best practices for testing parallel optics · tier 2 testing of mpo • tier 1 testing cannot...

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

3© 2018 Viavi Solutions Inc.www.viavisolutions.com 3© 2017 Viavi Solutions Inc.www.viavisolutions.com

Basics


Is MPO New?

No – MPO connectors and ribbon fiber have been around for well over a decade


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


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


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


1G/10G Networks


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


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


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


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


Polarity

Key Up/ Key Down

Key Up/ Key Up


Adapter Polarity


Focused on the Connection

Adapter

MPO Unpinned

(Female)

MPO Pinned

(Male)

Courtesy of US Conec


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.


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


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

19© 2018 Viavi Solutions Inc.www.viavisolutions.com 19© 2017 Viavi Solutions Inc.www.viavisolutions.com

Test and

Certification


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


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


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


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


Inspect Before You Connectsm

Follow this simple “INSPECT BEFORE YOU CONNECT” process to ensure fiber end faces are clean prior

to mating connectors.


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


Inspect ALL fibers in a Multi-Fiber Connector


IEC 61300-3-35 Sets Requirements for Connector Quality

Multimode MPO Connectors

CLADDING Zone

CORE Zone

Even for MPO!


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


Real End-Face Examples

Cracked MPO Happy MPO


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


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


MPO to MPO Tier 1 Certification

• Test MPO Links and Channels

• Loss, length and polarity

MPO BackboneMPO BulkheadMPO Bulkhead

MPO Test Cords


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


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


Schematic test results (pass example)


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


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


Q&A

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Thank Youwww.viavisolutions.com/MPO

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