Fiber Installation

Simplifying the Complexity of Fiber Certification

Eric Lie, PsiberData

Standards: What’s Hot Encircled Flux Standard in Multimode testing

The new ISO standards has EF compliance as a normative requirement Enforcing the standard in the field Qualifying/maintaining light sources for EF compliance in the field

The new IEC 14763-3 Standard

TIA and ISO/IEC14763-3 standard provide significantly different limit budgets Application limits different from Premise limits and Link Vs Channel Testing Uncertainty in measurements

Negative Loss Measurements

Test usually shown as a pass in the tester but results not meaningful to end-user Standards should enforce a failure result if the negative loss is greater than uncertainty

MPO/MTP Testing

With the limits getting tighter for 10GbE and 40GbE uncertainty plays significant part in pass/fail decision

How do you calculate loss/budget?

Encircled Flux Standard in Multimode testing Encircled Flux: What you need to know

EF Basics: What does it mean

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Pixels along x-axis Pixels along y-axis Position of pixels

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Output of CCD (Red to blue transition indicates intensity distribution)

Measurement Setup

Calculated EF template

um (Core of MM Fiber)

VCSEL Source for comparison

Encircled Flux: Field Qualification? Issue is to guarantee the EF compliance at the end of launch cord

Solution 1: Use Modally transparent cords to remove Modal distortion due to the ref. cords

Solution 2: Use matched cords with light sources to guarantee compliance Solution 3: Use external mode conditioner with a non-EF light source

Laboratory grade equipment available commercially to verify EF launch Eg: Arden Photonics Modal Explorer, Photon Kinetics Launch Analyzer

Encircled Flux: Benefits Reduction of uncertainty in Fiber loss measurements

Between different manufacturers

Improved repeatability of measurements

Apart from standards compliance, very meaningful in 10GbE and going forward in 40GbE installations due to their tight insertion loss requirement

IL using EF launch, how different? Test Setup (Tested with both non EF, EF Adapters)

Tx Rx Tx Rx

Δconn1 Δconn4Loss Measured = Δconn1 + Δconn2+ Δconn3 Δconn4

Δconn3Δconn2

2m Link

Tx Rx Tx Rx

Δconn1 Δconn4Loss Measured = Δconn1 + Δconn2+ Δconn3 Δconn4

Δconn3Δconn2

20 m Link

Test Methodology Measured a 2m link and a 20m link Tested with both non EF and EF compliant adapters Every measurement was taken immediately after reference Tested with both 1-Jumper and 3-Jumper reference EF light source qualified with Arden Photonics, Modal Explorer

IL using EF launch, how different? Results

Difference between EF and non EF (average of 28 measurements on same link at 850 nm) 1 Jumper Reference : 1.14 dB (link loss 6 dB, 19% less

with non EF) 3 Jumper Reference : 0.7 dB

Standard Deviation of measurements between non EF and EF

EF Launch (28 samples) 1 Jumper method : 0.14 dB 3 Jumper method : 0.16 dB

Non EF Launch: (28 samples) 1 Jumper method : 0.209 dB 3 Jumper method : 0.215 dB

Conclusion and Findings: The EF launch measures higher loss of the link, possibly closer to the real loss with a

difference of 1.14 dB 1 Jumper method results in an uncertainty slightly lower than 3 jumper

Encircled Flux Standard in Multimode testing The new IEC Standard

14763-3

Referencing: One Jumper

Fiber1 Loss measured by instrument is Reference Value subtracted = Lconn1 + Lconn4 Optical loss limit should be calculated as follows, Lconn1 + Length of Fiber * Loss/km (dB) + Lconn2 + Lsplice1 + Lsplice2 + Lconn3 + Lconn4 What is special about Lconn2 and Lconn3 ?

Optical Budget: Refresher (MMF)

Fiber1 Loss measured by instrument is Lconn1 + Lconn2 + Lsplice1 + Lsplice2+ Lconn3+ Lconn4 + Lfiber But what we need to certify is: Lconn1 + Length of Fiber * Loss/km (dB) + Lconn2 + Lsplice1 + Lsplice2 + Lconn3 + Lconn4

Typical Deployment Patch Panel Patch Panel

Permanent Link

Reference grade Launch cord

Reference grade Tail cord

Referencing: One Jumper contd…

Reference Connector to Reference Connector mated loss : 0.1 dB Reference Connector to Random Connector : 0.3 dB Random to Random Connector :0.75 dB Limit14763-3= Length of Fiber * Loss/km + 0.3 + Lsplice1 + Lsplice2 + 0.3 dB = 0.6 dB + Length of Fiber * Loss/km (dB) + Lsplice1 + Lsplice2 LimitTIA/11801= Length of Fiber * Loss/km + 0.75 + Lsplice1 + Lsplice2 + 0.75 dB

