decusatis, c. (2002). handbook of fiber optic data communication (2nd ed.)

Contents Contributors Preface to the Second Edition Part 1 The Technology Chapter 1 Optical Fiber, Cable, and Connectors and Laser Technology Wenbin Jiang and Michael S.. Sundstrom a

DATA COMMUNI(ATI0N

HANDBOOK OF FIBER OPTIC

DATA COMMUNICATION

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02 03 04 05 RDC 9 8 7 6 5 4 3 2 1

To the people who give meaning to my life

and taught me to look for wonder in the world:

my wife, Carolyn, my daughters, Anne and Rebecca, my parents,

Contents

Contributors

Preface to the Second Edition

Part 1 The Technology

Chapter 1 Optical Fiber, Cable, and Connectors

and Laser Technology

Wenbin Jiang and Michael S Lebby

Chapter 3 Detectors for Fiber Optics

Carolyn J Sher DeCusatis and Ching-Long (John) Jiang

Chapter 4 Logic and Drive Circuitry

Ray D Sundstrom and Eric Maass

Function of the Optical Subassembly

Basic Properties of the Transmitter OSA

Basic Properties of the Receiver OSA

Coupling Radiation from a Laser Diode into a Fiber

Coupling Radiation from a Fiber into a Photodetector

Packaging of Optical Subassemblies

Optical Subassemblies for Parallel Optical Links

Outlook

References

Chapter 6 Fiber Optic Transceivers

Michael Langenwalter and Richard Johnson

Technical Description of Fiber Optic Transceivers

The Optical Interface

Noise Testing of Transceivers

Packaging of Transceivers (TRX)

Series Production of Transceivers

Transceivers Today and Tomorrow

Parallel Optical Links

References

Part 2 The Links

Casimer DeCusatis

7.1 Introduction

7.2 Link Budget Planning

7.3 Link Planning Considerations

Appendix A: Contact Information for Optoelectronics

and Fiber Optics Information

Contents

Appendix B: Some Accredited Homologation Test Labs

References

Chapter 8 Planning and Building the Optical Link

R T Hudson, D R King, T R Rhyne, and T A Torchia

Chapter 9 Testing Fiber Optic Local Area Networks (LANs)

Jim Hayes and Greg LeCheminant

Standardization of Testing Procedures

Fiber Optic Test Equipment Needed for Testing

Measuring Optical Power

Testing Loss

Testing Cable Loss

OTDR Testing

Troubleshooting Hints for the Cable Plant

Special Test Considerations for Gigabit Multimode Networks

Cable Plant Loss with Laser Sources

Bit Error Ratio Measurements

Characterizing Digital Communications Waveforms

Testing and Troubleshooting Networks

Transceiver Loopback Testing

Conclusion

Part 3 The Applications

Chapter 10 Introduction to Industry Standards

Schelto Van Doom

Chapter 11 Intramachine Communications

John D Crow and Alan E Benner

Current Intramachine Optics Applications

System Area Networks

S A N Physical Layer Technology Requirements

Copper vs Optical: Technology Trade-offs

Parallel Optical Interconnect Hardware

Examples of Parallel Optical Interconnect Links

Conclusions

References

and Synchronous Optical Network

Alan I;: Benner

How Fibre Channel Leverages Optical Data Communications

Web Resources and References

Daniel J Stigliani, JI:

ESCON System Overview

ESCON Link Design

Multimode Physical Layer

SingleMode Physical Layer

Planning and Installation of an ESCON Link

Loss Budget Analysis

Contents xi

Interface, Ethernet, and Token Ring

Part 4 The Manufacturing Technology

Light-Emitting Diode Fabrication

Wenbin Jiang and Michael S Lebby

Chapter 17 Receiver, Laser Driver, and Phase-Locked

Loop Design Issues

Chapter 19 Alignment Metrology and Techniques

Darrin P Clement, Ronald C Lasky, and Daniel Baldwin

Appendix A Measurement Conversion Tables

Appendix B Physical Constants

Appendix C Index of Professional Organizations

Appendix D OS1 Model

Appendix E Network Standards and Documents

Appendix F Data Network Rates

Appendix G Other Datacom Developments

Contributors

Numbers in parentheses indicate the pages on which the authors’ contributions begin

