Best Practices for Ensuring Fiber Optic System Performance Inspection, Cleaning, Testing

Best Practices for Ensuring Fiber Optic System Performance

Inspection, Cleaning, Testing

© 2008 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION2

Agenda

Fiber Optics Key Concepts– Fiber types and Connectors– Fiber Connections: the good, the bad, and the ugly– Measurement Units

Inspection and Cleaning– Inspect Before You ConnectSM

– Inspect Both Sides– Proactive Inspection– Cleaning Best Practices

Testing– Basic– Advanced


Optical Communications

Communication technology, developed in the 70s, that sends optical signals down hair-thin strands of glass fiber

Transmitter Receiver

Light Rays Fiber


Optical Fiber Types

Multimode Single-mode

2 Types


Fiber Types MM

– High attenuation– 850 to 1300 nm transmission wavelengths– Local networks (<2 km)– Limited bandwidth– LAN/Industry

Fiber carries numerous light rays (mode) simultaneously through the fiber.


Fiber Types SM

– Low attenuation– 1260 to 1660 nm transmission wavelengths– Access/medium/long haul networks (>200 km)– Nearly infinite bandwidth– Telecom/CATV– FTTx – CWDM/DWDM

Fiber carries a single light ray (mode).


Fiber Connectors are Everywhere!

Fiber optic connectors are common throughout the network as they

provide the power to add, drop, move, and change the network.

Buildings

Multi-home UnitsResidential

CO/

Headend/

MTSO

Local Convergence Point

Network Access Points

Feeder Cables

Distribution Cables

Drop Cables


Fiber Optic Connector

SC Connector

The BODY houses the ferrule to secure the fiber in place.

The FERRULE is a small cylinder used to mount the fiber and acts as the alignment mechanism. The end of the fiber is located at the end of the ferrule.

The FIBER comprises 2 layers: the CLADDING and the CORE.

– The CLADDING is a glass layer surrounding the core, which prevents the signal in the core from escaping.

– The CORE is the critical center layer of the fiber and the conduit that light passes through.

Fiber connectors have extremely tight tolerances with the potential to make a low-loss connection. To achieve this potential, they must be handled and mated properly.

BODYBODY

FERRULEFERRULE

FIBERFIBER

CLADDINGCLADDING

CORECORE


Anatomy of Fiber Connectors

Light is transmitted and retained in the CORE of the optical fiber by total internal reflection.

Single-mode Fiber StructureSingle-mode fibers carry a single ray of light, making them better in retaining the fidelity of light over long distances.

The fiber connector endface has 3 major areas – the core, the cladding and the ferrule. Particles closer to the core will have more impact than those farther out.

CORE – 9 µCORE – 9 µ

CLADDING – 125 µCLADDING – 125 µ

FERRULE – 1.25 or 2.5 mm

FERRULE – 1.25 or 2.5 mm

Fiber End Face View


Single Fiber vs. Multi-Fiber Connectors

SINGLE FIBER CONNECTOR MULTI-FIBER CONNECTOR

White ceramic ferrule One fiber per connector Common types include SC,

LC, FC, and ST

Polymer ferrule Multiple fibers in linear array

(for example, 8, 12, 24, 48, and 72) in single connector providing high-density connectivity

Common type is MPO or MTP®


Connector Types

SC Connector– 2.5 mm ferrule

– Push-pull latching mechanism

– Most widely used connector today (LAN/WAN)

FC connector– 2.5 mm ferrule

– Screw mechanism with key –aligned

– Mainly used with single-mode fibers

ST Connector– 2.5 mm ferrule

– Twist-lock mechanism

– Mainly used with multimode fibers


Connector Types

LC Connector– 1.25 mm ferrule

– Finger latch

– Fastest growing connector

E2000 Connector– 2.5 mm ferrule

– Finger latch with a protective cap over the ferrule

DIN Connector– 2.5 mm ferrule

– Anti-rotation keyed

– Used mainly in EU

MU Connector– 1.25 mm ferrule

– Push-pull latching mechanism


Types of End Faces

PC – Physical Contact APC – Angled Physical Contact

The angle reduces the back-reflection of the connection.

SC - PC SC - APC


Focus on the Connection

Bulkhead Adapter

Fiber Connector

Alignment Sleeve

Alignment Sleeve

Physical Contact

FiberFerrule


What Makes a GOOD Fiber Connection?

