Back to the Basics - Fiber Optic Fundamentals and Best ... · Back i ib ik to Basics: Fiber Optic Fundamentals and Best ... – 300m (OM3) or 400m (OM4) vs. 100/150 for Std –SR4

k i ib iBack to Basics: Fiber Optic Fundamentals and Best PracticesFundamentals and Best Practices

Rodney Casteel RCDD/NTS/OSP, CommScope, Chair TIA FOTC

Adrian Young, Fluke, FOTC Standards Co-ChairAdrian Young, Fluke, FOTC Standards Co Chair

Robert Reid, Panduit

Matt Brown, JDSU

Lee Kellett AFLLee Kellett, AFL

Agenda• Who Is FOTC – Rodney Casteel

• Standards Update – Matt Brownp

• 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

Matt Brown– Matt Brown

• Final Questions

Fiber Optics Technology ConsortiumOverview:

f h l i i d i i• Part of the Telecommunications Industry Association (www.tiaonline.org)

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

• Formed 20 years agoy g• Mission: to educate users about the benefits of deploying fiber in

customer-owned networks• FOTC provides vendor neutral information• FOTC provides vendor-neutral information

Fiber Optics Technology Consortium

Current Members

• 3M• AFL

• Leviton• OFS

• Corning• CommScope

Fl k N t k

• Panduit• Sumitomo Electric Lightwave

S i E• Fluke Networks• General Cable• JDSU

• Superior Essex• TE Connectivity

www.tiafotc.org TIA Fiber Optics Technology Consortium

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• Speak at industry conferences like BICSI

• Contribute to industry publications – check out our article on Making Networks Greener in BICSI News.Making Networks Greener in BICSI News.

• Conducting market research

Fiber Optics Technology Consortium• Recent Webinars Available on Demand

– LAN Standards, News & Trends: 2014 UpdateP Li k T i f MPO C bl Pl f Hi h S d– Permanent Link Testing of MPO Cable Plant for Higher Speed Channels

– Fiber Optic Connectors, Designs, Applications & Choices

• 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 CECwebinar and want to receive your CEC.

www.tiafotc.org TIA Fiber Optics Technology Consortium

Standards Update

Matt Brown

JDSU

Standards Update (TIA)

568 3 O ti l fib bli d t t d d• 568.3 – Optical fiber cabling and component standard• Being updated to revision “D” – along with 568.0 and 568.1• Transmission performance and test requirements will be in Clause 7Transmission performance and test requirements will be in Clause 7• Annex D will provide guidelines for field testing• Task group established to review and update Clause 7 and Annex D

Higher Speed Channels

Rodney Casteel RCDD/NTS/OSP 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(Approximately 3 devices and/or connections per person on the

planet)

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

• 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

18

16 15.9 EB16

14

1210 8 EB

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

10

8 7.0 EB

10.8 EB

“Cisco VNI: Forecast and Methodology,

2013-2018"February 2014

6

42.6 EB

4.4 EB

2

01.5 EB

2013 2014 2015 2016 2017 2018

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

Gl b l Cl d IP t ffi ill t f t thi d f t t l• 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

Storage RequirementsGl b l i f h h 2020

40

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

Global storage capacity forecast through 202040.00

30

25

ytes

(ZB

)

By 2020 the average person will maintain

20

15

10

Zeta

b

7 23By 2020 the average person will maintain 130 terabytes of personal data. 5

02012 2020

2.59

7.23

2017

Source: Cisco IBSG

Source: IDC

2012 20202017

Data center emerging trends

Cloud Virtualized Green

Big Data ConvergedDCIMSDN

EthernetInfinibandFCoE

iSCSi Fibre Channel

C bli I f t t i t th f i l t tiCabling Infrastructure impacts the success of implementation

Changing infrastructure requirements for the data center

Density ScalabilityBandwidth Manageability

The cloud and physical infrastructure

L3

L2


L3

L2


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

• Scalable infrastructure essential

Traditional Data Center Cabling Infrastructure

Core Layer

Aggregation Layer

Access LayerAccess Layer

Reference Architecture

Fiber/CopperPatching

(includes FC network)