Daniel Baldwin (699), Manufacturing Research Center, School of Mechanical

Engineering, Georgia Institute of Technology, 8 13 Ferst Drive Northwest,

Atlanta, Georgia 30332

Carl Beckmann (435), Thayer School of Engineering, 8000 Cummings Hall,

Dartmouth College, Hanover, New Hampshire 03755

AlanF Benner (379,464), IBM Corporation, 2455 South Road, MS P967, Pough-

keepsie, New York 12601

Darrin P Clement (699), Maponics, 468 Garey Road, East Thetford, Vermont

05043

John D Crow (379), IBM Corporation, Thomas J Watson Research Center, York- Carolyn J Sher DeCusatis (89), formerly from Lighting Research Center, Rens- Casimer DeCusatis (217), IBM Corporation, 2455 South Road, MS P343, Pough- Jim Hayes (333) Fotec, Incorporated, 151 Mystic Avenue, Suite 7, Medford,

R T Hudson (292), Siecor Corporation, 800 17th Street Northwest, Hickory,

Ching-Long (John) Jiang (89), Amp Incorporated, Lytel Division, MS 300-001,

61 Chubb Way, Post Office Box 1300, Somerville, New Jersey 08876

Wenbin Jiang (41, 603), Phoenix Applied Research Center, Motorola, Incorpo-

rated, 2100 East Elliot Road, MS EL703, Tempe, Arizona 85284

town Heights, New York 10598

selaer Polytechnic Institute, Troy, New York 12180

keepsie, New York 12601

Massachusetts 02155

North Carolina 28601

xiii

Richard Johnson (1 59), Infineon Technologies North America Corporation, 1730

D R King (292), Siecor Corporation, 800 17th Street Northwest, Hickory, North Michael Langenwalter (159), Infineon Technologies AG, Fiber Optics Division, Ronald C Lasky (699), Consultant, 26 Howe Street, Medway, Massachusetts Michael S Lebby (41,603), Phoenix Applied Research Center, Motorola, Incor-

Greg LeCheminant (333), Hewlett-Packard, Santa Rosa Systems Division, Santa

Eric Maass (127), Motorola, Incorporated, 2 100 East Elliot Road, Tempe, Arizona Ulf L Osterberg (3), Thayer School of Engineering, Dartmouth College, Glenn Raskin (675), Motorola, Incorporated, 2501 South Price Road, M/D G651,

T R Rhyne (292), Siecor Corporation, 800 17th Street Northwest, Hickory, North Dave Siljenberg (655), IBM Corporation, 3605 Highway 52 North, Rochester, Herwig Stange (143), Infineon Technologies, Fiber Optics, 13623, Berlin, Ger- Daniel J Stigliani, Jr (506), IBM Corporation, 2455 South Road, Poughkeepsie,

Ray D Sundstrom (127), Motorola, Incorporated, 2501 South Price Road, M/D Rakesh Thapar (564), Marconi, Warrendale, Pennsylvania, 15086

T A Torchia (292), Siecor Corporation, 800 17th Street Northwest, Hickory, Schelto Van Doorn (367), Siemens Corporation, Santa Clara, California 95054

North First Street, San Jose, California 95112

Preface to the Second Edition

SONET’ on the Lambdas’

(by C DeCusatis, with sincere apologies to Milton3)

When Z consider how the light is bent Byjbers glassy in this Web World Wide, Tera- and Peta-, the bits Jly by Are they from Snell and Maxwell sent

Or through more base physics, which the Maker presents

(lambdas of God?) or might He come to chide

“Doth God require more bandwidth, light denied?”

