• IEC 61300-3-6 – Fiber optic interconnecting devices and passive components - Basic test and measurement - Part 3-6: Examinations and measurements - Return loss

ORL is the ratio (expressed in dB) ofreflected power to incident power from afiber optic system or a link. The reflectedpower is due to Fresnel reflections orchanges in the index of refraction.

OCWR Method

The OCWR launches a stable,continuous wave signal into the optical fiber and measures the strength of thetime-integrated return signal.

Connector

Prefl PtransPinc

ORL = 10 log ( / )Pinc Prefl

OCWR

Coupler

Light Souce

OpticalPower Meter

FUT

TerminationPlug

The OTDR launches light pulses into the device undertest and collects backscatter information as well asFresnel reflections.

OTDR Method

OTDR

Coupler

PulsedLaser Souce

OpticalReceiver

FUT

Op

tica

l Re

turn

Lo

ss

Why measure ORL?Why measure ORL?It is essential to measure backreflection when installing and maintaining networks to ensure proper stability of thelasers and their central wavelength.

Typical ValuesTypical ValuesRequirement: -27 dBObjective: -40 dB

Power Meter/Light Source

Power Meter/Light Source

FUT

• IEC 60512-25-2 – Connectors for electronic equipment – Tests and measurements - Part 25-2: Test 25b- Attenuation (insertion loss)

• IEC 61300-3-34 – Fiber optic interconnecting devices and passive components - Basic test and measurement• ITU-T G650.1 – Definitions and test methods for linear, deterministic attributes of singlemode fibre and cable

Insertion Loss testing is typicallyperformed with a power meterand a 2-lamba or a 3-lamba lightsource.Automatic bi-directionaltest sets obtain accurate measurements and save time.

Insertion Loss is the loss in the power of asignal that results from inserting a passivecomponent (connectors, splices. . .) into acontinuous path.

Inse

rtio

n L

oss

/B

i-d

ire

ctio

na

l In

sert

ion

Lo

ss

Why measure IL?Why measure IL?It has to be taken into account in transmission system design (input power, receiver sensitivity).

Typical ValuesTypical ValuesMechanical splice: 0.4 dBFusion splice: 0.1 dBPC connector: 0.3 dBAPC connector: 0.5 dB

• IEC 60793-1-48 – Optical fibres - Part 1-48: Measurement methods and test procedures - Polarization mode dispersion

• ITU-T G650.2 – Definitions and test methods for statistical and non-linear attributes of singlemode fibre and cable

A polarized light is sent over the FUT and the transmitted spectrum isanalyzed through a polarizer.The analysis of the fixed-analyzerresponse is shifted to the time domain by taking the Fourier transform.The mean DGD is calculated from the Gaussian distribution.

PMD (or average DGD) is caused by thedifferential arrival time of the differentpolarization modes (horizontal and ver-tical) transmitted into a fiber caused byits birefringence. PMD broadens trans-mission pulse and is critical for high bitrate transmission.

Polarizer OSAVariablePolarizer

BroadbandSource

FUT

PMD Limits According to Bit Rate

Field PMD Test Equipment

DGD

V1

V2

The second order PMD gives the delay createdby the PMD variation linked to the wavelength,and therefore is interesting to know for DWDM systems.Second order PMD has to be added tochromatic dispersion figures,and therefore is limiting the link distance.

Po

lari

zati

on

Mo

de

Dis

pe

rsio

n

Why measure PMD?Why measure PMD?PMD measurement shall be at least performed when the bit rate is equal orhigher than 10 Gbps. However, for someapplications, such as analog cable TVapplications, lower transmission bit ratescan be affected by PMD.

Typical ValuesTypical ValuesFor a new fiber - Max PMD: 0.2 ps/√km

Bit Rate SDH SONET Equivalent PMD PMD CoefficientPer Channel Timeslot Delay Limit for 400 km

55 Mbps N/A OC-1 19.3 ns 2 ns <96155 Mbps STM-1 OC-3 6.43 ns 640 ps <32622 Mbps STM-4 OC-12 1.61 ns 160 ps <81.2 Gbps N/A OC-24 803 ps 80 ps <42.5 Gbps STM-16 OC-48 401 ps 40 ps <210 Gbps STM-64 OC-192 100 ps 10 ps <0.2540 Gbps STM-256 OC-768 25.12 ps 2.5 ps <0.125

Fibers joined using splices and connectors provoke two types ofattenuation: loss and reflectance.There are both due essentially to Fresnel reflections.

Op

tica

l Tim

e D

om

ain

R

efl

ect

om

etr

y

• IEC 61786 – Calibration of optical time-domain reflectometers (OTDR)• GR-196 – Generic Requirements for Optical Time Domain Reflectometer (OTDR) Type Equipment• ITU-T G650.1 – Definitions and test methods for linear, deterministic attributes of singlemode fibre and cable

The OTDR injects a short,intense laser pulse intothe optical fiber and measures the backscatterand reflection of light as a function of time.It’sthen analyzed to determine the location of anyfiber optic breaks or splice losses.

