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Best Practices for
Testing Parallel Optics
5th June 2018
Product Manager
Tom Ronan
2© 2018 Viavi Solutions Inc.www.viavisolutions.com
Agenda
• Basics
- Why parallel optics with multi-fiber push-on/pull-off (MPO) connectors?
- System architectures
- Standards
- Technology overview
• Test and Certification
- End-face inspection and certification
- Polarity check
- Tier 1 (basic) certification
- Tier 2 (enhanced) certification
- Troubleshooting
• Wrap up
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Basics
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Is MPO New?
No – MPO connectors and ribbon fiber have been around for well over a decade
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Why MPO?
• Relentless need for speed
• MPO being extended to equipment
• Switches and servers
• QSFP ports
• Port density and fiber
consolidation
• Still breaking down to LC
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Density & Speed of Deployment
Fiber density is a
problem With MPO, 6x or 12x the fiber in
the same footprint as LCMPO lets you deploy many
fiber ports quickly
144 fibers
24 fibers
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Interface Reach Medium Parallelism Standard
100GBASE-ER4 40 km SMF 4 λ / dir IEEE 802.3ba
ER4-Lite 20-25km SMF 4 λ / dir Variation on 802.3ba
100GBASE-LR4 10 km SMF 4 λ / dir IEEE 802.3ba
CWDM4 2 km SMF 4 λ / dir CWDM4 MSA
CLR4 2 km SMF 4 λ / dir CLR4 Alliance
PSM4 500 m SMF 4 fibres / dir PSM4 MSA
SWDM4 100 m OM5 MMF 4 λ / dir SWDM Alliance
100GBASE-SR4 70 m
100 m
OM3 MMF
OM4 MMF
4 fibres / dir IEEE 802.3bj
100GBASE-SR10 100 m
125 m
OM3 MMF
OM4 MMF
10 fibres / dir 802.3ba
SWDM4/SR4 100mPSM4 500m
CWDM4 / CLR4 2km
Newer Data Center Interfaces:
100GE Client Interfaces – 2018 View
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1G/10G Networks
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Migrating to 40G/100G Network
Cassettes are replaced by MPO adapter panel
Patch Cord is now 12-fiber with MPOBackbone now supports one
40/100GbE channel, using 8 fibers
instead of six duplex 10GbE channels
40/100G BASE-SR4 Lane Assignments
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Anatomy of a 12-fiber Multi-Mode MPO Connector
Note: MPO connectors with higher fiber counts (e.g. 24) will have multiple rows of fiber on the ferrule
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MPO Connectors are more likely to be contaminated
1.25mm ferrule = 1.2mm2 area 9.5mm X 5.0mm opening = 47.5mm2 area
If 1 fiber is 95% likely to be clean,
12 fibers are (0.95)12 = 55% likely to be clean
Single-Fiber Connector MPO Connector
White ceramic ferrule
One fiber per connector
Common types include
LC, SC, FC, and ST
Smaller Surface Area
Polymer ferrule
Multiple fibers in linear array
6x or 12x density connectivity
Larger Surface Area
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Far more area and probability of contamination
1.25mm sleeve = 1.2mm2 area 9.5mm X 5.0mm opening = 47.5mm2 area
Probabilities scale exponentially:
If 1 fiber is 95% likely to be clean,
12 fibers are (0.95)12 = 55% likely to be clean
MPO adapters have no
sleeve or alignment feature,
they are wide open
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Polarity
Key Up/ Key Down
Key Up/ Key Up
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Adapter Polarity
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Focused on the Connection
Adapter
MPO Unpinned
(Female)
MPO Pinned
(Male)
Courtesy of US Conec
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Focused on the Connection
Physical Contact The Physical Contact area is the critical
joining point in the fiber network. If there is
no clean physical connection, the light
path is disrupted and the connection is
compromised.
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Top-view Cross Section 12 Fiber MPO - Clean
Physical Contact
Example of
Clean Connection(no contamination)
1
2
3
4
5
6
7
8
9
10
11
12
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Top-view Cross Section (1–12 Fibers)
Particle Dirt
Example of
Dirty Connection(contamination causing air gaps, back
reflection, insertion loss)
Air Gap1
2
3
4
5
6
7
8
9
10
11
12
Dirt
Back Reflection
Insertion Loss
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Test and
Certification
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IEC Standards Related to Fiber Testing
Information technology -
Implementation and operation of
customer premises cabling - Part 3:
Testing of optical fibre cabling
Information technology -
Generic cabling for
customer premises
SC 25 WG 3
SC 86C WG 1
Test Procedures
General
communication
subsystems - Light
source encircled flux
measurement method
Installed cable plant -
Multimode attenuation
measurement
Installed cable plant -
Single-mode attenuation
and optical return loss
measurement
Visual inspection of
fibre optic
connectors and fibre-
stub transceivers
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TIA Standards Related to Fiber Testing
• 568.3-D – Optical fiber cabling and component standard
- Updated to revision “D” in October 2016
- Transmission performance and test requirements in Clause 7
- Annex E (informative) provided guidelines for field testing
• ANSI/TIA-526-14-C-2015
- Test procedures for installed multimode fiber cable plant
- Released in April 2015
- Adaptation of IEC 61280-4-1 Ed. 2.0
- Encircled Flux for 850nm/50 micron
• ANSI/TIA-526-7-A
- Test procedure for installed single mode fiber cable plant
- Released in July 2015
- Adoption of IEC 61280-4-2 Ed 2.0
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Simplex/Duplex vs. MPO Testing
• Existing fiber test standards do not address MPO-specific concerns
• SC 86C WG 1 released a Technical Report (TR) on testing MPO
Testing Multi-fiber optic
cable plant terminated with
MPO connectors
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Tests Defined in Standards
• Both TIA and ISO/IEC standards specify two tiers of certification
- Tier 1 (or basic): loss, length and polarity
- Tier 2 (or extended): Optical Time Domain Reflectometer (OTDR)
• Tier 2 (extended) tests are an optional addition to tier 1 (basic) tests
• Fiber end-face inspection and certification is also a requirement to ensure pristine
end-face condition PRIOR to mating
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Inspect Before You Connectsm
Follow this simple “INSPECT BEFORE YOU CONNECT” process to ensure fiber end faces are clean prior
to mating connectors.
