Optical Fiber Data Center Field Testing
• Data Centers are a growing segment of the enterprise market. Regardless of
whether the data center is an offsite company providing storage for one or
more companies or the data center is the onsite central storage facility for
an individual company the storage and access to the data is generally
mission critical.
• Downtime in a data center or time to turn-up a data center circuit can cost
significant dollars.
• The high speed networks require more stringent performance than typical
LANs.
• To be sure the data center networks will support today’s networking
applications it is important to properly clean, inspect and test optical fiber
networks.
• What tests are required and recommended for channels and links per the
ANSI/BICSI 002-2011 and other standards; End Face Inspection, Optical Loss
Testing, Polarity Verification, Optical Return Loss, and Fiber Characterization
using an OTDR with both launch and tail cords.
Abstract
• Requirements
– Cleaning and Inspection
– Tier 1 testing with an Optical Loss Test Set (OLTS)
– Polarity verification
– Length verification
– Tier 2 testing with an Optical Time Domain Reflectometer (OTDR)
• Recommendations
– Tier 2 OTDR testing
• Reflectance
• Optical Return Loss (ORL)
• Length
Outline- Data Center Testing
• Laser Eye Safety
• Fiber Scrap – Shards from fiber prep
• Puncture and Cut issues
• Ensuring all systems are off
Why is Test and Inspection important……
Causes of Optical Network Failures
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Causes of Optical Network Failures
As reported by:
Source: NTT – Advanced Technology
• Prevent, detect, & resolve leading causes of optical network failures – Contaminated, damaged, or poorly polished connectors
– Poor splices
– Micro- or Macro-bends induced in shipping or installation
• Verify quality of new optical fiber installations
Standards and Requirements
Data Center Requirements
TIA 942-A Data Center Standard
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AFL Company Confidential
•
Standardizes
•
LC connectors for 1 or 2 fibers
•
MPO connectors for more than 3 fibers
•
Removes OM1 and OM2 fiber support
•
Requires a minimum of OM3 fiber
•
Recommends OM4 fiber or single-mode
•
Eliminates the 100m horizontal cabling restriction
Data Center Requirements
ANSI/BICSI 002-2011 Data Center Design and Implementation Best Practices
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AFL Company Confidential
• Tier 1: OLTS- OPM and OLS attenuation measurement- Required
• Attenuation
• Polarity
• Length if capable
• Tier 2: OTDR measurements – Required
• Characterize Anomalies with traces
• Evaluate uniformity of connections (Loss of splices & connectors)
• Use manufacturers mean insertion loss of components to calculate link budget
• Inspection and Cleaning –Required
• Other measurements – Recommended
• OTDR: Fiber Length, Reflectance, ORL
OTDR
Connection or splice reflectivity
OTDR
Connection or splice insertion loss
OTDR
Link “baseline trace”
Tier 2 -- Going beyond the minimum TIA specs
Tier 1 -- Required
Can be verified by inspection (of cable markers) or measured using a Certification Test Set or OTDR
Link Length
OLTS or VFI (red laser)
Link Polarity
OLTS (Certification Test Set or light source and optical power meter)
Link Insertion Loss
TIA/EIA 568-C.0 Annex E
What test equipment options do I have?
10 V al u e / F eatu res Product category Visual Fault Locators/Inspection VFI’s MT Tracer Light Source Power MeterLS/PM & OLTS (Tier 1) OTDR & *OLTS (Tier 1 & *2)
Certification Test kit OTDR/ Certification Test Kit OTDR w/ Light SOurce FOCIS MPO Tester
Cleaning, Inspection and Polarity
Required
• Verify no energy with power
meter – First
• Be sure to clean both
connectors prior to mating to
prevent moving the dirt
between connectors
• One-click cleaners are easy, fast
and effective; enabling user to
clean patch cords and through
bulkheads in patch panels
• Inspect connector end-face for:
• Dirt
• Oil
• Scratches
• Epoxy
The Connector End-Face Inspection
Scratch goes near the core!
Dirt particles
Body Oil
Don’t touch the connector end-face!
Clean MPO end-face!