OTDR

Connector Pair

FusionSplice

Connector Pair

FiberBend

MechanicalSplice

FiberEnd

Atte

nuat

ion

(dB)

Distance (km)

OTDR

Coupler

PulsedLaser Souce

OpticalReceiver

FUT

Splices and connectors are important components to be tested as their losses andreflectances are having a strong impact onthe link quality. Tests can be performed during installation or for commissioning.

Typical ValuesTypical ValuesMechanical splice: 0.4 dBFusion splice: 0.1 dBUPC connector: Loss: 0.3 dB, Reflectance: -50 dBAPC connector: Loss: 0.3 dB, Reflectance: -65 dB

Why measure loss and reflectance?Why measure loss and reflectance?

• IEC 60793-1-40 – Measurement methods and test procedures

Spectral Attenuation testingis performed using a broad-band source and opticalspectrum analyzer.The OSAis like a wavelength-selectivepower meter.It records thesource spectrum (taken asreference) and compares itwith the spectrum of thesource at the link output.

Attenuation is the loss of signal powercaused by material absorption, impurities,waveguide geometry, and scattering.

Wavelength (nm)

Atte

nuat

ion

(dB/

km)

0

1

10

850 1310 1550

BroadbandSource

FUT

OSA

Att

en

ua

tio

n P

rofi

le

Why measure attenuation?

Typical ValuesTypical Values1260 nm – 1360 nm: 0.35 dB/km1530 nm – 1565 nm: 0.22 dB/km1565 nm – 1625 nm: 0.25 dB/km

Why measure attenuation?For DWDM systems, it is important to obtainthe spectral attenuation of the band used fortransmission, as this will have an impact onchannel equalization as well as amplifierspecifications if they are implemented in the network.

Fiber Characterization in Singlemode Optical Networks

Fiber CharacterizationTest Requirements Summary

This table is greatly simplified and each user must review and modify it in accordance with their specific Network Element equipment and application.

Note 1: This is the CW Return Loss test (direct measured). This test is sometimes not performed and the OTDR Return Loss value (calculated) is accepted.Note 2: This test is often not performed providing the “limits” of the spectrum to be used are tested for insertion loss to ensure there will be no adverse effects

from bending loss, i.e., if insertion loss is tested at one wavelength higher than the highest used wavelength, this test may be omitted in many cases.Note 3: The guidelines for when testing is required are for example only and may vary by application, e.g., the test may be guardbanded from the TIA recom-

mendations or the user may apply a Power Penalty to results greater than the limits specified by the TIA. Example: If the PMD (OC-192) is >10 ps but less than 13 ps, add 1 dB to the system budget loss.

Note 4: This test is dynamic and it is recommended to perform multiple tests over a period of time.Note 5: CD test limits and cases where CD testing would be recommended are highly dependent on the Network Element (NE) equipment specifications. Please

consult your NE provider for these limits and recommendations.Note 6: While this test is generally one ended, at short distances, an “open” connector at the far end may generate enough reflectance to skew the results. In

this case, a technician may apply a terminator or mandrel wrap at the far end during the test.Note 7: While this test is normally one ended, at longer distances, a 0 dB reflector may be required at the far end to increase dynamic range of the test set. For

low fiber count testing, these may be applied in multiples and left in place during testing (vs. moved from fiber to fiber during testing) so that the test remains one ended.

Note 8: Theoretically, this test only needs to be performed from the Transit End, however at the time of test this is often not well known. Testing ORL on fiber pairs to be used for SONET transmission can lead the user to select the direction pair with the lowest ORLs for transmitter placement.

Note 9: While this test is one ended, it is recommended that it be performed from both ends and the results analyzed using appropriate software (OFS-100 or OFS-200). This is not always done.

Note 10: For CWDM, you can use the recommended tests from column 2 with one exception. CWDM operates from the 1200s to 1600s so you should do your loss tests at a lower bandwidth and increase your spectral analysis test range.

