence.PMD broadenstranscriticalforhighbit p missionpulseandis s i ratetransmission. D e d o M n orderPMDgivesthedelaycreated o Thesecond bythePMDvariationlinked tothewavelength, h, i t andthereforeisinterestingtoknowforDWDM .Secondorder PMDhastobeaddedto .Second a systems chromaticdispersion sionfigures,andthereforeis z limitingthelink distance. i r a WhymeasurePMD? l o PMD measurement shallbeat least o rmedwhenthebitrateisequalor P performedwhenthebit V
2
DGD
V
1
higher than10 Gbps.However,for some applications,suchas analogcable TV applications,lowertransmissionbit rates canbeaffectedby d by PMD.
TypicalValues Foranewfiber-MaxPMD:0.2ps/ √km
SeeNote10 Oneendedtest Twoended test (twotechnicians) Unidirectional Bidirectional
• IEC 60512-25-2–Connectorsfor electronicequipment – Testsandmeasurements - Part 25-2:Test 25bAttenuation(insertionloss) • IEC 61300-3-34– Fiberopticinterconnectingdevices andpassive components- Basictest andmeasurement • ITU-TG650.1 –Definitions andtest methodsfor linear,deterministicattributes of singlemodefibreand cable
FUT PowerMeter/ LightSource
PowerMeter/ LightSource
Insertion Losstestingistypically performedwith apower meter anda2-lambaora3-lambalight source.Automaticbi-directional testsetsobtain accurate measurementsandsavetime.
Note1: Note2:
ThisistheCW ReturnLosstest n Losstest (direct measured).Thistest issometimesnot m esnot performedandtheOTDRReturnLossvalue(calculat c ulated) e d)is accepted. Thistestis oftennotperformedprovidingthe“limits”of thespectrumtobeusedaretestedfor r umtobeusedaretestedfor insertionlosstoensur t ionlosstoensuretherewillbenoadverseeffec e therewillbenoadverseeffects frombending loss,i.e., if insertionloss istested at onewavelengthhigher thanthehighest usedwavelength,thistest may beomitted inmany cases. Note3: Theguidelinesforwhentestingisrequiredarefor r edarefor exampleonly andmayvary by application,e.g.,thetestmay beguardbandedfromtheTIArecommendationsor theuser may apply aPower Penaltytoresults greater thanthelimits specifiedby theTIA. Example:If thePMD (OC-192) is>10 psbut lessthan13ps,add1dB tothesystembudgetloss. Note4: Thistestisdynamicanditisrecommendedtoperformmultipletest t ipletestsover s overa periodof time. Note5: CD test limitsand caseswhere CD testingwould berecommendedare highly dependent onthe NetworkElement (NE) equipment specifications.Please consult your NEprovider for theselimitsand recommendations. Note6: Whilethistest isgenerallyone ended,at shortdistances,an“open”connectorat thefarend maygenerateenoughreflectancetoskew a ncetoskewtheresults.In thiscase, atechnician may apply aterminator or mandrelwrap at thefar endduringthe test. Note7: Whilethistest s testis normallyoneended,atlongerdistances,a0 dBreflector o rmay berequiredat e dat thefarendto increasedynami a sedynamicrangeofthe testset.For low iber ifber count unt testing,these sting,these may beapplied inmultiples andleft inplaceduring testing(vs. movedfrom fiber tofiber duringtesting) sothat thetest remainsone ended. Note8: Theoretica e tically,thistestonlyneedstobeperformedfromtheTransitEnd,howeverat thetimeoftest thisisoftennotwellknown.TestingORLonfiber i ngORLonfiber pairsto beused for SONETtransmissioncan leadthe user toselect thedirection pair withthe lowest ORLsfor transmitterplacement. Note9: Whilethistest s test isoneended,it isrecommendedthatit beperformedfrombothendsandtheresu m edfrombothendsandtheresultsanalyzedusingappro e dusingappropriat p riatesoftware(OF e software(OFS-100or OFS-200).Thisisnotalwaysdone. Note10: For CWDM,youcanusetherecommendedtestsfromcolumn2withoneexception.CWDM operatesfromthe1200sto1600ssoyoushoulddoyour d doyour loss testsat alower bandwidthandincrease your spectralanalysis tralanalysis test range.
e l i f o r P n o i t a u n e t t A
Attenuationistheloss ofsignalpower causedbymaterialabsorption,impurities, waveguidegeometry,andscattering.
• IEC 60793-1-40– Measurement methodsandtest procedures
FUT Broadband
Whymeasureattenuation? For DWDM systems,it isimportant toobtain thespectralattenu a lattenuationofthebandusedfor transmissi m ission,asthiswillhaveanimpacton channelequalizationas wellas amplifier specificationsif they areimplementedin the network.
10
TypicalValues
Fiber Test Products
PMD LimitsAccordingto BitRate Bit Rate Per Channel
SDH
SONET
Equivalent Timeslot
PMD Delay Limit
55 Mbps 155 Mbps 622 Mbps 1.2 Gbps 2.5 Gbps 10 Gbps 40 Gbps
N/A STM-1 STM-4 N/A STM-16 STM-64 STM-256
OC-1 OC-3 OC-12 OC-24 OC-48 OC-192 OC-768
19.3 ns 6.43 ns 1.61 ns 803 ps 401 ps 100 ps 25.12 ps
2 ns 640 ps 160 ps 80 ps 40 ps 10 ps 2.5 ps
Field PMD TestEquipment FUT Broadband Source
Polarizer
Variable Polarizer
A polarizedlightissentover theFUTand thetransmitted pectrum p s ectrum is analyzedthroughapolarizer.Theanalysisofthefixed-analyze sisofthefixed-analyzer r responseisshiftedtothetimedomainby takingtheFouriertransform. ThemeanDGDiscalculatedfrom theGaussiandistribution.