Consultants may ask; but Engineers to prevent that murmul; soon reply “The Fortune e-500 do not need

mere light alone, nor its interconnect; who requests

this data, if not clients surjing the Web?” Their state

is processing, a billion MIPS or CPU cycles at giga-speed

Withoutfiber optic links that never rest, The servers also only stand and wait

When the first edition of this Handbook was published, the world of op- tical data communication appeared to be already well established, and its technology was a major driving force in the development of computers (both servers and clients), storage, and real-world applications in business, education, transportation, and many other sectors of the economy Even so,

we recognized at the time that the revolution in optical communications was only just beginning Today, at the dawn of a new millennium, there are tremendous opportunities for growth in this field, and we have seen the pace of new technology accelerate even further in recent years These many new developments, coupled with the success of the first edition, led

to the conclusion that the time was right to update and expand on this Handbook

Synchronous Optical Network

*The Greek symbol “lambda” or h is commonly used in reference to an optical wavelength 3The original author of the classic sonnet “On his blindness”

xv

The intervening period has seen many significant changes, which re- quired updating the original chapters; new types of lasers and photodetec- tors, a new physical layer interface for ESCON, new packaging technology for parallel optics, and many more revisions too numerous to mention have been included Many new chapters have also been added to address the rapidly accelerating rate of change which has characterized wavelength multiplexing, optically clustered servers, small form factor connectors and transceivers, special types of fiber optic cable, and other areas which would have been classified as emerging technologies only a short while ago Open standards, which to a great extent have created the Internet and the Web (re- member TCPAP?) also continue to evolve, and new standards are emerging

to deal with the requirements of the next-generation intelligent optical in- frastructure; some of these standards, such as MPLS and Infiniband, have been added to this edition There are also new chapters on the history

of communications technology (with apologies to those who have noted that it remains difficult to determine exactly who invented the first one of anything, and that the history of science is filled with tales of misplaced credit) There are also new predictions of the future, as envisioned by some

of the leading commercial technology forecasts Since the f i st edition, De- Cusatis’ Law has continued to hold; available data suggests that high-end network bandwidth will continue to grow at this pace for the foreseeable future Indeed, the proliferation of new optical interfaces has led the ed- itor to coin the Law of Cable Growth, also known as the First Corollary

to DeCusatis’ Law: the development of each new type of optical connec- tor interface will proliferate 2 orders of magnitude in new cable assembly types For example, if you happen to be a supplier of fiber optic cables, each new connector interface needs to be offered with 3 different fiber types (single mode, 50 micron multimode, and 62.5 micron multimode), 2

or 3 different cable jacket types (riser, LSZH, and plenum), 5 or 6 standard

lengths for common applications, and hybrid cables or adapter kits that are backward-compatible with all the previous types of optical connectors Thus, one new optical connector easily drives a hundred new cable assem- blies! We’ve attempted to create a guide to the increasing complexity of

optical cabling, and many other areas as well Jargon and buzzwords in the industry have also continued to grow; when the first edition was pub- lished, not too long ago, nobody h e w what a S A N or NAS was, let alone the difference between them Today, a resurgence of interest in Storage Area Networks and Network Attached Storage has made these and many other acronyms commonplace, but our readers have expressed their ongoing

Preface wii

frustration at repeatedly encountering AUA (another useless acronym) In

an effort to help, we've included a new glossary and table of acronyms in

this edition, as well as an expanded index

Today's business initiatives are inexorably linked to network bandwidth;

after all, your business can only grow as fast as information can be ex-

changed and acted upon Perhaps this is why leading analysts tell us worldwide bandwidth demand grew roughly 200% from 1998 to 2000, and will increase more than 400% before 2002 The statistics of bandwidth growth are truly astonishing It has been estimated that the entire Library of

Congress can be stored in about 17 TeraBytes of disk space; this is also the

current size of the package tracking database at United Parcel Services In July 2000, the communication platform at the Web search engine Yahoo! delivered 4.4 billion messages and averaged 680 million page views per

day In the Information Economy, the Fortune 1000 companies are expected

to add over 150 TeraBytes of storage capacity by 2003 Simply put, the demand for bandwidth exceeds the supply And this is just the beginning; even today, less than 25% of these companies have electronic transaction capabilities over the Web, and even less are enabled for true e-business applications And a recent University of California study, having estimated that the entire human race has accumulated about one exabyte (1018) of

information to date, goes on to predict that the second exabyte will be gener- ated within the next 3 years In this environment, we are beginning to see the

promise of all-optical networking emerge - application-neutral, distance- independent, infinitely scalable, user-centric networks that catalyze real- time global computing, advanced streaming multimedia, distance learning, telemedicine, and a host of other applications We hope that those who build and use these networks will benefit in some measure from this book

