New Requirements in Acceptance Testing for Fiber Installations · IEEE 802.3ba: 40/100G Ethernet Approved (June 2010) 10G 40G 100G Approach Laser Type Fiber Type Connector Transceiver

New Requirements in Acceptance Testing for Fiber InstallationsRodney Casteel RCDD/NTS/OSP/DCDC, CommScope, Chair TIA FOTC

Adrian Young, Fluke, FOTC Standards Co‐ChairRobert Reid, Panduit

Ed Gastle, JDSULee Kellett, AFL

Agenda• Who Is FOTC – Rodney Casteel• Standards Update – Ed Gastle• High Speed Fiber Plant for Data Centers:

– High Speed Channels and Drivers – Rodney Casteel– Cabling & Application Standards – Robert Reid

• Fiber Cleaning & Inspection – Lee Kellett• Fiber Testing & Troubleshooting

– Adrian Young– Ed Gastle

• Final Questions

Fiber Optics Technology ConsortiumOverview:

• Part of the Telecommunications Industry Association (www.tiaonline.org)

• Until 2013, we had been known as the Fiber Optics LAN Section (FOLS). Our new name was chosen to reflect our expanding charter.

• Formed 21 years ago• Mission: to educate users about the benefits of deploying fiber in

customer‐owned networks• FOTC provides vendor‐neutral information

Fiber Optics Technology Consortium

www.tiafotc.org TIA Fiber Optics Technology Consortium

Current Members

• 3M• AFL• Corning• CommScope• EXFO• Fluke Networks• General Cable

• JDSU• OFS• Panduit• Sumitomo Electric Lightwave• Superior Essex• TE Connectivity

Fiber Optics Technology Consortium• Maintain a website with Fiber FAQs, White Papers and other

resources – www.tiafotc.org.• Developed and maintain a free Cost Model that allows users to

compare installed first costs of several architectures.• Host a webinar series throughout the year with all webinars

available on demand.• Speak at industry conferences like BICSI• Contribute to industry publications – check out our article on

Making Networks Greener in BICSI News.• Conducting market research

Fiber Optics Technology Consortium• Recent Webinars Available on Demand

– Design & Deployment Best Practices for Reliable Industrial fiber Optic Networks

– Beyond Bandwidth: Managing Your Assets in Today's Fiber Network– Getting it Right the First Time: Reducing the Time & Cost of Retesting

• Visit www.tiafotc.org or our channel on BrightTalk

Webinars are eligible for CEC credit for up to two years after they are first broadcast. Email [email protected] if you have completed a webinar and want to receive your CEC.

www.tiafotc.org TIA Fiber Optics Technology Consortium

Standards Update

Ed GastleJDSU

Standards Update (TIA)

• 568.3 – Optical fiber cabling and component standard• Being updated to revision “D” – along with 568.0 and 568.1

– Ballot 3 reviewed at TR42 meetings on Feb 2‐6, 2015• Transmission performance and test requirements will be in Clause 7• Annex D will provide guidelines for field testing

Higher Speed Channels

Rodney Casteel RCDD/NTS/OSP/DCDC CommScope

Market Drivers

• 60% increase in Global Internet users by 2018.

• 75% increase in Global networked devices by 2018.– (Approximately 3 devices and/or connections per person on the planet)

• Fixed broadband speeds will increase 2.6x Globally by 2018.

• IP video will represent 79% of all traffic by 2018.

Cisco Visual Networking Index (VNI):Forecast and Methodology, 2013-2018June 2014

Global Mobile Data Traffic Growth

“Cisco VNI: Forecast and Methodology,

2013-2018"February 2014

18

16

14

12

10

8

6

4

2

01.5 EB

2.6 EB

4.4 EB

7.0 EB

10.8 EB

15.9 EB

2013 2014 2015 2016 2017 2018

EB = Exabyte1,000,000,000,000,000,000

Market Drivers

• Global data center IP traffic by 2017 will reach 7.7 zetabytes or 644 exabytes per month.