Ref plug mated to random jack

Referencing: Three Jumper

Reference Connector to Reference Connector mated loss : 0.1 dB Reference Connector to Random Connector : 0.3 dB Limit14763-3 = Fiber * Loss/km + (0.3 – 0.1) + Lsplice1 + Lsplice2 + (0.3 – 0.1) dB = 0.4 dB + Length of Fiber * Loss/km (dB) + Lsplice1 + Lsplice2 LimitTIA/11801= Length of Fiber * Loss/km + 0.0 + Lsplice1 + Lsplice2 + 0.0 dB

Ref-ref mated

Encircled Flux Standard in Multimode testing MPO/MTP Testing

Testing issues in 40GbE Fiber

Polarity Issues Multiple types of MPO cords in the market,

causing a lot of confusion Need for a graphical framework to provide

“wiremap” like features •

TYPE A TYPE B TYPE C

MPO Testing: Breakout and Cassettes

Interoperability between 10G->40G links Most installations use break-out cables to get 10G links Test Instrument should be able to support LC on one end and MPO on the remote unit

MPO/MTPLIGHT SOURCE

LC Adapter

Testing for Insertion Loss: Methodology

Broadly two different solutions are available Testing using test adapters with MPO/MTP connectors

Pros Quick way to test all 12 fibers in a matter of seconds Ability to test breakout links, cassettes Ability to test polarity of the fiber and continuity quickly Less prone to errors

Cons No reference grade MPO launch cord specified in standard No loss limits defined in the cabling standards yet

Testing with a LC Adapter + MPO fan-out or a breakout reference cable

Pros Can guarantee a EF launch at the end of launch cord Cheaper way to test MPO trunks by re-using LC adapters

Cons Too many to mention here

Testing for Insertion Loss: Methodology

Current state of Standards Standards don’t yet define a reference grade MPO launch cable

Loss of ref-ref mated connector, ref-random not defined yet

3 Jumper reference recommended assuming a channel test for MPO trunks

Pass/Fail Criteria for MPO trunks

Can use IEEE limits to test for 40GbE specification 1.5 dB for OM4 and 1.9 dB of OM3

Use premise cabling standards like ISO/IEC 14763-3, TIA 568 C.3 etc.

MPO Testing with the IEEE Limit (sample workflow)

Select 40G/100G limit Based on the fiber type, OM3/OM4 and the application selected, the loss limit is applied.

The channels are appropriately selected when the test limit is selected.

Testing with premise limits and MTP light source/ Power Meter - Referencing

Using the 3-Jumper test reference scheme

Launch cord (Type A) Tail Cord (Type A)

Ref Cord (A/B/C) Should be same as trunk type

MPO/MTP Light Source

MPO/MTP Power Meter

Testing with premise limits and MTP light source/ Power Meter - Testing

Tests absolute power, loss and polarity

Launch cord (Type A) Tail Cord (Type A) Remove ref and connect Trunk under Test

MPO/MTP Light Source

MPO/MTP Power Meter

Either (A/B/C)

Testing with premise limits and MTP light source/ Power Meter - Referencing

Using the 1-Jumper test reference scheme with Gender/type interchangeable cords

MPO/MTP Light Source

MPO/MTP Power Meter

Unpinned- Unpinned cord(A)

Testing with gender/type interchangeable cords.

Launch cord (Type A) New Tail Cord (Type A) Trunk under test

MPO/MTP Light Source

MPO/MTP Power Meter

Gender changed to male (pinned) on one side

Uncertainty between 1 and 3 Jumper reference

Setup Tested a 6x20m trunks 4 times with both one jumper and three jumper reference

Results Std Deviation with 1 Jumper Reference : 0.08 dB Std Deviation with 3 Jumper Reference : 0.19 dB Average difference between 1 and 3 jumper reference : 0.28 dB

Conclusion and learnings

IEEE limits by far accepted by many large datacenters (eg: Facebook) Can re-use 14763-3 limit for MTP testing barring compliance to EF

launch condition Uncertainty with the MTP/MPO adapters quite low and provides a

much better method to qualify trunks (see next slide) Most of the issues for trunk cables observed are no-connect, incorrect

polarity or unclean connectors. Using MPO/MTP adapters to qualify the links still the most practical

way to enforce qualification in the field

Thanks for listening.

Happy testing!

Elie@psiberdata.com