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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