• Global Cloud IP traffic will reach 5.3 zettabytes in 2017 which is a 4.5x increase

• Global Cloud IP traffic will account for two‐thirds of total data center traffic by 2017.

Cisco Global Cloud Index: Forecast and Methodology, 2012 - 2017

By 2020 the average person will maintain 130 terabytes of personal data.

Storage Requirements

Source: IDC

40

35

30

25

20

15

10

5

02012 2020

1 ZB = 1 billion TB1,000,000,000,000,000,000,000

Zeta

byte

s (Z

B)

Global storage capacity forecast through 2020

2.59

7.23

2017

40.00

Source: Cisco IBSG

Cabling Infrastructure impacts the success of implementation

Cloud Virtualized Green

Big Data ConvergedDCIMSDN

EthernetInfinibandFCoE

iSCSi Fibre Channel

Data center emerging trends

Density ScalabilityBandwidth Manageability

Changing infrastructure requirements for the data center

L3

L2

The cloud and physical infrastructure

• High bandwidth, low latency required to support L2 switch links

• Scalable infrastructure essential

Traditional Data Center Cabling Infrastructure

Core Layer

Aggregation Layer

Access Layer

Reference Architecture

Server Row Equipment Distribution Area

Core Switch Main Distribution Area

Core Switch

Fiber/CopperPatching

(includes FC network)

ConsoleServer

Fiber PatchingAggregation

Switch Access Switch

Laser Optimized MM Structured CablingCategory Copper CablingSFP+ Twin-Ax Copper

Newer Data Center Architecture• Spine‐Leaf offers a lower

latency option for server to server communications

• Offers more redundancy• Requires higher density

connections between leaf and spine switches

• Any to any concept

• Typical pre-term copper install is eighttimes faster than field term

• Reduces deployment risk

• “Migration” to 40/100GbE on fiber is much less disruptive

• Minimal packaging and waste on site -GREEN

Installation time dramatically reduced

Pre‐terminated cabling: Scalable and Quick

IEEE 802.3ba: 40/100G EthernetApproved (June 2010)

10G 40G 100GApproach

Laser Type

Fiber Type

Connector

Transceiver Tolerances

MaximumDistance

* 150 meters with OM4 requires low loss connectorsExtended reach out to 300m on OM3 and 400m on OM4 possible with alternate transceivers

# of Fibers

10G x4

VCSEL Array

OM3/OM4

MPO

Relaxed(to lower cost)

OM3: 100+ m*OM4: 125 – 150 m*

12

10G x10

VCSEL Array

OM3/OM4

MPO x 2

Relaxed(to lower cost)OM3: 100+ m*

OM4: 125 – 150 m*

24

10G

VCSEL

OM3/OM4

LC x2

Tight

OM3: 300mOM4: 550m

2

40GBASE‐eSR4 QSFP+Emerging Defacto Standard

• “Extended Reach” transceivers now available– Cisco / Dell

• Operates as 4 x 10G– QSFP+ has 2.5X edge‐density for 10GBASE‐S

• Operates as 1 x 40G– 300m (OM3) or 400m (OM4) vs. 100/150 for Std –SR4 device

• Lower cost alternative to SM (40GBASE‐LR4 QSFP+)– Lower CAPEX – Estimated 75%– Lower OPEX – 50% of power dissipation (1.5W vs. 3.5W)

• 2 Wavelengths at 20G line rate– 850nm & 900nm– < 3.5W Power Dissipation– Utilizes duplex LC connectivity– Compatible with Nexus 9000 series

• Low Loss connections (with 4LC & 4MPO connections)– OM3 – 100m– OM4 – 125m

Cisco QSFP40G BiDi

Serial Duplex Cable PlantTransmission Example ‐ 10GBASE‐SR

Structured Cabling ‐ 10G Ethernet Cross Connect Model with MPO Cassettes

“Parallel Optics” Cable Plant ‐ Parallel Transmission Example ‐ 40GBASE‐SR4

Structured Cabling ‐ 40G Ethernet Cross Connect Model with MPO Cassettes

“Parallel Optics” Cable PlantMulti‐Row Parallel ‐ 100GBASE‐SR10

PUSH

PULL

PUSH

PULL

Position 1

Position 12

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Key-up to key-upmated connections