OSA
PMD Coefficient for 400 km <96 <32 <8 <4 <2 <0.25 <0.125
SpectralAttenuationtesting isperformedusingabroadband sourceand optical spectrum analyzer.TheOSA islikeawavelength-selective lective power meter.Itrecordsthe sourcespectrum(taken as reference)andcomparesit withthespectrumofthe sourceatthelinkoutput.
) m k / B d ( n o 1 i t a u n e t t A
1260nm–1360nm:0.35dB/km 1530nm–1565nm:0.22dB/km 1565nm–1625nm:0.25dB/km
• IEC 60793-1-48– Opticalfibres- Part 1-48:Measurement methodsandtest procedures- Polarizationmode dispersion • ITU-TG650.2 – Definitionsand test methodsfor statisticalandnon-linear attributesof sof singlemodefibreand cable
OSA
Source
n 0 o 0 i 0 t a 8 z D i R r E e B t c T a r / S a T h M C r e b i F
• • • • •
CompleteCWDM/DWDMtest solution OTDR,insertion loss,and power leveltesting Spectralattenuationprofile CDandPMDtesting Fullspectrum OSA
, 0 s r s 0 s e t o w n 0 L o e 2 I m n P l r e F o a i c u O t r i s e t a p s e n O I l d M a n n a , o • Automaticbi-directional measurements i L t (totallinkloss,ORL,linkdistance)and c R e powerlevel r O i • Powerlevelsupto+26dBm d • 1310,1490, 1550,1625 nmlaser sources i B
y d e l n r i a a m w a e t c f F S a r o F T S O e r l e b b a i F C l a c i t • AutomaticOTDR, DWDM,PMD, and p CDtrace analysis O • Bi-directionaland multipletrace analysis
s s r d t n t e a n , e e L m M R e d r l O u e , h s s s s d o a n L e a H n M l o r a i c e i t r w t e o p s P O n l T I R a c A i t M p S O
0 n r i e 0 a t e 1 m 5 o m S o T D t c M e e l m f i T e l R a c i t
p O
• Ideallysuited forFTTx/PON applications • Fault locator andtraffic detection • Multimode,singlemodeOTDR, andopticallosstestset
n o i s r e p s i D c i t a m o r h C
0
Thedifferent wavelengthscomposing thelight travelat different velocitiesdue tothevariationof indexofrefractionin thefiber.Limitingthetransmission speedanddistance ofthenetworks,it broadenspulse.
Distance
WhymeasureCD? CD must bemeasuredduringfiber and cablemanufacturingand alsoduringthe installationprocessto checkthe value. It’salsovery important toknow thelevel of chromaticdispersionpresent inthe networktoaddinlinemodules,suchas r ktoaddinlinemodules,suchas amplifiers,add/dropmultiplexers.. .or beforeany compensationprocess.
8 50
13 10 Wavelength(nm)
15 50
• IEC 60793-1-42– Opticalfibres- Part 1-42:Measurement methodsandtest procedures- Chromaticdispersion • ITU-TG650.1– Definitionsandtest methodsfor linear,deterministicattributes of singlemodefibreand cable CD LimitsAccordingto BitRate B ti R at e P er Chann el
S DH DH
S ON ON ET
51 Mbps 155 Mbps 622 Mbps 1.2 Gbps 2.5 Gbps 10 Gbps 40 Gbps
N/A STM-1 STM-4 N/A STM-16 STM-64 STM-256
OC-1 OC-3 OC-12 OC-24 OC-48 OC-192 OC-768
E qu vi al al en t Times ol t
19.3 ns 6.43 ns 1.61 ns 803 ps 401 ps 100 ps 25.12 ps
M ax m i um um A l ow ab ab el Time De Delay at at 1 550 nm nm
T ot al A l ow ab el D si pe pe rs rs oi n C oefficient at 155 0n 0nm foraGivenLink (NotNormalizedto1 km)
5.9 ns 1.97 ns 492 ps 246 ps 123 ps 30 ps 7.8 ps
N/A N/A N/A N/A 12000 ot 16000 ps/nm 800 ot 1000 ps/nm 60 to 100 ps/nm
40 30
FiberTypes ) m k . m n / . s p ( e u l a V D C
20
G.654Cut-off Shifted G652StandardSMF(UnshiftedDispersion) G656Non-ZeroDispersionfor WidebandTransport G655Non-ZeroDispersionShiftedSMF G653Dispersion ShiftedSMF
10 0 -10
Field CD TestEquipment
-20 -30
FUT
100
1 10 0
1 20 0
1 31 0
1 40 0 1 4 80
1 5 0 16 0
Wavelength(nm)
OTDR
1
• PowerMeters • OpticalLaser Sources • LevelAttenuators
TheOTDRsendsfour(or more)wavelengthsover ertheFUT.The timedelaybetweenthedifferentwavelengthsattheendofthe linkismeasured.Thechromaticdispersion rsionofthetestedfiber is thencalculated usingtherightnonlinearregression.
1 4
1 3
1 2
1
τ
∆τ