An undertaking such as this would not be possible without the concerted efforts of many contributing authors and a supportive staff at the publisher,

to all of whom I extend my deepest gratitude The following associate editors contributed to the first edition of the Handbook of Fiber Optic Data Communication: Eric Maass, Darrin Clement, and Ronald Lasky As always, this book is dedicated to my parents, who first helped me see the wonder in the world; to the memory of my godmother Isabel; and to my

would not have been possible

Dr Casimer DeCusatis, Editor Poughkeepsie, New York

Part 1 The Technology

Light is most accurately described as a vectorial electromagnetic wave Fortunately, this complex description of light is often not necessary for a satisfactory treatment of many important engineering applications

In the case of optical fibers used for tele- and data communication it is sufficient to use a scalar wave approximation to describe light propagation

in single-mode fibers and a ray approximation for light propagation in multimode fibers

For the ray approximation to be valid the diameter of the light beam has

to be much larger than the wavelength In the wave picture we will assume

a harmonically time-varying wave propagating in the z direction with phase constant B The electric field can be expressed as

This is more conveniently expressed in the phasor formalism as

where the real part of the right-hand side is assumed

3

HANDBOOK OF RBER OPTIC

DATA COMMUNICATION

Copyright Q 2002 by Academic Press

All rights of reproduction in any form reserved

A wave’s propagation in a medium is governed by the wave equation

For the particular wave in Eq (1.2) the wave equation for the electric z

[Transverse phase constant],

in the fiber, what their phase constants are, and their spatial transverse profile To do this we have to solve Eq (1.3) for a typical fiber geometry (Fig 1.1) Because of the inherent cylindrical geometry of an optical fiber,

Q (1.3) is transformed into cylindrical coordinates and the modes of spatial dependence are described with the coordinates r-, 4, and z Because the solution is dependent on the specific refractive index profile, it has to be specified In Fig 1.2 the most common refractive index profiles are shown For step-index profile in Fig 1.2c, a complete analytical set of solutions can

1 Optical Fiber, Cable, and Connectors 5

Fig 1.1 vpical fiber geometry Reprinted from Ref [l], p 12, courtesy of Academic

Press

be given [3] These solutions can be grouped into three different types of

modes: TE, TM, and hybrid modes, of which the hybrid modes are further

separated into EH and HE modes It turns out that for typical fibers used

in tele- and data communication the refractive index difference between

core and cladding, nl -n2, is so small (-0.002-0.008) that most of the TE,

TM, and hybrid modes are degenerate and it is sufficient to use a single

notation for all these modes-the LP notation An LP mode is referred

to as LPem, where the t and m subscripts are related to the number of

radial and azimuthal zeros of a particular mode The fundamental mode,

and the only one propagating in a single-mode fiber, is the LPol mode This

mode is shown in Fig 1.3, To quickly figure out if a particular LP mode will

propagate, it is very useful to define two dimensionless parameters, V and b

where a is the core radius, h is the wavelength of light, and A x y

The V number is sometimes called the normalized frequency

The normalized propagation constant b is defined as

(B2/k2) - nz n; - n2

where b is the phase constant of the particular LP mode, k is the propagation

constant in vacuum, and nl and n2 are the core and cladding refractive

indexes, respectively

Equation (1.5) is very cumbersome to use because b has to be calculated

from Eq (1.3) For LP modes Gloge et al [4] have shown that to a very good

accuracy the following formulas can be used to calculate b for different

L - I O p l l l

-h

Fig 1.2 Refractive index profiles of (a) step-index multimode fibers, (b) graded-index multimode fibers, (c) match-cladding single-mode fibers, (d, e) depressed-cladding, single- mode fibers, (f-h) dispersion-shifted fibers, and (i, j) dispersion-flattened fibers Reprinted from Ref [2], p 125, courtesy of Irwin