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Type-B:1-1array cables

Type-B:1-1 array patch cords

Example optical channel

B

B

B

B

PUSH

PULL

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Position 1

Position 12

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:

RxRx

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:

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TxTx

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Type-B:1-1array patch cords

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Example optical channel

B

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Transceiver

:

RxRx

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:

:

TxTx

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:

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:

:

TxTx

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:


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Example optical channelExample optical channel

BB

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:

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“Parallel Optics” Cable PlantMulti‐Row Parallel ‐ 100GBASE‐SR10

Higher Speed IEEE RoadmapOngoing 802.3 Efforts

Parallel Optics• 100GBASE‐SR4

– 0 to 106m: 100G over OM4, Parallel multimode fiber (850nm)

– 4x25G QSFP+ with MPO

• 100GBASE‐UR4– 0 to 20m: 100G Ultra‐short reach,

Un‐retimed parallel optics – 4x25G QSFP+ with MPO

• 100GBASE‐PSM4– 0 to 500m: 100G Over single‐mode

fiber (1310nm window)

Single‐mode Duplex• 40GBASE‐ER4

– 0 to 40000m: 40G Ultra‐long reach over single‐mode fiber

– In support of Metro Area Networks– Extended reach option to 40GBASE‐LR4– Same CWDM wavelengths, 20km and

40km options

Cabling & Application StandardsAssuring Application Compliance

Robert Reid Panduit

Ethernet Loss Budgets“Where did my power budget go?”

System Designer Uncontrolled Power Penalties

• Deterministic Jitter Noise

• Reflection Noise

• Relative Intensity Noise (RIN)

• Mode Partition Noise (MPN)

• Modal Noise (MN) = 0.3dB (function of CIL)

• Margin (Headroom) = 0.8dB

10 Gb/s MM Cabling SystemIEEE Link Model 850nm Serial, 300m, 2000MHz.km MMF

System Designer Controlled Power Penalties

• Channel Insertion Loss (CIL) = 2.6dB

= 1.5dB (connectors) + 1.1dB (fiber)

• Inter-symbol interference (ISI) = 3.02dB

• Both can be controlled and changed

• 75% of the Budget

Power Budget(7.3dB)

A

C

B

ISI

CIL

ISI

CIL

Margin

8

7

6

5

4

3

2

1

0

10 Gb/s MM Channel ModelISI Power Penalty vs Link Length (km) ‐ Different Fiber Grades

10GbE model allows ISI Power Penalty of 3.018dB @ 300m ISI scales with DMD - lower DMD means lower power penalties

10 Gb/s MM Channel ModelCabling Vendor Models ‐ “Engineered Channels”

Application standards can be ambiguous ‐ Industry perception of a hard budget limit of 2.6dB for 10GBASE‐SR channel for example

Response ‐Many requests for design help from customers (10G links are new to some). Typically vendors have Excel‐based calculators or tabulations of reach and power budget for different fiber types (bandwidth), connector styles and total insertion loss.

Implications: • ‘Overspecification’ of fiber media without tools/tables• Design choices ‐ 2.6dB for SR limit narrows component selection and can limit

flexibility choices for cable plant (cross‐connect)• Erroneous/unrealistic test limit specification

10 Gb/s MM Channel ModelCabling Vendor Models ‐ “Engineered Channels”

10 Gb/s MM Channel ModelCustomer Example ‐ Value Proposition for OM4

317 meter design goal ‐ Beyond 300 SR channel

System ‘A’ ‐ OM3 Fiber throughout with standard pigtails (0.3dB)System ‘B’ – OM3 Fiber throughout with ‘optimized’ pigtails (0.2dB)System ‘C’ – OM4 Fiber throughout with standard pigtails (0.3dB)System ‘D’ – OM4 Fiber throughout with ‘optimized’ pigtails (0.2dB)