ConsoleServer

Fiber PatchingAggregation

Switch Access Switch

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

(includes FC network) Switch Access Switch

Core Switch Main Distribution Area

Core SwitchServer Row Equipment Distribution Area Main Distribution Area

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 switchesand spine switches

• Any to any concept

Pre-terminated cabling: Scalable and Quick

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

Installation time dramatically reduced

times faster than field term

• Reduces deployment risk

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

• Minimal packaging and waste on site -GREEN

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

10G 40G 100GApproach 10G x4 10G x1010G

Laser Type

Fiber Type

Connector

VCSEL Array

OM3/OM4

MPO

VCSEL Array

OM3/OM4

MPO x 2

VCSEL

OM3/OM4

LC x2Connector

# of Fibers12

MPO x 2

24

C

2

Transceiver Tolerances

MaximumDistance

Relaxed(to lower cost)

OM3: 100+ m*OM4: 125 – 150 m*

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

OM4: 125 – 150 m*

Tight

OM3: 300mOM4: 550m

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

40GBASE-eSR4 QSFP+Emerging Defacto Standardg g

• “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%

f d ( )– Lower OPEX – 50% of power dissipation (1.5W vs. 3.5W)

Cisco QSFP40G BiDi

• 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 100– OM3 – 100m

– OM4 – 125m

Serial Duplex Cable PlantTransmission Example - 10GBASE-SRp

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

“Parallel Optics” Cable Plant - Parallel Transmission Example - 40GBASE-SR4p

Type-B:1-1 array patch cord

ositi

on:

ost R

x Type-B:1-1 array patch cord


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on:

ost R

x

Type-B1-1array cable


ral s

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l tra

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o





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oLa

tele

ft mLa

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ft m

Example optical pathExample optical pathExample optical path

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

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

Key-up to key-upmated connections

PUSH

PULL

Position 1

BPUSH

PULL

PUSH

PULL

Position 1

P iti 12

Position 12

P iti 1

Transceiver

:

RxRx

RxRx

:


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:


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BBPUSH

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Position 12

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Transceiver

:

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RxRx

:

Transceiver

:

RxRx

RxRx

::

RxRx

RxRx

:

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PULL

Position 1

Position 12

Position 12

Type-B:1-1 array patch cords

B

Position 12 Position 1

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Position 12

Position 12

Position 1

Rx

:

TxTx

TxTx

:

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on:

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:

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on:

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Type-B:1-1array cables

array patch cords

Type-B:1-1ral s

igna

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array patch cords

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array patch cords

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:

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

Higher Speed IEEE RoadmapOngoing 802.3 Effortsg g

Parallel Optics Single-mode Duplex• 100GBASE-SR4

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

4 25G QSFP+ ith MPO

• 40GBASE-ER4– 0 to 40000m: 40G Ultra-long

reach over single-mode fiber– 4x25G QSFP+ with MPO

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

g– In support of Metro Area Networks

– Extended reach option to 40GBASE-LR4

– Same CWDM wavelengths, 20km and Un-retimed parallel optics

– 4x25G QSFP+ with MPO

• 100GBASE-PSM4

40km options

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

fiber (1310nm window)

Cabling & Application StandardsAssuring Application Complianceg pp p

Robert Reid Panduit

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

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

System Designer Uncontrolled Power Penalties

Deterministic Jitter Noise

Power Budget(7.3dB) C

8

7

Reflection Noise

Relative Intensity Noise (RIN)

Mode Partition Noise (MPN)

CMargin6

5 ( )

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

Margin (Headroom) = 0.8dBBCILCIL

4

System Designer Controlled Power Penalties

Channel Insertion Loss (CIL) = 2.6dB

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

3

2

Inter-symbol interference (ISI) = 3.02dB

• Both can be controlled and changed

• 75% of the Budget

AISIISI1

0

10 Gb/s MM Channel ModelISI Power Penalty - 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 example2.6dB for 10GBASE-SR channel for example

Response to current situation - Many requests for design help from customers (10G links are new to some) Typically vendors have Excel-based calculators or tabulations oflinks 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 g p

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

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

System ‘A’ - OM3 Fiber throughout with standard pigtails (0.3dB)

System ‘B’ – OM3 Fiber throughout with ‘optimized’ pigtails (0.2dB)y g p p g ( )

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 t t h dditi l htarget reach, or additional reach beyond the target

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

Channel Insertion Loss (CIL) = 1.9dB

Power Budget(8.3dB)

