Testing and troubleshooting enterprise fiber-optic cabling

Presenter:

Neftali Usabal

Fluke Networks - LATAM

Agenda

• Testing Methods and Standards

– Why we test optical systems

– Terminology & types of testing

– Standards based testing requirements

• Cleaning and Inspection

• Attenuation (loss)Testing Overview (Tier 1)

• OTDR Testing Overview (Tier 2)

CERTIFICATION TESTING OF OPTICAL CABLING

• Product acceptance upon receipt

• Installation Acceptance following

deployment of system

• Accounting/Documentation of your

system for:

– As Built records

– Performance Benchmarking

– MAC & Rework

• Proof/Verification that the final system

meets design specifications and

contractual obligations

Efficient and properly performed certification testing will ensure that you get paid fast and avoid callbacks!

Factors Affecting Signal Loss

• Intrinsic

• Splice Loss (non reflective event)

• Connector Loss (reflective event)

• Macrobending

• Microbending

Factors Affecting Performance

• Chromatic Dispersion (Singlemode Fibers)

• Polarization Mode Dispersion (Singlemode Fibers)

• Modal Dispersion (Multimode Fibers)

Dispersion or pulse broadening

Testing Standards

• ANSI/TIA/568-C.1 — Commercial Building Telecommunications Cabling Standard.

• ANSI/TIA/568-C.3

— Optical Fiber Cabling and Components Standard. Includes guidelines for Field-Testing Length, Loss and Polarity of Optical Fiber Cabling Systems

• ANSI/TIA/-526-14-A

— OFSTP-14A Optical Power Loss Measurement of Installed Multimode Fiber Cable Plant (ANSI/TIA/EIA-526-14A-98)

• ANSI/TIA/526-7

— OFSTP-7 Measurement of Optical Power Loss of Installed Single-mode Fiber Cable Plant (ANSI/TIA/EIA-526-7-98)

• ISO IEC 14763-3

– Defines testing methods and limits including definition of “test Reference Cords” • TIA/TSB 4979 Methods for meeting Encircled Flux launch conditions

• Titled: – Generic Telecommunications Cabling for Customer Premises –

Addendum 2, General Updates

– Published August 2012

• New application limits – 40GBASE-SR4 (100 m, 1.9 dB over OM3)

– 40GBASE-SR4 (150 m, 1.5 dB over OM4)

– 100GBASE-SR10 (100 m, 1.9 dB over OM3)

– 100GBASE-SR10 (150 m, 1.5 dB over OM4)

• Limits are getting tighter, CPR and MPD no longer good enough

ANSI/TIA-568-C.0-2

• Was considered adequate for the time (2003)

• Test limits getting tighter – 1000BASE-SX (2.6 dB over OM1)

– 10GBASE-SR (2.6 dB over OM3)

– Consultants tightening loss budgets

– Manufacturers tightening loss budgets

• ISO/IEC 14763-3 (2006) changed to MPD – Modal Power Distribution

– Tighter than CPR

– Now also adopting Encircled Flux to replace MPD

ANSI/TIA-526-14-A

• Replaced with ANSI/TIA-526-14-B (Oct 2010) titled:

– Optical Power Loss Measurements of Installed Multimode Fiber Cable Plant

• Replaced Coupled Power Ratio with Encircled Flux

– More to come on this later!

ANSI/TIA-526-14-A (2003)

Optical Test Equipment Summary

Type of

Test Equipment Investment Used For Required Tests For

Visual VFL,

Microscope, $300 - $4000 Verification Rarely

Continuity, Polarity,

Cleanliness

Power &

Attenuation

Power

Meter $1K -$5k

Verification to

manually

determined loss

budgets

Sometimes

as proxy for

Tier 1

Power, loss,

continuity, polarity

Attenuation

Testing

(Tier 1)

Optical

LossTest

Set (OLTS)

$6K - $13K

Certification to

performance

standards

Always

End -to – end Loss,

Continuity, length

polarity & compares

to performance

standards

OTDR

(Tier 2) OTDR $8K - $17K

Certification &

Troubleshooting

to ensure

installation

workmanship

Typical

Analyzes Events

(splice & connector)

by measuring

reflectance

12

Fiber inspection and cleaning

13

#1 Problem: Dirt!

• Contaminated connector end-faces: Leading cause of fiber link failures

• Particles of dust and debris trapped between fiber end faces cause signal loss, back reflection, and damaged equipment

• Many Sources of contamination: • Equipment rooms & Telecommunication rooms in filthy environments • Improper or insufficient cleaning tools, materials, procedures • Debris and corrosion from poor quality adapter sleeves • Hands of technicians • Airborne

14

Why Bother Inspecting End Faces?