OM4 value:0.7dB additional headroom at target reach, or additional reach beyond the target

10 Gb/s MM Channel ModelCustomer Example ‐ Value Proposition for OM4

Channel Insertion Loss (CIL) = 1.9dB

= 1.5dB (connectors) + 0.4dB (fiber)

Power Budget(8.3dB)

100 meter Channel

Source: IEEE

40/100G Fiber Cabling40GBASE‐SR4/100GBASE‐SR10 Channel Budget

• Trade‐off between SCS ‘wants’ and IEEE requirements

100 meter OM3 channel with two 0.75dB (Max.) connectors (1.5dB connector insertion loss total)

150 meter OM4 channel with two 0.50dB (Max.) connectors (1.0dB connector insertion loss total)

“Engineered Link”

40/100G Fiber CablingLink Power Budgeting for Cabling

0.100.200.300.400.500.600.700.800.901.001.101.201.301.401.501.60

100 110 120 130 140 150 160 170 180 190 200

Total Con

nector Loss (dB

)

Maximum Reach (m)

OM3OM4

Source: Panduit extrapolation from IEEE model

‘Flexible’ Application Loss Budgets10G MM Cross‐Connect Cable Plants

‘Flexible’ Application Loss Budgets40/100G MM Cross‐Connect Cable Plant

‘Flexible’ Application Loss Budgets“10G/40G” Cable Plant Reach (Ethernet)

Connector Loss Max = 0.75dB;Splice Loss max = 0.30dB

Fiber Attenuation Max = 3.5dB/km

IEC Definition of Loss BudgetISO/IEC 11801 ‐ Backbone/Horizontal Links

Gage R&R (Gage Repeatability and Reproducibility) Measurement variation introduced by the LSPM system, which consists of the LSPM itself and the individuals using the instrument(s).

1. Repeatability ‐ variation from the LSPM(s)2. Reproducibility ‐ variation from the individuals using the LSPM(s)3. Overall Gage R&R, which is the combined effect of (1) and (2)

Expressed as a percentage of the loss budget limits, and a value of 20‐30% Gage R&R or less is considered acceptable in most cases.

Example: 1.85dB loss budget (2, 0.75dB connectors & 100m of 3.5dB/km MM fiber)

Acceptable R&R value would be 30 % of 1.85dB (0.6dB) (error of measurement std. dev. of about 0.1dB is then required)

Link CertificationThe Importance of Link Measurement CAPABILITY

A Gage R&R study quantifies the inherent LSPM variation, but bias (accuracy) must be verified through a external calibration process.

Link CertificationCAPABILITY (Precision) vs BIAS (Accuracy)

Types of Measurement ErrorsRepeatability and Reproducibility of Gauge

RED = “Ideal Gauge”GREEN = Actual GaugeBLUE = Link Loss Distribution

About 10% chance of failing a good link @ about 1.5dB (but there are practically no links here)

About 10% chance of passing a failing link @ about 2.1dB (and some links are here)

Gauge R&R

False Positive False Negative

Pro

babi

lity

of L

ink

Acc

epta

nce

Test

Lim

it

Test

Lim

it

False positive…link indicates fail but truly a pass• Impacts the customer’s ability to deploy links in a timely fashion ‐ “Profitability Issue”

False negative…link indicates pass but truly a fail• Presents link reliability issues and potential warranty claims ‐ “Day two issue”

Both errors minimized by providing excellent LSPM capability against stated application loss budget (getting tighter based on application and more connectors in the channel).