1 Optical Fiber, Cable, and Connectors 7

The graphs in Fig 1.4 were generated using Eqs (1.6) and (1.7) The

normalized propagation constant b can vary only between 0 and 1 for

guided modes; this corresponds to

n2k < B < n l k (1.8)

Therefore, for wavelengths longer than the cutoff wavelength the mode cannot propagate in the optical fiber

Cutoff values for the V number for a few LP modes are given in Table 1.1

The fundamental mode can, to better than 96% accuracy, be described using

a Gaussian function

(1.10)

where E , is the amplitude and 2wg is the mode field diameter (MFD)

(Fig 1.3) The meaning of the MFD is shown in Fig 1.5 The MFD for the fundamental mode is larger than the geometrical diameter in a

single-mode (SM) fiber and much smaller than the geometrical diameter

where a is the core radius Equation ( 1.1 1) is valid for wavelengths between

0.8 A,, and 2 A,,

1 Optical Fiber, Cable, and Connectors 9

Table 1.1 Cutoff Frequencies of Various LPp, Modes in a Step

J2Wd = Oi; Vc # 0

5.1356 8.4172 11.6198 14.7960

a Reprinted from Ref [5], p 380, courtesy of Cambridge University Press

Fig 1.5 The electric field of the HEll mode is transverse and approximately Gaussian The mode field diameter is determined by the points where the power is down by e-* or where the amplitude is down by e-l The MFD is not necessarily the same dimension as

the core Reprinted from Ref [ 6 ] , p 144, courtesy of Jrwin

If the radial distribution for higher order modes is needed, it is necessary

to use the Bessel functions [3] In Fig 1.6 the radial intensity distribution

is shown for five LP modes in a fiber with V = 8 Recommended specifi-

cations for a single-mode fiber are summarized in Table 1.2

1.1.3 MULTIMODE FIBER

The previous discussion has in principle been for a step-index MM fiber Because of the severe differences in propagation time between different modes in a step-index fiber, these are not commonly used in practice Instead, a graded refractive index core is used for a MM fiber (Fig 1.7)

1 Optical Fiber, Cable, and Connectors 11

Table 1.2 CCITT Recommendation G.652‘

Parameters

Cladding diameter

Mode field diameter

Cutoff wavelength A,,

a Reprinted from Ref 121 p 126 courtesy of h i n

Fig 1.7 The refractive index variation for a power law profile for different values of q

Reprinted from Ref [ 5 ] , p 396, courtesy of Cambridge University Press

The various graded-index profiles are generated by

for different q’s, q is called the profile exponent The optimum profile is the one that gives the minimum dispersion; this occurs for q at slightly less than 2

The total number of modes that can propagate in a MM fiber is given by

WKB approximation [ 3 ] Using this analysis the phase constants for the

different modes can be shown to obey the following relationship:

m d q + 2

p,,, = n k J l - 2A( ) , m = 1 , 2 , , N (1.14)

A first approach to estimate how much light can be coupled into an optical

fiber is to use the ray picture In this picture the light is confined within the core if it undergoes total internal reflection at the core-cladding boundary This will occur only for light entering the fiber within an acceptance cone defined by the angle 8 (Fig 1.8) Rather than stating the angle 8 for an optical fiber, it is the convention to give sin 8, which is called the numerical

aperture (NA) The NA is defined as

1 Optical Fiber, Cable, and Connectors 13

where n is the refractive index of the medium the light is coming from In the case of coupling into an optical fiber, light is usually coming from air

and subsequently n % 1 A more useful formula for the NA can be obtained

if we use the dimensionless parameter A,

For an incoherent light source such as a light emitting diode (LED) one

can show that the total power accepted by the fiber is given by [9]

P = B A ~ (NA)*, ~ ~ (1.17) where B is the LED’s radiance (units for radiance is watts per area and steradian)

It is more common to give a coupling efficiency; thus, giving the total power accepted by the fiber, the efficiency is defined as [ 101