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

100 meter Channel

S IEEESource: IEEE

40/100G Fiber CablingLink Power Budgeting for Cabling

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

1 301.401.501.60

insertion loss total)

150 meter OM4 channel with two 0.50dB (Max.) connectors (1.0dB connector insertion loss total)0.80

0.901.001.101.201.30

or L

oss

(dB)

insertion loss total)

“Engineered Link”

0 200.300.400.500.600.70

Tota

l Con

nect

o

OM3OM4

0.100.20

100 110 120 130 140 150 160 170 180 190 200

Maximum Reach (m)Source: Panduit extrapolation from IEEE model

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

‘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)

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

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

Fiber Attenuation Max = 3.5dB/km

Link CertificationThe Importance of Link Measurement CAPABILITY

Gage R&R (Gage Repeatability and Reproducibility) is the amount of measurement variation introduced by the LSPM system, which consists of the LSPM itself and the individuals using the instrument(s). A Gage R&R study quantifies three things:

1. Repeatability - variation from the LSPM(s)2. Reproducibility - variation from the individuals using 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)

The overall Gage R&R is normally expressed as a percentage of the loss budget limits, d l f 20 30% G R&R l i id d t bl i tand a value of 20-30% Gage R&R or less is considered acceptable in most cases.

Example: for a 1.85dB loss budget (2, 0.75dB connectors & 100m of 3.5dB/km MM fiber), an acceptable Gage R&R value would be 30 percent of 1.85dB (0.6dB) or less (error of measurement standard deviation of about 0 1dB is then required)(error of measurement standard deviation of about 0.1dB is then required).

Link CertificationCAPABILITY (Precision) vs BIAS (Accuracy)

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

Types of Measurement ErrorsRepeatability and Reproducibility of Gauge

Vertical Axis is Probability of Link AcceptanceHorizontal Axis is Link LossTotal Gauge

R&R

epta

nce

mit

mit

of L

ink

Acc

e

Test

Lim

Test

Lim

Pro

babi

lity

o

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)

P

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

False Positive False Negative

Link Loss RecommendationsContractor Test Error Types

False positive…link indicates fail but truly a pass• Impacts the customer’s ability to deploy links in a timelyImpacts the customer s ability to deploy links in a timely

fashion - “Profitability Issue”False negative…link indicates pass but truly a failg p y

• Presents link reliability issues and potential warranty claims - “Day two issue”

Both types of errors are minimized by providing excellent measurement capability for application loss budgets that are

tti ti ht d ti ht d t t th t d i tgetting tighter and tighter and to support the customers desire to deploy more connectors in the channel.

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 h h l f h i bi dthat the result of the test is not biased.

There are three standard methods of completing a link loss test:

• One Jumper Method (TIA Method ‘B’)One Jumper Method (TIA Method B )

• Two Jumper Method (TIA Method ‘A’)

• Three or “Golden” Jumper Method (TIA Method ‘C’)

Both methods ‘A’ & ‘C’ have measurement ‘artifacts’ that cannot be effectively subtracted out & overall yield higher link measurement uncertainty & BIAS

ll h d “ f l ” h d d d hAll methods use “reference quality” patch cords and adapters. This ensures accurate, repeatable and reproducible measurements.

Link Loss Method Comparison

• 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 ‘A’ and ‘C’ > 1.0dB

• Method ‘A’ and Method ‘C’ are NOT recommended in links with tight• Method A and Method C are NOT recommended in links with tight application budgets (where variability presented above is a significant fraction of the link budget specification)

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

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

‘Commissioning’ Testing ‘Witness’ or Audit Testing New Testing(Contractor #1) (Customer) (With Reference Cords)

Link CertificationCustomer Example #1 – Reproducibility of Measurements

Significant Diff. in average Headroom between Audit and Commissioning permanent link loss testsloss tests

Extremely poor reproducibility > 1dB

Consumes Headroom spec.

Link CertificationCustomer Example #1 - Correlation of Measurements

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

Result - Poor relationship between tests (random) and no ability to

ff ti l di t f th theffectively predict one from the other

Link CertificationCustomer Example #2 - Contamination (Location Based Variability)

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 li k b f t ti t d)links before testing was stopped).