Link Loss RecommendationsContractor Test Error Types

Link Certification“One Jumper”Method

Several link test configurations exist as defined by standards. The goal of testing any link should be that the impact of the tester referencing cables minimized so that the result of the test is not biased.There are three standard methods of completing a link loss test:

• One Jumper Method • Two Jumper Method • Three or “Golden” Jumper Method

Last two methods have measurement ‘artifacts’ that cannot be effectively subtracted out & overall yield higher link measurement uncertainty & BIAS

• MM test links were built with various lengths and numbers of connectors• Several personnel were used to measure perm links• Reference cords were used for all methods

• 5.15 sigma’s (99%) of measurement error for last two > 1.0dB• These methods are NOT recommended in links with tight

application budgets (variability is a significant fraction of the link budget specification)

Link Loss Method Comparison

‘Commissioning’ Testing(Contractor #1)

‘Witness’ or Audit Testing(Customer)

New Testing(With Reference Cords)

Re-reference Events -taken from lag in time stamps of Tester data (not all events shown)

Link CertificationCustomer Example #1 ‐ Non‐use of Reference cords (Time Based Variability)

• Significant Diff. in average Headroom between Audit and Commissioning link tests

• Extremely poor reproducibility

• Consumes Headroom spec

Link CertificationCustomer Example #1 ‐ Reproducibility of Measurements

Expectation - Strong relationship between audit tests and commissioning tests and the ability to predict one from the other

Result - Poor relationship between tests (random) and no ability to effectively predict one from the other

Link CertificationCustomer Example #1 ‐ Correlation of Measurements

Link CertificationCustomer Example #1 ‐ Contamination (Time/Location Based Variability)

Contingency Analysis of ‘Status’ By ‘Rack Unit ID’(Failure rate as a function of test location)

Large DC account indicated that they were encountering such a high failure rate of link failures for pre-terminated, cassette-based 10G multimode plug and play fiber product at their data center, that testing was halted until root case was found and rectified (50-60% failure rate of links before testing was stopped).


Distribution Analysis of Headroom by Date Tested(Failure rate as a function of test time)

Out of Control In Control


• Unlikely that products could have been supplied that would produce a linearly increasing failure rate (conclusion is that this is not ‘nature’or related to natural variation of the product)

• Systemic testing issues at play (damaged reference cords or the like)• Discrepant links retested with the best practices in inspection, cleaning

and proper use (and care) of reference patch cords• All of links that were that previously failed, passed with significant

headroom to the standard when retested• Customer has since adopted cleaning/inspection practices on reference

cords and links under test, and this has had significant impact on their measurement capability and stability of measurements in particular

Best PracticesConnector Inspection and Cleaning

Lee Kellett, AFL

Why Do We Care?

• Connector contamination and damage is the leading root cause of fiber optic network failures.

• Network failures cause downtime and truck rolls.• Lower loss budget requirements make cleaning even more important than before.

• Inspecting and cleaning before connecting saves troubleshooting costs, downtime and improves performance. Period!

How Dirty Can It Be?

Let’s Do The Math...

What Happens?

• Dust and dirt can literally block the light • Dirt and oils can cause light to refract and be lost at the connection

• Particles can prevent proper mating of connectors • Dirt can damage connector end face when mating and cause permanent damage – cleaning will no longer help

Clean connectors matter!

Dirty connectors = high insertion loss and high reflectance Clean connectors = low insertion loss and low reflectance

Take a newly cleaned and installed connector...

Now add a test lead – not cleaned

And voila... Cross‐contamination

Why Inspect, Clean, Inspect?

• Inspect first to determine need for cleaning• Dry cleaning is quite effective, but is not perfect – so inspect after clean

• Many customers now require proof of inspection to certify installations

• Inspecting first verifies pre‐connectorized products have been supplied in good condition

• Saves time and money in the long run

What Equipment Do I Need?

• A good inspection scope – Auto pass/fail analysis is best; Manual/view only is better than nothing

– stand alone or connected to your other test equipment

• Cleaning supplies– Dry is ok but having a wet solution available is preferred – Make sure they are designed for fiber – tissues don’t work!