Legend:CWDM See Note 101E One ended test2E Two ended test (two technicians)Uni UnidirectionalBi Bidirectional

Test STM-16/OC-48 1550 STM-16/OC-48 DWDM STM-64/OC-192 1550 STM-64/OC-192 DWDM Equipment Req’d Techs Req’d Testing Recommended

Insertion Loss 1310/1550 nm 1550/1625 nm 1310/1550 nm 1550/1625 nm PM & LS or OFI 2E BiReturn Loss (Note 1) 1550 nm 1550 nm 1550 nm 1550 nm OFI (w/ORL option) 1E (Note 6) Bi (Note 8)Physical Plant Verification 1310/1550 nm 1550/1625 nm 1310/1550 nm 1550/1625 nm 2 or 3 Lambda 1E Bi (Note 9)(Incl. Connector/Splice/Point OTDR (5026 or 5036HD) Reflectance/Localized Loss)Spectral Attenuation (Note 2) No 1550/1625 nm No 1550/1625 nm BB Source and OSA 2E UniPMD (Note 3, Note 4) <80 km not required <80 km not required Pre-1993 required, ‘93-97 Pre-1993 required, ‘93-97 BB Source, OSA, 2E Uni

unless pre-1993 fiber unless pre-1993 fiber required if >50 km, post ‘97 required if >50 km, post ‘97 and Polarizerrequired >80 km required >80 km

CD (Note 5) Not required >150 km Not required >150 km Recommended Recommended 4 Lambda OTDR (5083CD) 1E (Note 7) Uni

Note: Specifications, terms and conditions are subject to change without notice.

30137200 000 1005 FIBERCHAR.PO.FOP.TM.AE To learn more, visit jdsu.com/fiberoptictest

• Complete CWDM/DWDM test solution• OTDR, insertion loss, and power level testing• Spectral attenuation profile• CD and PMD testing• Full spectrum OSA

Fib

er

Ch

ara

cte

riza

tio

nM

TS

/T-B

ER

D 8

00

0

Fiber Test Products

• Ideally suited for FTTx/PON applications• Fault locator and traffic detection• Multimode, singlemode OTDR,

and optical loss test set

Op

tica

l Tim

e D

om

ain

Re

fle

cto

me

ter

MT

S-5

10

0

• Automatic OTDR, DWDM, PMD, and CD trace analysis

• Bi-directional and multiple trace analysisOp

tica

l Fib

er

Tra

ce a

nd

Ca

ble

So

ftw

are

OF

S F

am

ily

• Power Meters• Optical Laser Sources• Level AttenuatorsIn

sert

ion

Lo

ss,O

RL,

an

dO

pti

cal P

ow

er

Me

ass

ure

me

nts

SM

AR

T O

pti

cal H

an

dh

eld

Me

ters

• IEC 60793-1-42 – Optical fibres - Part 1-42: Measurement methods and test procedures - Chromatic dispersion• ITU-T G650.1 – Definitions and test methods for linear, deterministic attributes of singlemode fibre and cable

The OTDR sends four (or more) wavelengths over the FUT.Thetime delay between the different wavelengths at the end of thelink is measured.The chromatic dispersion of the tested fiber isthen calculated using the right nonlinear regression.

The different wavelengths composingthe light travel at different velocities dueto the variation of index of refraction inthe fiber. Limiting the transmissionspeed and distance of the networks, itbroadens pulse.

CD Limits According to Bit Rate

Field CD Test Equipment

Distance

Fiber Types

1 41 3

1 21 1

τ

∆τ

OTDR

FUT

Ch

rom

ati

c D

isp

ers

ion

Why measure CD?Why measure CD?CD must be measured during fiber andcable manufacturing and also during theinstallation process to check the value.It’s also very important to know the levelof chromatic dispersion present in thenetwork to add in line modules, such asamplifiers, add/drop multiplexers. . . orbefore any compensation process.

Bit Rate SDH SONET Equivalent Maximum Allowable Total Allowable DispersionPer Channel Timeslot Time Delay at 1550 nm Coefficient at 1550 nm

for a Given Link (Not Normalized to 1 km)

51 Mbps N/A OC-1 19.3 ns 5.9 ns N/A155 Mbps STM-1 OC-3 6.43 ns 1.97 ns N/A622 Mbps STM-4 OC-12 1.61 ns 492 ps N/A1.2 Gbps N/A OC-24 803 ps 246 ps N/A2.5 Gbps STM-16 OC-48 401 ps 123 ps 12000 to 16000 ps/nm10 Gbps STM-64 OC-192 100 ps 30 ps 800 to 1000 ps/nm40 Gbps STM-256 OC-768 25.12 ps 7.8 ps 60 to 100 ps/nm

CD V

alue

(ps.

/nm

.km

)

Wavelength (nm)

-30

-20

-10

0

10

20

30

40

1000 1100 1200 1310 1400 1480 1550 1600

G.654 Cut-off ShiftedG652 Standard SMF (Unshifted Dispersion)G656 Non-Zero Dispersion for Wideband TransportG655 Non-Zero Dispersion Shifted SMFG653 Dispersion Shifted SMF

• Automatic bi-directional measurements (total link loss, ORL, link distance) and power level

• Power levels up to +26 dBm• 1310, 1490, 1550, 1625 nm laser sources

Bi-

dir

ect

ion

al I

nse

rtio

n L

oss

,O

RL,

an

d O

pti

cal P

ow

er

Me

asu

rem

en

tsO

FI-

20

00