Perfect Core Alignment

Physical Contact

Pristine Connector Interface

The 3 basic principles that are critical to achieving an efficient fiber

optic connection are “The 3 Ps”:

Core

Cladding

CLEAN

Light Transmitted

Today’s connector design and production techniques have eliminated most of the challenges to achieving core alignment and physical contact.


What Makes a BAD Fiber Connection?

A single particle mated into the core of a fiber can cause significant back reflection, insertion loss, and even equipment damage.

Today’s connector design and production techniques have eliminated

most of the challenges to achieving core alignment and physical contact.

The remaining challenge is maintaining a pristine end face. As a result,

CONTAMINATION is the No. 1 reason for troubleshooting in optical

networks.

DIRT

Core

Cladding

Back Reflection Insertion LossLight


Measurement Units

dBm unit is decibels relative to 1 mW of power dBm is an ABSOLUTE measurement dB is a RELATIVE measurement

Relative Power (dB) =10*Log)(

)(

mWPt

mWPi

0 dBm -3 dBm -20 dBm -40 dBm

1 mW 0.5 mW 0.01 mW 0.0001 mW

Tx

Rx

2 dB

5 dB

1 mW = 0 dBm

1 dBLoss = 8 dB

-8 dBm

Absolute Power (dBm) =10*LogmW

mWPi

1

)(


Optical Loss Budget

What is the average output power of the transmitter? What is the minimum sensitivity of the receiver? The difference is the maximum amount of LOSS allowable

for the optical transmission line.

Transmitter Receiver

Light Rays Fiber


Contamination and Signal Performance

Fiber Contamination and Its Effect on Signal PerformanceCLEAN CONNECTION

Back Reflection = -67.5 dBTotal Loss = 0.250 dB

11

DIRTY CONNECTION

Back Reflection = -32.5 dBTotal Loss = 4.87 dB

33

Clean Connection vs. Dirty Connection

OTDR trace illustration of the significant decrease in signal performance after mating dirty connectors


Illustration of Particle Migration

Each time connectors are mated, particles around the core become displaced, causing them to migrate and spread across the fiber surface.

Particles larger than 5 µ usually explode and multiply upon mating.

Large particles can create barriers (air gaps) that prevent physical contact.

Particles smaller than 5 µ tend to embed into the fiber surface creating pits and chips.

11.8µ

15.1µ

10.3µ

Actual fiber end face images of particle migration

Core

Cladding


Particle Migration and Signal Performance

For each successive mating, actual dB values increase as signal performance decreases

Dirt particles near or on the fiber core significantly affect signal performance

Actual fiber end face images of particle migration

-20

-30

-40

-50

-60

-70

Baseline/Initial

Contamination

1st Mating 2nd Mating 3rd Mating

Signal Performance


Types of Contamination

Fiber end faces must be free of any contamination or defects, as shown below:

Common types of contamination and defects include the following:

Dirt Oil Pits & Chips Scratches

Single Mode Fiber


Contamination Categories

LOOSEMost contamination comes from dry particles that have fallen onto the end face or have been “placed” there during handling

BONDEDMost stubborn particles are held in place with grease, oils, or dried residue from a wet cleaning process

MATEDParticles on the end face of a connector can also become embedded into the glass if mated with another connector

CONTAMINATION MUST BE CLEANED from the end face prior to mating in order to optimize the efficiency of an optical signal or interconnect

Inspection and Cleaning


Inspect Before You Connectsm

Follow the simple “INSPECT BEFORE YOU CONNECT” process to ensure

fiber end faces are clean prior to mating connectors.


Inspect, Clean, Inspect, and Go!

Fiber inspection and cleaning are SIMPLE steps with immense benefits.

44 Connect

■ If the fiber is clean, CONNECT the connector.

NOTE: Be sure to inspect both sides (patch cord “male” and bulkhead “female”) of the fiber interconnect.

22 Clean

■ If the fiber is dirty, use a simple cleaning tool to CLEAN the fiber surface.

11 Inspect

■ Use a probe microscope to INSPECT the fiber.

– If the fiber is dirty, go to Step 2, Clean.

– If the fiber is clean, go to Step 4, Connect.

33 Re-inspect

■ Use a probe microscope to RE-INSPECT (confirm fiber is clean).

– If the fiber is still dirty, repeat Step 2, Clean.

– If the fiber is clean, go to Step 4, Connect.


Inspect and Clean Both Connectors in Pairs!

Inspecting BOTH sides of the connection is the ONLY WAY to ensure

the connector will be free of contamination and defects.