Reality CheckWHAT WE HEAR...• I have not had issues – a quick

rub on my shirt works

• I cleaned – no need to inspect or I just unpacked new jumpers

• It takes too much time – not worth it

REALITY...• YIKES! High speed networks of

today are not forgiving

• If there are issues – how will you prove it was not you? How do you know cleaning worked?

• How much does it cost to replace connectors? Or deploy someone to troubleshoot later?

It’s Not Just Us!

• There are IEC standards that define pass/fail criteria• Cisco has a 20+ page document detailing cleaning and inspection procedures for fiber connectors

• AT&T has their own pass/fail criteria and a 112 page document on inspecting and cleaning

• All of us on this panel, and many more at this conference agree ‐ this is a fundamental requirement for today’s networks.

Best Practices ‐ Summary

• Inspect, Clean and Inspect every connector– Assures optimum performance– Prevents damage– Saves time and money in the big picture – less downtime, fewer truck rolls, less damage and replacement

– Assures performance needs will be met– Provides a better product to your customers

TIER 1 CERTIFICATION

Ed Gastle, JDSU

What is Tier 1 Fiber Certification?

• Tier 1 Fiber Certification:• Measure Length• Measure Loss• Check Polarity

• Ensure Loss does not exceed a “limit”(AKA loss budget)

• Document results

A Consistency Challenge

Tech ATester A

Tech ATester B

Tech BTester B

Tech BTester A

If different results –different best practices

If different results –different tester specifications

Leading Causes of Inconsistent Results1. Fiber end-face condition

– Covered already2. Reference method selected matches

physical configuration and was properly performed

3. Multimode Transmitter Launch Condition – The dreaded Encircled Flux!

…is there are so many to choose from!

A Brief Note on StandardsThe wonderful thing about standards…

Relevant TIA Standards• TIA‐568.3: “Optical Fiber Cabling and Components Standard”– Section 7: “Optical fiber transmission performance and test requirements”

– Annex C (Informative): “Guidelines for field‐testing length, loss, and polarity of optical fiber cabling”

• TIA‐526‐14‐B: “Optical power loss measurements of installed multimode fiber cable plant”

• TIA‐526‐7: “Measurement of optical power loss of installed single‐mode fiber cable plant”

Channels and Links – Applies to Fiber as Well

Optical Patch Panel

Optical Patch Panel

Equipment Equipment

Connections and splices possibleEquipment Cord Equipment Cord

Channel

Link

dB vs. dBm dBm = an ABSOLUTE measurement of power

• (1mW = 0dBm) dB = a RELATIVE measurement Loss is a Reference Measurement (not an Absolute Measurement) First step in an accurate loss measurement is performing a reference! Purpose of a reference is to “zero out” any test cables and connectors

Tx Rx

2 dB 5 dB1 mW = 0 dBm

.5 dB

Loss = 7.5 dB

-7.5 dBm

• Use high performance connectors– Optimal optical and geometrical characteristics

• Numerical aperture (NA)• Core/ferrule concentricity

• When mated with other TRCs produce near zero loss and reduces uncertainty

• Called for in various standards for loss measurements of installed fiber cabling

Test Reference Cords (TRCs)

• 1 Fiber Reference

Setting Reference – Three options:

Light Source Power MeterTest Jumper

Connect the OLTS together w/reference jumper – reference power meter (set to 0dB)


Disconnect the fiber at the power meter. Connect a test jumper to the power meter. Add couplers (channel testing) or connect to bulkhead (link testing) and connect to fiber system under test

Test JumperFiber System under Test

Coupler/Bulkhead Coupler/Bulkhead

OLTS = Optical Loss Test Set. Typically has Light Source and Power Meter at both ends. Simplex shown for clarity.



Connect the OLTS together using two test jumpers and a coupler –reference power meter (set to 0dB)

Light Source Power Meter

Test Jumper

Disconnect the fibers at the coupler and connect the system to be tested (link testing). Need to add one coupler for channel testing

Test Jumper

Test JumperCoupler


Fiber System under Test



Connect the OLTS together with two test jumpers, two couplers AND a third test jumper – reference power meter (set to 0dB)


Test Jumpers

Disconnect the fibers at the couplers, remove the third test jumperand connect system to be tested. Leave couplers in for channel testing, remove for link testing.