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Inspect and Clean Both Connectors in Pairs
Inspecting BOTH sides of the connection is the ONLY WAY to ensure that it will be free of
contamination and defects.
Patch cords are easy to access and view compared to the fiber inside the bulkhead, which is frequently overlooked. The
bulkhead side may only be half of the connection, but it is far more likely to be dirty and problematic.
Patch Cord (“Male”) Inspection Bulkhead (“Female”) Inspection
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Inspect ALL fibers in a Multi-Fiber Connector
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IEC 61300-3-35 Sets Requirements for Connector Quality
Multimode MPO Connectors
CLADDING Zone
CORE Zone
Even for MPO!
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CLICKER FOR CLEANING MT END FACES
Clickers are good for cleaning end faces during
network installations
Cleans both in adapter/cassette and patch cords
Uses micro woven ultrasonically cut cleaning
ribbon
Best Practice for Wet-Dry:
Apply small amount of cleaning fluid to an optical
grade wipe
Touch the cleaning tip of the clicker on the wet
spot on the wipe
Do NOT apply the cleaning fluid directly to the
cleaning ribbon
Cleaning MPO Connectors
Courtesy of Sticklers
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Real End-Face Examples
Cracked MPO Happy MPO
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Polarity Check (AKA Fiber Map)
• For existing installations, the end-to-end
polarity is often not known
• Polarity Check tool shows the polarity of
the system
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Main Challenge for Tier 1 Testing of MPO
• One-cord reference
- If test set has pinned ports then unpinned to unpinned test cord must be used
to perform reference
- Receive cord is then added (unpinned to unpinned)
- Can then test a pinned system, but cannot verify reference without adding a
third cord
• There are MPO connectors available that allow pins to be retracted or removed
- Helps solve pinned/unpinned challenges
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MPO to MPO Tier 1 Certification
• Test MPO Links and Channels
• Loss, length and polarity
MPO BackboneMPO BulkheadMPO Bulkhead
MPO Test Cords
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Selecting Channels
• Can apply to any of the above scenarios
• Allows selection of which of the 12 channels are
part of pass/fail analysis
• Eliminates false fails in cases when 8 or fewer fibers
are present in MPO links (e.g. 40GBASE-SR4)
• Results reflect topology
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Tier 2 Testing of MPO
• Tier 1 testing cannot ensure individual event (splices and connection) losses are
within spec OR the cable attenuation is uniform
• Tier 2 (OTDR) testing adds the characterization of these events to the certification
test
• Tier 2 testing is also the ideal fiber trouble shooting tool to find the cause AND
location of excess loss (incl. breaks) and reflectance
• Requires MPO switch (ideally)
• Pinned/unpinned systems require different launch and receive cords
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Schematic test results (pass example)
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Identify front and back connectors in cassettes• Conventional OTDRs can’t distinguish between front and back connectors of a cassette
• If ribbon connector (back) is damaged/dirty, maintenance of the connector/replacement can affect
multiple fibers/services (up to 10 channels)
• If front connector (single) is damaged/dirty, maintenance of the connector/ replacement will affect only
one fiber/ channel.
• Enhanced DZ OTDR
• Identifies quickly front and back connectors’ cassettes avoiding unnecessary service/traffic disruption
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Wrap-up
• MPO end-face condition is the most critical element in a channel with MPO connections
• Polarity can be a challenge – especially when adapting existing MPO backbones to new services
• Be aware of pinned/unpinned – presents challenges for testing (test cords must mate with system – challenges with test device and test cord gender)
• Tier 1 (loss/length/polarity) testing is typically done on links
- 1/10G MM, 1/10/40/100G SM link is duplex
- 40/100G MM, PSM4 SM link is MPO
• OTDR testing of MPO allows for:
- Characterization of the link or channel (uniformity of cable attenuation and connection loss)
- Fault isolation to prevent unnecessary service interruptions
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Q&A
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