Inspection always required
Visual Fault Identifier/Locator (VFI/VFL)
Basic Light Test Continuity/Polarity
● Visually see breaks and faults
● Enables user to locate events that are too close together or too close to the OTDR (limited to 4 km range)
MPO Polarity check
MPO trunk cables why polarity matters
• MPO-MPO trunks are typically one of three Methods: A, B or C – Keying assures proper orientation of the MPO
– Keying does not assure proper polarity or Method
– Users should select one method for their networks to avoid polarity issues
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Source: Opticonx
MPO Polarity check
MPO trunk cables why polarity matters
• Tracer / Tester can be used to trace polarity problems
• Visible light is sequentially injected into one end of the
MPO trunk and the MT Tracer indicates which fiber it exits
MPO Polarity check
MPO trunk cables why polarity matters
• Method A
– Straight through trunks; key-up to key-down adapters
• Patch cords:
– One end A to B straight thru – One end A to A pair flipped
• Method B
– Straight through trunks; key-up to key-up adapters
• Patch cords:
– Both ends A to B straight thru
• Method C
– Pair flipped trunks; key-up to key-down adapters
• Patch cords:
– Both ends A to B straight thru
Data Center Testing
Tier 1 & Tier 2
Attenuation: Decrease in Optical Power
Insertion Loss
● Measured in decibels (dB)
● Limits the distance the signal travels
● Some attenuation is inherent in glass
● Connectors can be the single largest contributor
to attenuation in the Data Center
● Some attenuation can be induced by people and
the environment
1 0
1
0 1
1 0
0
0 1
Signal below receiver threshold
which is a ‘1’ is read as a ‘0’
Tier 1 test and OPM Applications
Use the OPM function and OLS (MM/SM light source) to…
measure link loss in
dBm/dB
measure optical
power levels of
electronics
interchangeable
adapters allow for 1
jumper reference
method
• Measures • Attenuation • Length • Checks • Continuity • Polarity • Test
• Multiple wavelengths in two directions • Two fibers at a time
• Capable of supporting end-face inspection
Tier 2 Testing and Characterization
● Generates a baseline trace
A “visual” characterization of the link
- Measure Loss
- Measure Reflectance
- Measure Optical Return Loss
- Measure Length
Fiber acceptance tool
Documentation
● Fault location tool
● Identify and evaluate specific events/problems in the link
Why use an OTDR?
• Data Centers have many connections and use short jumpers
• Very short dead-zones are required to characterize fibers and fault find
– Attenuation Dead Zone less than 3 m
– Event Dead Zone less than 1 m
What’s important to look for in an OTDR
Tools to meet Data Center Test Needs
• Easy to Use Interface such as Touch-and-TestTM
– Simple Job setup and renaming capability of results
– Auto set up modes to enable novices to get accurate and complete results – Front Panel/First Connector checks to assure a quality launch is achieved – Easy to define Launch and Tail cords which should be used to obtain link loss
measurements
• Software to help the user find installation errors
– Macro/Micro-bends – Pass/Fail Thresholds
What’s important to look for in an OTDR
Tools to meet Data Center Test Needs
Multi-functionality in a Easy-to-use platform
• OTDR
• Optical Power Meter
• Visible Fault Locator
• Support for an Inspection probe
• Documentation software
Tools to meet Data Center Test Needs
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Reflectance (-dB)
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●
Reflectance:
the ratio of reflected light to incident light at a point●
A concern in networks operating 10, 40 or 100GbE
●
Reflectance is directly impacted by termination technique
●
OTDRs best-suited to measure individual reflections of
Fresnel Reflections
(Light reflected at changes in index of refraction)
● End of a cleaved fiber
● Two mated connectors
● Un-terminated connector
● Mechanical splice
● Air gap at poorly mated connectors
Appears as a sharp spike in the waveform, OTDR trace
● Cursor positioning is important in measuring location and loss of a reflective event
● Height of a reflective event relative to backscatter is its Reflectivity
Height (dB)
How an OTDR Works
Reflectance and Optical Return Loss (-dB)
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●
Optical Return Loss (ORL):
the ratio of the average reflected light from the entire fiber, measured at the launch point, to the average incident power level injected into the fiber at the launch point● A high reflectance at the far end of a long fiber won’t contribute much to ORL
● A high reflectance at the near end of a long or short fiber will be the primary contributor to the overall ORL
How an OTDR works: Tier 2 Testing
30 Distance PIN POUT C1 S1 C3 Fiber C2 Relative Power (dB)The OTDR provides specific loss and distance measurements to
all events that are in the link
• Should be at least 100m
• Are necessary to:
– Characterize the near and far end connectors
– Provide a Link Loss Measurement
Importance of Launch and Tail Cords
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-
Documentation
Certify against Industry and/or User cabling
standards
– Pass and Fail results
– Displays headroom
Qualify network applications
Event table (OTDR)
Cable & Route Summaries
End Face Image Thumbnails
Telecommunication Industry Association
(North America)
TIA-568
International Organization for Standardization /
International Electrotechnical Commission
ISO/IEC 11801
European Committee for Electrotechnical Standardization
CENELC EN50173 ANSI/BICSI 002-2011
Data Center Design and Implementation Best Practices-
Event Type Max
Loss * (dB) Reflectance (dB) ORL (dB) Connector Multimode 0.75 - 40 (UPC) 20 Connector Singlemode 0.75 - 50 (UPC) - 60 (APC) 26 Fusion Splice 0.30 - 60
What’s Important: Cabling Standards
*For Data Center component
insertion Loss – use manufacturers values (dB)
Optical fibre type size and grade
Wavelength Fiber attenuation
coefficient (dB/km) Minimum modal bandwidth (MHz-km) Multimode 62.5µm (OM1) 850 1300 3.5 1.5 200 500 Multimode 50µm (OM2) 850 1300 3.5 1.5 200 500 Multimode 50µm (OM3) 850 1300 3.5 1.5 1500 500 Multimode 50µm (OM4) 850 1300 3.5 1.5 4700 ns Singlemode (OS1) 1310 1550 1.0 1.0 N/A N/A Singlemode (OS2) 1310 1550 1.0 1.0 N/A N/A
