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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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Inte
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Pixels along x-axis Pixels along y-axis Position of pixels
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nsity
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©Psiber Data
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