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Optical Fiber Data Center Field Testing
ANSI/BICSI 002-2011 Data Center Design and Implementation Best Practices
• 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
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• 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
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• Laser Eye Safety
• Fiber Scrap – Shards from fiber prep
• Puncture and Cut issues
• Ensuring all systems are off
Fiber Safety Issues
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
• Diagnose, repair, and verify optical networks after activation
Standards and Requirements
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Data Center Requirements
TIA 942-A Data Center Standard
7 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
• Length restriction is now application based
Data Center Requirements
ANSI/BICSI 002-2011 Data Center Design and Implementation Best Practices
8 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
• VFL: Polarity
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
Link Certification Tests and Test Equipment
What test equipment options do I have?
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Va
lue
/ F
ea
ture
s
Product category
Visual Fault
Locators/Inspection
VFI’s
MT Tracer
Light Source
Power Meter
LS/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
The Connector End-Face Inspection
• 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
Live Image Snapshot Image Review
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)
● Fiber polarity check
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
16 Source: Opticonx
Method A
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
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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
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Data Center Testing
Tier 1 & Tier 2
Required and Recommended
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
Certification Test Set
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?
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• 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
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• 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
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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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What’s important to look for in an OTDR
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
components in a fiber system and identify them as Events
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
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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
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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
Event = Connection (C), Splice (S) or other anomaly in the fiber system
• 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
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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)
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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
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