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

Link CertificationCustomer Example #2 - Contamination (Time Based Variability)

Out of Control In Control

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

Link CertificationCustomer Example #2 - Contamination (Location Based Variability)

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

• Systemic testing issues at play here (possibly damaged reference cords or the like)

• All discrepant links were retested with the best practices in inspection• All discrepant links were 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 (as indicated in the plot), passed ith significant headroom to the standard hen retestedwith significant headroom to the standard when retested

• This customer has since adopted these cleaning and inspection practices on reference patch cords and links under test, and this has had significant i t th i t bilit d t bilit f t iimpact on their measurement capability and stability of measurements in particular

Best PracticesConnector Inspection and CleaningConnector Inspection and Cleaning

L K ll tt AFLLee Kellett, AFL

Why Do We Care?

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

• Network failures cause downtime and truck rolls.

• These cost money... lots of money.

• Inspecting and cleaning before connecting saves p g g gtroubleshooting costs and downtime and improves performance. Period!p

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• 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 g gand cause permanent damage – cleaning will no longer helpg p

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 installationscertify installations

• Verifies pre-connectorized products have been supplied as neededsupplied as needed

• Saves time and money in the long run

What Equipment Do I Need?

• A good inspection scope – Manual/view only is ok; auto pass/fail is best

– stand alone or connected to your other test equipment

• Cleaning supplies– Dry is okDry is ok

– Wet and dry options are prefered

– Make sure they are designed for fiber – tissues don’t– Make sure they are designed for fiber tissues don t work!

Reality Check

WHAT WE HEAR...

I h t h d i i k

REALITY...

YIKES! Hi h d t k f• I have not had issues – a quick rub on my shirt works

• YIKES! High speed networks of today are not forgiving – NEED clean, low loss connections

• I cleaned – no need to inspect • If there are issues – how will you prove it was not you? How do you know for sure?

• It takes too much time – not h i

you know for sure?

• How much does it cost to replace connectors? How much

worth itp

does a truck roll cost?

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 cleaningp g g

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

Best Practices - Summary

• Inspect, Clean and Inspect every connectorAssures optimum performance– Assures optimum performance

– Prevents damage

S ti d i th bi i t l d ti– Saves time and money in the big picture – less downtime, fewer truck rolls, less damage and replacement

Ass res performance needs ill be met– Assures performance needs will be met

– Provides a better product to your customers

TIER 1 CERTIFICATIONTI R C RTIFICATION

M tt B JDSUMatt Brown, JDSU

What is Tier 1 Fiber Certification?

• Tier 1 Fiber Certification:• Measure Length• Measure Length

• Measure Loss

Ch k P l it• Check Polarity

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

l• Document results

A Consistency Challenge

T h A T h BTech ATester A

Tech BTester A

If different results –different best practices

Tech ATester B

Tech BTester BTester B Tester B

A Consistency Challenge

T h A T h BTech ATester A

Tech BTester A

If different results –different tester specifications

Tech ATester B

Tech BTester BTester B Tester B

Leading Causes of Inconsistent Results1. Fiber end-face condition

Covered already– Covered already2. Reference method selected matches

h i l fi ti d lphysical configuration and was properly performed

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

A Brief Note on StandardsThe wonderful thing about standards…

…is there are so many to choose from!

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,Annex C (Informative): Guidelines for field testing length,

loss, and polarity of optical fiber cabling”• TIA-526-14-B: “Optical power loss measurements of

i t ll d lti d fib bl l t”installed multimode fiber cable plant• TIA-526-7: “Measurement of optical power loss of

installed single-mode fiber cable plant”installed single mode fiber cable plant

Channels and Links – Applies to Fiber as Well

Connections and splices possibleEquipment Cord Equipment Cord

Optical Patch Panel

Optical Patch P l

Equipment EquipmentPanel Panel

Link

Channel

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!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-7.5 dBm

Loss = 7.5 dB

Test Reference Cords (TRCs)• 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 When mated with other TRCs produce near ero loss and reducesuncertainty

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

Setting Reference – Three options:• 1 Fiber Reference

Connect the OLTS together w/reference jumper – reference power t ( t t 0dB)

Light Source Power MeterTest Jumper

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

Light Source Power Meter

Test Jumper

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.