(1.18)

where Pin is the power launched into the fiber and Pim the power accepted

by the LPem mode For link budget analyses it is more convenient to deal

with coupling losses in units of decibels a:

Coherent light from a laser can often be approximated with a Gaussian beam; furthermore, if we restrict ourselves to a SM fiber, so that the

LPol mode can also be approximated as a Gaussian field, it is possible

to calculate r ] analytically [7, 111:

(1.21)

Equation (1.21) takes into account four different coupling cases at once (Fig 1.9) If only one of these different coupling cases is present at a time

Eq (1.21) can be simplified to:

Case 1.1 Spot-size mismatch si + s2:

Case 1.2 Transverse offset A:

Case 1.3 Longitudinal offset AZ:

1 Optical Fiber, Cable, and Connectors 15

C

d Fig 1.9 Different coupling cases Reprinted from Ref [l], p 18, courtesy of Academic Press

Case 1.4 Angular misalignment 8:

If a lens is used in between the emitter and fiber, some modifications

to the previous formulas have to be done What the lens can do for us

is to match the output angle of the emitter to the acceptance angle of the receiving fiber If properly done, the power coupled into the fiber is multiplied with the lens magnification factor M : M = 2, (see Fig 1.10) All the preceding formulas need to be corrected for reflection losses If the

Table 1.3 Scattering Loss for Several Representative Glass Materials"

refractive index of the medium between the source and the fiber is denoted

no, the coupled power into the fiber is reduced with a factor R,

(1.26)

1.2 Optical Fiber Characterization

The material is primarily chosen to provide the minimum attenuation Table 1.3 shows order of magnitude attenuation at three different wave- lengths for four common glass types

For tele- and data communication fibers, fused silica glass is the pre- ferred material To provide guiding of the light, the core of the fiber is doped with a few molar percentage of a substance that increases the refrac- tive index It is also possible to dope the cladding such that its refractive index becomes lower than the pure silica glass index in the core (Fig 1.1 1)

1 Optical Fiber, Cable, and Connectors 17

Table 1.4 Factors Affecting Attenuation'

Intrinsic loss mechanisms

Tail of infrared absorption by S i 4 coupling

Tail of ultraviolet absorption due to electron transitions in defects Rayleigh scattering due to spatial fluctuations of the refractive index

Absorption by molecular vibration of OH

Absorption by transition metals

Geometrical nonuniformity at core-cladding boundary

Imperfection at connection or splicing between fibers

Attenuation is a very important factor in designing effective long-distance

fiber optic networks Consequently, the fabrication methods have improved dramatically during the past 30 years so that attenuation is measured in a few tenths of a d B h The dB is defined in Eq (1.19) The various factors affecting the attenuation, in the 0.8- to 1.6-pm wavelength region, are listed

in Table 1.4 Figure 1.12 shows schematically how some of the factors

the three different transmission windows at 800,1300, and 1550 nm, are a 2

or 3, (0.5, and 50.2 dB/km, respectively These numbers are for SM fibers; from Fig 1.13 it can be seen that MM fibers have slightly higher losses The losses dealt with to date have been due to either intrinsic properties of the glass or extrinsic properties (such as OH and transition metal contents) that come from the particular fabrication method used In addition, there are bending losses If the fiber has been improperly cabled or installed these

1 Optical Fiber, Cable, and Connectors 19

Fig 1.13 Wavelength dependence of fiber attenuation Reprinted from Ref [14], p 8

Copyright 0 1989 by Hewlett Packad Company Reproduced with permission

5 -

800 900 1000 1100 1200 1300 1400 1500 1600

h, nm Fig 1.14 Bend-inducedlosses ofopticalfibers ReprintedfromRef [15],p 1.33.courtesy

of McGraw-Hill

bending losses can be substantial Bending losses are divided into micro- and macro-bending losses Micro-bending losses are due to nanometer- size deviations in the fiber Macro-bending losses are due to visible bends

in the fiber Figure 1.14 shows qualitatively how micro- and macrobends contribute to the overall loss in a SM and MM fiber