2.7 Testing Fibre for Next Gen Apps

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Testing Fibre for

Next Generation Applications

Adrian Young

28

th

November 2012Republic Polytechnic -Singapore

Version 1.3



Aims of this session

• Update on the impact of Encircled Flux

requirements for multimode fibre links

• 40GBASE-SR4 and 100GBASE-SR10 will only

use MPO/MTP, are you ready?

• Fibre standards update



Same Test Reference Cords

Different Result?

• This is caused by the launch condition at the sources

Multimode Source 1

Multimode Source 2



Coupled Power Ratio

• ANSI/TIA-526-14A

– Was considered to be a good way to control the launch

– Has high variability

– Three step process for each wavelength (850/1300 nm)

1. Use a 50 µm cord to maker a power measurement



Coupled Power Ratio

2. Insert a singlemode cord and record the received

power again

3. The difference in power received defines the

category of light source (850 nm example below)

30 mm loop acts as

a mode filter

TIA requirement for multimode



Encircled Flux

• EF is a multimode launch condition metric that has several purposes.

– The main intention is to reduce link loss variation when using different

light sources so that test results are similar, independent of the supplier.

• This variation has been limited to +/-10 % for link loss higher than 1 dB.

• EF was developed to keep up with components used in high speed

networks (e.g. 10/40/100 GbE).

• It was not until high speed transmission over multimode fibre became

a reality that EF measurements became important where tenths of a

dB could mean the difference between PASS and FAIL



Calibration

• Power Meters are calibrated

• Sources are NOT calibrated for launch conditions

• We need to control the launch condition for multimode sources

• This is Encircled Flux

Optical Power

intensity at each

increment of radius r

Total Power

Intensity in radius

R



Practical Considerations

of Encircled Flux Compliance

• Can I make an existing source EF compliant?

Solves the problem by controlling the number of

mode groups launched from the test cord.

Consistency in launching repeatable mode groups is

both an optical and geometric problem and is

related to the launch wavelength, the initial launchcondition (i.e., overfilled launch, or “OFL”), the test

cord fibre core size, the fibre numerical aperture,

the external mandrel, and other fibre properties.





• Can I use a VCSEL source now?

LED – incoherent light

VCSEL – coherent light, the coherence length will

cause instability in measurements if not modulated

with a random signal





• Simply make a source that is EF compliant?

EF Compliance is met at the

end of the Test Reference Cord

A Test Reference Cord will alter the EF template





• Today’s solution

• When that LC connector breaks or

wears out, it cannot be re-terminated

in the field

• Re-terminations need to be

verified for EF compliance



• Can I add a sacrificial cord to protect that LC?

• Adapter concentricity is not good enough

• Fibre core would have to be ±0.5 µm for the

sacrificial cord

• Might get close if fibre properties are similar



Sacrificial cord



Encircled Flux Compliance

• ANSI/TIA-568-C.0 refers users to

– ANSI/TIA-526-14-B for specifics

• ISO/IEC 11801:2010 refers users to

– ISO/IEC 14763-3 which refers users to

– IEC 61280-4-1 (same as ANSI/TIA-526-14-B)

• Due to vocal concerns within TIA, TSB-4979 Practical

Considerations for Implementation of MultimodeLaunch Conditions in the Field is in the works to explainthe options for customers



BICSI Singapore 2011

• If you were here you saw my presentation on how totest MPO/MTP links correctly using break out cables

• You have other options

• Polarity is often confusing – let’s take a look



Connect to MTP/MPO trunk cable

Excluded from measurementas they were referenced out

The fibre loss in the fan-out kit is negligible

Starts here Ends here

Is your measurement good? Yes, because we know

our test reference cords were good.

It does rely on good fan-out kits/cassettes.

Option 1 for testing MPO/MTP trunk cables



Move to the next pair, run an AUTOTEST

Starts here


The fibre loss in the fan-out kit is negligible

Ends here

Is your measurement good? Yes, because we know

our test reference cords were good.

It does rely on good fan-out kits/cassettes.



Connectivity Method A

• Mixed patch cord types

• Reported polarity is Type B

• Transmit-to-Receive



Connectivity Method B





Connectivity Method C

• Mixed patch cord types





Will you test the factory terminated

MPO/MTPs once installed?

• “It’s already tested at the factory, so no”

• The Fluke Networks’ Technical Assistance Center has

seen calls where the field testing is not PASSing theirspecification

– Damaged in transit

– Damaged during install



Setting a reference

• No different to a normal source/meter

Pinned Pinned


Type B Cord



The measurement

• Disconnect from the meter




The measurement

• Insert a known good cord into the meter




The measurement

• Connect to the trunk cable




The measurement





The measurement





Example test result #1

• Expect the values to vary across the fibres





Fibre #3 is out of spec





Fibre #1 is broken



ISO/IEC 14763-3

• Update in progress

– Test reference cord length minimum increases to 2 m from

1 m since singlemode fibre can remain bimodal up to 2 m

– Battle over 1 jumper vs. 3 jumper continues, even though

it is clear that the 1 jumper method offers superior

measurement uncertainty

– Measurement uncertainty formulae may be included for

users to calculate (or an example)



ISO/IEC 14763-3

• Measurement uncertainty calculation

• Common error is to look at Power Meter Accuracy• The Power Meter Uncertainty is an absolute measurement

• The Insertion Loss measurement is a relativemeasurement



ANSI/TIA-568-D

• Work continues on updating the ANSI/TIA-568-C series

• The TR42 Group believes that 568-D.3 should be modeled after

568-C.2

• For example, fibre testing information would be transferred from

568-C.0 to 568-D.3 or 568-D.0 would refer to ANSI/TIA-526-14-B

and ANSI/TIA-526-7-B.

• Expect it to include the TSBs created since the introduction of theC Series as well as the multiple addendums

• My guess, edited versions by June 2013, balloting by October

2013 & publication by October 2014.



ANSI/TIA connector loss

• Currently 0.75 dB

• Does not fully support 40GBASE-SR4 or 100GBASE-SR10

• IEEE requirement is 1.5 dB @ 150 m

• The group is still looking to update the requirement inTIA, work continues so watch this space

0.75 dB 0.75 dB150 m OM4

(0.36 dB)

Total loss = 1.86 dB



ANSI/TIA-942-A

• Telecommunications Infrastructure Standard for Data

Centres

– Published August 2, 2012

– Harmonized with ANSI/TIA-568-C.0

– Recognizes LC as the connector choice for simplex or

duplex connections

– Recognizes MPO/MTP for more than two fibres – Cable minimum is now OM3/OM4 – OM1/OM2 are

no longer recognized as supported

– Cat 3/5e no longer recognized as supported



10GBASE-SR over OM4

• IEEE 802.3ae was written before OM4

• IEEE maintenance task group asked to update

• 10GBASE-SR over OM4 is now supported up to 400 m

with a total loss of 2.9 dB

• ANSI/TIA-568-C.0-3 addendum matches IEEE

• 400 m is based on a spectral width of 0.65 nm – Some argue devices are around 0.47 nm

– Therefore you can go 500 m or further

– Proceed with caution, talk to your vendors



Summary

• Encircled Flux will showing up on specifications

• Keep and eye out for TIA TSB-4979 for guidance on EF

• Explore your options for testing MPO/MTP links

– Make sure you understand polarity

– Are you able to test for polarity and document it?

• TIA will have to issue guidance on current 0.75 dBconnector limit



Thank you for your time

Adrian Younge-mail: harry.potter @flukenetworks.com

Documents

2.7 Testing Fibre for Next Gen Apps