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: – [email protected] – 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