Test Jumpers


Test Jumpers Test JumpersTest Jumper

Couplers Couplers




Summary of Reference Methods


Test Jumpers Test Jumpers

One Fiber

Two Fiber

Three Fiber

Difference is the number of bulkhead (coupler) connections referenced out of the loss measurement.

Use the method recommended by your local standards OR by your vendor! For link testing, 1 jumper method is universally recommended

Always check your reference!Connect test jumpers together and measure lossEnsure no “gainers”Save result for proof of good reference


Multimode Launch Conditions• Different multimode light sources = different modal power distributions

(commonly referred to as launch conditions)• Launch conditions directly impact link loss measurements accuracy

– LED overfills a multimode fiber tending to overstate loss – Laser underfills a multimode fiber tending to understate loss

CoreOverfilled source (LED)

Cladding

Cladding

Higher modesLower modes

CoreUnderfilled source (Laser)

Cladding

Cladding

Lower modes

Encircled Flux (EF)• Ratio between the transmitted power at a given radius

of the fiber core and the total injected power

• Defined in IEC 61280-4-1 standard to characterize the launch conditions of MMF test sources

• Is measured at the launch cord connector – NOT at the source output

• Replaces older “launch condition” requires such as Coupled Power Ratio (CPR)

• Can be achieved by using a universal or matched modal controller (TSB-4979)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 5 10 15 20 25 30

radius (µm)

Enci

rcle

d flu

x

TSB‐4979

• Universal Controller– For legacy sources– Adds a “black box” to the output of the legacy source

• Matched Controller– Specific source matched with specific launch cord– Launch cord may have additional conditioning

Legacy Source Black Box

Universal Controller

Specific Source Black Box

Matched Controller

Launch Cord

• Use feet/meter markings on fiber jacket

• Physically measure

• Use a tester that measures length– Typically using propagation delay and refractive index

Measuring Length

• Acceptable loss is based on several factors:– Number of connections – Number of splices– Loss per Km (at specific

wavelengths)– Regional or vendor

requirements

Loss Limits• Maximum allowable losses

(TIA)– Loss per connection = 0.75 dB– Loss per splice= 0.3dB– Loss per Km (slope)

• 850nm = 3.5 dB• 1300nm = 1.5 dB• 1310 nm = 1.0 dB• 1550 nm = 1.0 dBFor Tier 1 Certification the user must

tell the OLTS how many connections and splices are in the fiber system under test

• One Fiber Reference• 2 connections (default for one fiber reference)• No splices• 300 meters of MMF• Loss limit at 850nm:

– 0.75 dB per connector 1.5dB– 300 meters (3.5 dB per km) 1.05dB– Total 2.55 dB

• Loss limit at 1300nm:– 0.75 dB per connector 1.5dB– 300 meters (1.5 dB per km) 0.45dB– Total 1.95dB

Tier 1 Fiber Certification Example

Limit is based on settingsLoss is measuredMargin in calculated

• In this context, application is the protocol that will “ride” on the fiber.– Typically Ethernet or Fiber Channel

• What is the connection between the “limit” on the previous slide and what the application requires?– Very little…

Will My Application Actually Work?