• To Prevent Damage • Debris will embed in glass when contaminated connectors are mated

• When embedded debris is removed, pit remains in glass as permanent damage

• Pits cause signal loss and back reflection

• Debris causes other damage such as chips and scratches

Good Connector

Fingerprint

on Connector

Dirty Connector

Inspection images

Real images as captured from the Fluke Networks Fiber Inspector™

COMMON MISCONCEPTIONS

• Protective caps keep end-faces clean - NO

– Caps are a source of contamination: mold-release compound from manufacturing

– End-faces are NOT clean when they come pre-terminated from the factory in a sealed bag

• Canned air will blast away dirt - NO

– Is ineffective on smaller, static-charged particles

– Blows larger particles around rather than removing them

– Is ineffective on oils and compound contaminants

• Isopropyl alcohol (IPA) is the best solvent – NO

– IPA does not work on non-polar contaminants

Pulling lubricants, buffer gels, etc.

– IPA leaves a residue when not used properly

Cleaning with IBC Cleaners

• IBC™ OneClick Cleaners for cleaning different end faces/connectors — no training required

• 1.25 mm LC and MU connector and end faces

• 2.5 mm SC, ST, FC, E2000 connector and end faces

• MPO/MTP connector and end faces

• Cleans Ports on devices and patch panels as well as Cords ….with an adapter

• Dry cleaning is less efficient for cleaning grease (dried skin oil) than wet cleaning with a solvent and swabs/cleaning cubes

CLEANING WITH SOLVENT PEN

• Start with a clean, lint-free wiping surface every time

– Material left exposed accumulates ambient dust

– Material used once should not be used again

• Use a minimal amount of specialized solvent

– Important that solvent be removed after cleaning

– Move the end-face from the wet spot into a dry zone

Cleaning with a saturated wipe will not fully remove solvent

Cleaning with a dry wipe will not dissolve contaminants and can generate static, attracting dust

• Proper handling and motion

– Apply gentle pressure with soft backing behind cleaning surface

– Hold end-face perpendicular to cleaning surface

– No figure-8 motion as that’s for polishing only

• Inspect both end-faces of any connection before insertion

– If the first cleaning was not sufficient, then clean again until all contamination is removed

Company Confidential

Hands ON - Fiber Inspection

• Tap TOOLS

• Tap FiberInspector

• Focus the image with the knob

on the probe

• Press to “pause” or enter

the “still” mode

Company Confidential

Hands On: Fiber Inspection

• Tap SCALE ON

• Tap NEXT SCALE

• Drag fiber to center of scales

• Zoom on image

• Tap GRADE

• Tap GRADE again

Optical Loss Testing

• Double Ended Test – Absolute Loss measurement

• Compares Loss to industry standards – Pass/Fail Results

• Other helpful Capabilities – Length measurement – Project/Loss budget Wizard – Two fibers at a time – Bidirectional testing – Set Referencing Wizard

Tier 1 Fiber Certification with OLTS

These things must be done correctly!

• Use good/clean Test Reference Cords – ISO/IEC 14763-3 (2006)

– Reference grade connectors were required – Multimode ≤ 0.10 dB

– Singlemode ≤ 0.20 dB

• Set Reference correctly!! – Helps minimize uncertainty

– Eliminates “negative loss” incidents

• Proper Launch Conditions – Encircled Flux Per TSB 4979

Managing Uncertainty

• In ISO/IEC 14763-3 (2006), cords were recognized as a source of great uncertainty

• This standard reduced uncertainty by defining the performance of the test cord connector

• Reference grade connectors were required – Multimode ≤ 0.10 dB

– Singlemode ≤ 0.20 dB

Impact of test reference cords

0.75 dB 0.10 dB

≤ 0.30 dB

0.75 dB 0.20 dB

≤ 0.50 dB

• Sadly, most folks are setting a reference this way

• Issues – You have no idea what the loss is in the adapter

– Whatever it is, it’s subtracted from your measurement

– The uncertainty is horrendous – negative loss

Setting a Reference…What is done today

? dB

• So you end up with this

• Issues – You have no idea what the loss is in the adapter

– Whatever it is, it’s subtracted from your measurement

– The uncertainty is horrendous – negative loss

What is done today

x dB z dB

y dB

Measurement = x + y + z - ?

• Let’s take an example

• Issues – You have no idea what the loss is in the adapter

– Whatever it is, it’s subtracted from your measurement

– The uncertainty is horrendous – negative loss

What is done today

0.75 dB

• Let’s take an example

• Issues – You have no idea what the loss is in the adapter

– Whatever it is, it’s subtracted from your measurement

– The uncertainty is horrendous – negative loss

What is done today

0.3 dB 0.3 dB

0.1 dB

Measurement = 0.3 + 0.1 + 0.3 – 0.75 = -0.05 dB

• ANSI/TIA describes this as Method A

• Not for enterprise cabling systems – Used in long haul measurements

– Uncertainty of one connector not considered critical?