Setting Reference – Three options:

Connect the OLTS together using two test jumpers and a coupler –f t ( t t 0dB)

• 2 Fiber Reference

Light Source Power MeterTest Jumper

reference power meter (set to 0dB)

Test JumperCoupler

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 JumperFiber System under Test


Setting Reference – Three options:

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

• 3 Fiber Reference

j p p ( )


T t JTest Jumper

Couplers Couplers

Disconnect the fibers at the couplers, remove the third test jumperand connect system to be tested. Leave couplers in for channel t ti f li k t ti

Test Jumpers Test Jumpers


testing, remove for link testing.

Fiber System under Test


Test Jumpers Test Jumpers

y

Summary of Reference Methods 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!

One Fiber

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

Two Fiber

Three Fiber


Test Jumpers Test JumpersFiber System under Test

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)L h diti di tl i t li k l t• 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

Higher modesLower modes Lower modes

CoreOverfilled

( )

Cladding

CladdingCore

Underfilled

Cladding

Claddingsource (LED) Claddingsource (Laser) Cladding

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

of the fiber core and the total injected power0,6

0,7

0,8

0,9

1

d flu

x

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

I d t th l h d t NOT t th0

0,1

0,2

0,3

0,4

0,5

0 5 10 15 20 25 30

radius (µm)

Enci

rcle

d

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

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

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

TSB-4979

• Universal ControllerFor legacy sources

Legacy Source Black Box

– For legacy sources

– Adds a “black box” to the output of the legacy source

M h d C ll

Universal Controller

• Matched Controller– Specific source matched with specific launch cord

– Launch cord may have additional conditioning

Specific Source Black Box

Matched Controller

Launch Cord

Measuring Length

• Use feet/meter markings on fiber jacket

• Physically measure

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

Loss Limits• Acceptable loss is based on

several factors:• Maximum allowable losses

(TIA)– Number of connections – Number of splices– Loss per Km (at specific

( )– Loss per connection = 0.75 dB– Loss per splice= 0.3dBLoss per Km (at specific

wavelengths)– Regional or vendor

requirements

– Loss per Km (slope)• 850nm = 3.5 dB• 1300nm = 1 5 dBrequirements 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 connectorstell the OLTS how many connectors and splices are in the fiber system under test

Tier 1 Fiber Certification Example• One Fiber Reference• 2 connections (default for one fiber reference)

N li• 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

Limit is based on settingsLoss is measuredMargin in calculated( p )

– Total 1.95dB

Will My Application Actually Work?• 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 littleVery little…

Cable Type 1GbE 10GbE 40 /100GbE

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

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

Compliant Networks• Most Enterprise Optical Loss Test Sets will report

“Compliant Networks” based on loss measurementmeasurement

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

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

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

known, use Application (Network) limit

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 ConnectSMspect e o e ou Co ect• 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 U d t d lti d l h diti d h l t3. 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 certification4. Complement your Tier 1 certification with Tier 2 certification

Top 5 errors in OTDR (Tier 2) testingTop 5 errors in OTDR (Tier 2) testing

Ad i Y Fl k N t kAdrian Young, Fluke Networks

Top five in no specific order

1. Failing to use a launch fiber

2 Addi h t d t bl t th l h fib2. Adding a short adapter cable to the launch fiber

3. Using only a launch fiber

4. Failing to verify launch fiber

5 Incorrect test limit5. 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 )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 callsPoor launch fibers represent the majority of support calls

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

LaunchFiber

Failing to verify the launch fibers

• If you use a launch and tail fiber, you can verify them before testingg

• 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 thisj g

-0.30 dB 0.80 dB

LaunchFiber

Tail (Receive)Fiber

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 30 dB 0 80 dB

-0.30 dB 0.80 dB

0.90 dB -0.37 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 S li k t t d

No reflectance limit Reflectance limit -35 dB

– -55 dB for APC singlemode Same link tested

Questions?

• Rodney Casteel ([email protected])

• Robert Reid ([email protected])

• Adrian Young ([email protected])

• Matt Brown([email protected])

105

• Lee Kellett ([email protected])

Documents

Back to the Basics - Fiber Optic Fundamentals and Best ... · Back i ib ik to Basics: Fiber Optic Fundamentals and Best ... – 300m (OM3) or 400m (OM4) vs. 100/150 for Std –SR4