Cable Type 1GbE 10GbE 40 /100GbE

Loss (dB) Length (m) Loss (dB) Length (m) Loss (dB) Length (m)

OM3 4.5 1000 2.6 300 1.9 100

OM4 4.8 1100 3.1 1100 1.5 150

Loss and Length Limits at 850nm

• Most Enterprise Optical Loss Test Sets will report “Compliant Networks” based on loss measurement

• Cautions! –– Can “PASS” generic limit, but have too much

loss for specific application– Most testing performed is on links – but

applications run on channels• If the Application to be carried on the fiber is

known, use Application (Network) limit

Compliant Networks

Ensure Your Results Are Accurate and Consistent1. Treat your test reference jumpers AND the fiber under test with respect

– inspect and clean ALL fibers ALL the time• Inspect Before You ConnectSM• IEC 61300‐3‐35 Certification

2. Understand reference methods and their impact on limit, loss, and margin

• Reference method chosen in tester setup is correct and matches actual physical setup

• Check the reference often3. Understand your multimode launch condition and have a plan to move

to Encircled Flux• Standard modal power distribution = consistent loss results between testers

4. Complement your Tier 1 certification with Tier 2 certification

Top 5 errors in OTDR (Tier 2) testing

Adrian Young, Fluke Networks

Top five in no specific order

1. Failing to use a launch fiber2. Adding a short adapter cable to the launch fiber3. Using only a launch fiber4. Failing to verify launch fiber5. Incorrect test limit

Failing to use a launch fiber• The OTDR receiver needs time to settle after the OTDR port• If you use a patch cord 2.1 m (7 ft.)

– The first event/connection will be missed– The OTDR may or may not complain

Adapter cable added• You’re testing LC links and all you have is an SC to SC launch fiber

• So the easiest solution is to add a short SC to LC cord on the end of the launch fiber

SC SC LC LC LC

Two connections will be measured as a single loss event, which can result in failing a good link

LaunchFiber

Using only a launch fiber• As a guide, the launch fiber should be

– 100 m (328 ft.) for multimode– 130 m (427 ft.) for singlemode (good for links to ≈ 27 km / 16.8 miles)

-0.30 dB ? dB

LaunchFiber

Failing to verify the launch fibers• If you only use a launch fiber, how do you know if it is good?• Poor launch fibers represent the majority of support calls

How good is this connector? You don’t know!? dB

LaunchFiber

Failing to verify the launch fibers• If you use a launch and tail fiber, you can verify them before testing

• Poor launch fibers represent the majority of support calls

LaunchFiber

Tail (Receive)Fiber

Using a tail fiber• With a tail fiber, the connection at the far end is now characterized

• Requires a technician to be at the far end– Most common objection to doing this

LaunchFiber

Tail (Receive)Fiber

-0.30 dB 0.80 dB

Testing in one direction only?• Is that really a fail at connection ?

– Event limit set to 0.75 dB

-0.30 dB 0.80 dB

LaunchFiber

Tail (Receive)Fiber

Testing in one direction only?• Tested in the other direction, it now fails at connection !

– Event limit set to 0.75 dB

0.90 dB -0.37 dB

LaunchFiber

Tail (Receive)Fiber

Bi‐directional averaging• When bi‐directional averaging is implemented

– Mismatches in backscatter etc. between the launch/tail fibers and the fiber under test are taken out, mathematically speaking

0.90 dB -0.37 dB

-0.30 dB 0.80 dB

Bi‐directional averaging• When bi‐directional averaging is implemented

– Mismatches in backscatter etc. between the launch/tail fibers and the fiber under test are taken out, mathematically speaking

0.30 dB 0.22 dB

Wrong test limit• OTDR loss event measurements heavily rely on good reflectance• Poor reflectance can result in

– Optimistic / negative loss readings– Errors when the application runs

• Agree on a reflectance limit• As a guide (talk to your vendor)

– ‐35 dB for multimode– ‐40 dB for singlemode– ‐55 dB for APC singlemode Same link tested

No reflectance limit Reflectance limit -35 dB

Questions?

106

• Rodney Casteel ([email protected])• Robert Reid ([email protected])• Adrian Young ([email protected])• Ed Gastle ([email protected])• Lee Kellett ([email protected])

Documents

New Requirements in Acceptance Testing for Fiber Installations · IEEE 802.3ba: 40/100G Ethernet Approved (June 2010) 10G 40G 100G Approach Laser Type Fiber Type Connector Transceiver