What is done today

? dB

• For testing an installed fiber optical link, should always use the 1 Jumper Reference Method

• Does require the test equipment to have interchangeable adapters on the INPUT ports

What is done today

• It’s ok to remove the fiber from the input ports

• You cannot remove the fiber from the output port, doing so will invalidate the reference you just made

Removed from INPUT port only

• To the INPUT ports

Connect known good cord

• To the INPUT ports

Connect known good cord

• How do I know if those cords are good?

Connect known good cord

• Connect them together using a singlemode adapter and measure the loss

Verifying the cords

ISO/IEC 14763-3 • ≤ 0.1 dB for Multimode • ≤ 0.2 dB for Singlemode ANSI/TIA-568-C.0 • ≤ 0.75 dB?

Cabling Vendors • ≤ 0.50 dB?

Why not save this as proof of good test reference cords?

*

* This can be up to 0.15 dB for LC

• ISO/IEC 14763-3 – 1 Jumper method (0.1 dB for Multimode and 0.2 dB for Singlemode)

• ANSI/TIA-568-C.0 – Does not call out test reference cord values (≤ 0.75 dB?)

– You are expected to specify this

–

• Require documentation of TRCs

Test Reference Cord Values

?

Disconnect

• ANSI/TIA-568-C.0

• First and last connections ≤ 0.75 dB

• All other connections ≤ 0.75 dB

Connect to the fiber optic link

≤ 0.75 dB ≤ 0.75 dB

• Diagrams shown to visualize the issue as best as possible

Launch conditions

Source 1 Over filled

Source 2 Under filled

EF assessment improvement

Source 1 Over filled

Source 2 Under filled

EF specifies power throughout core using multiple control radii.

EF provides tight tolerance on mode power distribution in the outer radii enabling improved agreement between EF-compliant test instruments.

• Titled: – Practical Considerations for Implementation of Multimode Launch

Conditions in the Field

• TSB = Telecommunications System Bulletin – Not an official standard

– An advisory document

– Chances are will end up in ANSI/TIA-568-D.3

• Helps users understand Encircled Flux and the options for implementing it

TIA-TSB-4979

• Option 1

– Use an external mode controller

– Replaces the mandrels

Practical implementation of EF

• Option 2 -Matched source and test reference cord

Practical implementation of EF

• At a minimum, use a mandrel – This does not yield the controlled launch

condition the industry desires that is Encircled Flux

• Don’t use a VCSEL source – Too much variability – Not standards compliant

• Consider investing in fiber optic test equipment that allows a 1 Jumper Reference – reduced uncertainty

• Verify your Test Reference Cords – Save the results and make it part of your

documentation

• If Encircled Flux is a contractual requirement, or you care about getting as many “passes” as possible: – Reference TIA/TSB 4979

• EF Mode Controllers • DTX-EFM2 • CertiFiber Pro

Tier 1 Fiber Certification Summary

46

OTDR TEsting

What is An OTDR?

-OptiFiber Pro OTDR

10.6 x 5.0 x 2.5

inches

5.7 inches

touchscreen display Taptive ™

gesture based

user interface

EventMap 8-hour battery life

Singlemode,

Multimode and

Quad modules

48

What Does An OTDR Do?

OTDR Port

Connector

Processing

& Control

Color

Display

Directional

Coupler

Very Sensitive

Photo

Detector

Two

Laser

Diodes

• Sends pulses of light out

• Keeps checking for

reflected light

• The farther the light goes,

the more time it takes to

come back

• When light hits a

connection, an extra spike

of light reflects back

• The farther the light goes,

the more loss it encounters,

so less comes back

(measures length)

(measures fiber loss)

(finds connections)

OTDR

Fiber

Under

Test

Optical Fiber

Electrical

49

OTDR in Action

The OTDR measures reflected energy and

NOT the transmitted light level.

Distance

Loss

50

OTDR Technology

• Rayleigh Scattering

• Fresnel Reflection

51

Scattering, (Rayleigh Scattering) occurs when transmitted light energy is higher than what the glass molecules can absorb and the energy is released in all directions. It is the major loss factor in fiber.

Backscattering occurs from about 0.0001% of the light being reflected back to the OTDR.

Rayleigh Scattering

52

Coupling loss air gap causes loss of light transmitted

Fresnel Reflection occurs when light traveling in one material encounters a different density material (like air). Up to 8% of the light is reflected back to the source while the rest continues out of the material.

Fresnel Reflection

What is reflectance?

An air gap between the end faces of a fiber also cause Fresnel reflections to occur.