Patch cords are easy to access and view compared to the fiber inside the bulkhead (or test equipment or network equipment) which are frequently overlooked. The bulkhead side may only be half of the connection, but it is far more likely to be dirty and problematic.

Bulkhead (Female) InspectionPatch Cord (Male) Inspection


Proactive vs. Reactive Inspection

PROACTIVE INSPECTION:

Visually inspect fiber connectors at every stage of handling BEFORE mating them.

Connectors are much easier to clean prior to mating, before embedding debris into the fiber.

REACTIVE INSPECTION:

Visually inspect fiber connectors AFTER discovering a problem, typically during troubleshooting.

By this time, connectors and other equipment may have suffered permanent damage.

Dirty Fiber PRIOR to MatingFiber AFTER Mating and

Numerous Cleanings

Dirty Fiber PRIOR to

Mating

Fiber AFTER Cleaning


Benefits of Proactive Inspection

Reduce Network Downtime Active network = satisfied customers

Reduce Troubleshooting Prevent costly truck rolls and service calls

Optimize Signal PerformanceNetwork components operate at

highest level of performance

Prevent Network Damage Ensure longevity of costly network equipment

PROACTIVE INSPECTION is quick and

easy, with indisputable benefits


Cleaning Best Practices

Many tools exist to clean fiber Many companies have their own “best practices” Dry clean first. If that does not clean, then try wet

cleaning. Always finish with dry cleaning!

Testing


Test!

Basic Tests– Visual Fault Locator (VFL)– Optical Insertion Loss– Optical Power Levels

Advanced Tests– Optical Return Loss (ORL)– Optical Time Domain Reflectometer (OTDR)– Chromatic Dispersion (CD)– Polarization Mode Dispersion (PMD)– Optical Spectral Analysis (OSA)


Visual Fault Locator

VFLs provide a visible red light source useful for identifying fiber locations, detecting faults due to bending or poor connectorization, and to confirming continuity.

VFL sources can be modulated in a number of formats to help identify the correct VFL (where a number of VFL tests may be performed).


Insertion Loss

Single Direction Insertion Loss Measurement with a Source and Power Meter

Light Source

Power Meter

Reference Measurement

Light Source

Power Meter

Insertion Loss Measurement

0dB

-1.5dB

Reference first!

1, 2, or 3 jumper references can be performed – 2 jumper shown


Measuring Power Levels - PON/FTTx

OLP-57 wavelength selective Power Meter– Handles downstream at 1490 and 1550 nm– Handles upstream at 1310 nm– Through-mode capability (1 input + 1 output)– Burst-mode capability

1310 nm 1490 nm

1490 / 1550 nm

1310 nm

2

ONT1310 nm

Meter1

Meter2

1550 nm

Meter3

OLP-57/02 1490 / 1550 nm

OLT

OLP-57:Provides 3 power meters in one


Advanced Tests

Optical Return Loss (ORL) Optical Time Domain Reflectometer (OTDR)

– Detect, locate, and measure events at any location on the fiber link

Fiber Characterization– Determines the services that the fiber can be carry– Basic tests plus:

• Chromatic Dispersion (CD)

• Polarization Mode Dispersion (PMD)

Optical Spectrum Analysis (OSA)– Spectral analysis for Wavelength Division Multiplexing (WDM)

systems

Wrap-up


Summary

Always “INSPECT BEFORE YOU CONNECT” Correct testing of the fiber optic link is critical

– Tests range from basic VFL/OIL to advanced OTDR/PMD/CD

– Tests to perform depend on the network (For example, LAN, CATV, FTTx, Access, Metro, or Long Haul)

JDSU CommTest provides the tools and services to ensure the performance of your fiber optic system!

We are the World Leader in fiber video inspection


Fiber Inspection and Test Kits

Many different kits are available:– Inspection only– Inspection and cleaning– Inspection, cleaning, and testing

Example:– FIT-S001 (LAN/WAN) includes:

• OLS-5, OLS-6, OLP-5

• 200X Probe hardwired to HD3 display

• Various tips (ST, SC, SC-APC, LC, U25, and U12)

• Cleaning materials


Questions and Resources?

Questions & Answers www.JDSU.com/inspect for:

– Posters, – White Papers, – Reference Guide to Fiber Optic Testing– Product and Service Information

Recorded Webinar is posted to www.JDSU.com/test-webcasts

Contact Us:– [email protected]

Documents

Best Practices for Ensuring Fiber Optic System Performance Inspection, Cleaning, Testing