fiber optic tests mark ortel sales support eng scte member and supporter

Fiber Optic Tests

Mark Ortel

Sales Support Eng

SCTE Member and Supporter

© 2010 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

Introduction to Fiber Testing


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

Inspection and Cleaning


Fiber Optic Connector

Ferrule

Cladding

CoreBody

LC CONNECTOR

Body

Houses the ferrule that secures the fiber in place

Ferrule

Thin cylinder where the fiber is mounted and acts as the fiber alignment mechanism

Fiber: Cladding

Glass layer surrounding the core, which prevents the signal in the core from escaping

Fiber: Core

The critical center layer of the fiber; the conduit that light passes through


Anatomy of Fiber Connectors

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

The fiber connector end face 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 µm (SM)CORE – 9 µm (SM)

CLADDING – 125 µmCLADDING – 125 µm

FERRULE – 1.25 or 2.5 mmFERRULE – 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®


Common Single Fiber Connectors

FC connector– 2.5 mm ferrule – Screw mechanism with key –

aligned– Legacy – mainly used with single-

mode fibers

ST Connector– 2.5 mm ferrule – Twist-lock mechanism– Legacy – mainly used with

multimode fibers

SC Connector– 2.5 mm ferrule– Push-pull latching mechanism– Most widely used connector today

(LAN/WAN)

LC Connector– 1.25 mm ferrule – Finger latch– Fastest growing connector


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


Contamination and Signal Performance

FIBER CONTAMINATION AND ITS EFFECT ON SIGNAL PERFORMANCECLEAN CONNECTION

Back Reflection = -67.5 dBTotal Loss = 0.250 dB

1

DIRTY CONNECTION

Back Reflection = -32.5 dBTotal Loss = 3.2 dB

3

CLEAN Connection vs. DIRTY Connection

This OTDR trace illustrates a significant decrease in signal performance when dirty connectors are mated.


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 µm usually explode and multiply upon mating.

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

Particles smaller than 5 µm 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


Once embedded debris is removed, pits and chips remain in the fiber.

These pits can also prevent transmission of light, causing back reflection, insertion loss and damage to other network components.

Most connectors are not inspected until the problem is detected… AFTER permanent damage has already occurred.

Mating dirty connectors embeds the debris into the fiber.

Core

Cladding

Back Reflection Insertion LossLight

DIRTPITS(permanent damage)

Mating force of 2.2 lb over 200 um diameter gives 45,000 psi.

Dirt Damages Fiber!


Types of Contamination

Fiber end faces should 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


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!

Light Transmission


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).


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

)(


Attenuation

Optical power is lost as light travels along fibers– Primarily caused by absorption and scattering– Usually expressed in dB or dB/km.

SourceSource RECEIVERRECEIVER

Pin

(Emitted power)

Pout

(Received power)

Power variation


Light scattered

Impurities

Absorption and Scattering

Absorption: Light is absorbed due to chemical properties or natural impurities in the glass. Accounts for about 5% of total loss.

Scattering is the loss of a light signal from the fiber core caused by impurities or changes in the index of refraction of the fiber. Accounts for

about 95% of total loss.

Pure Glass=Si O2

Si

SiO O O

Si

Si

O

Si

Cu

O

Imperfections


Bending Losses

Microbending – Microbending losses are due

to microscopic fiber deformations in the core-cladding interface caused by induced pressure on the glass

Macrobending – Macrobending losses are due

to physical bends in the fiber that are large in relation to fiber diameter

Attenuation due to bending is increases with wavelength (e.g. greater at 1550nm than at 1310nm)


Spectral Attenuation

1st Window

C-Band 1530 to 1565 nm (3rd window)

L-Band 1565 to 1625nm

E-Band 1360 to 1460nm

O Band 1260-1360 (2nd Window )

S- Band 1460 to 1530nm

U- Band 1625 to 1675 nm

Att

enua

tion

(dB

/km

)

Wavelength (µm)

0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7

OH-absorptionPeak

190 THz50 THz

1

2

0

3

4

5

OH-

OH-

Cut-off wavelength for singlemode fiber


Loss Process

InputOutput

Impurities

ScatteringLossInjection

Loss

AbsorptionLoss

JunctionLoss

CouplingLoss

Macro or

micro bending

lossScattering

loss


Sources

Characteristics LEDs Lasers

Output PowerLinearly proportional to drive

currentProportional to current above the

threshold

Current Drive Current: 50 to 100 mA Peak Threshold Current: 5 to 40 mA

Speed Slower Faster

Wavelengths Available 0.66 to 1.65 µm 0.78 to 1.65 µm

Spectral Width Wider (40-190 nm FWHM)Narrower (0.00001 nm to 10 nm

FWHM)

Fiber Type MM SM, MM

Ease of Use Easier Harder

Lifetime Longer Long

Cost Low High


Detectors

Photodiodes: different spectral characteristics depending on the type of semiconductor different wavelength settings/calibration in power meter

Values for temp = 0°C

Values for temp = 23°C

Si: Silicon

GE: Germanium

InGaAs: Indium Gallium Arsenide

Si GE InGaAs

Meas. Range 600 - 1000 nm 850 - 1550 nm 1000 - 1650 nm

Characteristics Only for MM fibers For general use Recommended for 1625nm

S(A/W)

850 1310 1550 (nm)

GEInGaAs

0.5

1625

Si


Dynamic Range

Difference between maximum input and minimum sensitivity.

Typical power meter dynamic ranges:– +20 dBm to -70 dBm for Telephony– +30 dBm to -55 dBm for CATV– -20 dBm to -60 dBm for LAN


Optical Loss Budget

Maximum loss = Minimum power output of source minus minimum acceptable power level of receiver

Minimum loss = Maximum power output of source minus maximum acceptable power level of receiver

Optical Loss Budget:Bmax = Ptmin – Prmin

Bmin = Ptmax -Prmax

Opt

ical

Pow

er L

evel

(dB

m)

Maximum Loss (dB)

Minimum Loss (dB)

Ptmax

Prmax

Ptmin

Prmin


Optical Loss Budget (Example 1)

1000BASE-LX GBIC– Ptmax = -3 dBm

– Ptmin = -9.5 dBm

– Prmax = -3 dBm

– Prmin = -19 dBm

Questions:– Can you connect one GBIC to

another with only a patchcord?

– How can you ensure that the fiber system does not exceed the maximum loss?

Optical Loss Budget:Bmax = Ptmin – Prmin

Bmin = Ptmax -Prmax

Opt

ical

Pow

er L

evel

(dB

m)

Maximum Loss (dB) = 18.5 dB

Minimum Loss (dB) = 0 dB

Ptmax -3 dBm

Prmax -3 dBm

Ptmin -9.5 dBm

Prmin -19 dBm

fiber optic tests mark ortel sales support eng scte member and supporter

Documents