What do those numbers mean? Reflectance is the preferred term when characterizing a single connector.

• It is a measure of the amount of power reflected by a connection.

• It includes one connector

• It is always negative.

• Smaller is better (e.g. -35dB is better than -20dB)

Refl 10logPreflected

Pincident

Return Loss is the preferred term when characterizing an entire link • It is a measure of the amount of power NOT reflected by a link.

• Includes all connections and fiber

• It is always positive.

• Bigger is better (e.g. +35dB is better than +20dB)

reflected

incident

P

Plog10ORL

Why should you care?

High reflectance causes increased Bit Error Rates (CRC errors) on the network

56

What Do OTDR Test RESULTS Look Like?

Test Example: Tier 2 (OTDR) TR

MC X

X X X

Backbone Cables

Horizontal Cables

OTDR characterizes link details

58

EventMAP & EVENT Table from OTDR

EventMap Event Table

EVENTMAP

• Easy to understand map of the

physical infrastructure

• Icons represent events.

• Passing reflective event

• Failing reflective event

• Hidden reflective event

• Passing loss event

• Failing loss event

• Hidden event’s loss is added to

previous event’s loss

60

Typical OTDR TEST RESULT

Backscatter

Reflection

61

Reflective Event

Connector

62

Loss Event

Non-reflective event

Splice or severe bend

63

End Event

End of Fiber

64

Gainer Event

50 micron fiber connected to a 62.5 micron fiber

Gainer

65

GHOST EVENT

Ghosts

66

Dynamic Range

• Determines the length of fiber that can be tested

• Provided as a dB value

• Larger values mean longer distance (typically for telcos) … and a larger dead zone

• Premises OTDR’s do not need a large dynamic range … and benefit with a small dead zone

• Pulse needs to be wide enough to get to the end of the fiber

67

Dynamic Range

Measurement

Dynamic

Range

Initial backscatter level at OTDR front connector

Dynamic range is the maximum attenuation level that the test

equipment can recognize and therefore may be used to

determine how long of a fiber can be measured.

Noise

dB

Length 0

0

68

Dead Zone

• A dead zone is like when your eyes need to recover from looking at the bright sun or the flash of a camera

• It can be reduced by using a lower pulse width, but it will decrease the dynamic range.

69

Two Types of Dead Zones

• Typically occurs in a trace whenever there is a connector

• The OTDR receiver goes “blind” from the strong reflection

• Includes duration of the reflection and recovery time for the receiver.

Event

dead zone

Attenuation

dead zone

Attenuation Dead Zone vs. Event Dead Zone • Event Dead Zone is the minimum distance the

OTDR can detect an event after the preceding event

• OFP Typical Event Dead Zone is:

• 0.5m @ 850 nm, 3 ns, -40 dB Reflectance

• 0.7m @ 1300 nm, 3 ns -40 dB Reflectance

• 0.6m @ 1310 nm, 3 ns, -50 dB Reflectance

• 0.6 m @ 1550 nm, 3 ns, -50 dB Reflectance

Attenuation Dead Zone vs. Event Dead Zone

• Attenuation Dead Zone is the minimum distance between two events on an OTDR where the OTDR can assess the event loss

• OFP Typical Attenuation Dead Zone is:

• 2.2m @ 850 nm, 3 ns, -40 dB Reflectance

• 4.5m @ 1300 nm, 3 ns -40 dB Reflectance

• 3.6m @ 1310 nm, 3 ns, -50 dB Reflectance

• 3.6 m @ 1550 nm, 3 ns, -50 dB Reflectance

72

Using a LAUNCH AND TAIL Fiber

Launch

Fiber

Will give loss of the

first connector

Tail

Fiber

Will give loss of the

last connector

73

Launch & TAIL Fiber

• A must for measuring the loss of the first and last connector in a fiber link

• Launch fiber must be significantly longer than the attenuation dead zone of the OTDR

• With short dead zones you can use a short launch fiber

74

Launch Fiber Compensation

Getting to Systems Acceptance

• Verification Testing – Typically performed after MC,

IC and / or HC connector installation

– Improves attenuation testing time

• Attenuation Testing – Final System Verification – Certifies Loss is within

Performance Standard requirements

• OTDR Testing – Tests links and point

discontinuities

Support Resources

• Knowledge Base: – http://myaccount.flukenetworks.com/f

net/en-us/supportAndDownloads/kb

• Technical Assistance Center 24 x 7 assistance: – support@flukenetworks.com – USA: 1-800-283-5853

• Resources for “Experts” – Designers:

http://www.flukenetworks.com/expertise/role/Architects-Consultants-Designers

– Installers: http://www.flukenetworks.com/expertise/role/guide-to-contract-installers-and-installation