Optical Fiber Telecommunications Volume VIB: Systems and Networks

By Ivan Kaminow, Tingye Li and Alan E Willner

Optical Fiber Telecommunications VI (A&B) is the sixth in a series that has chronicled the progress in the R&D of lightwave communications since the early 1970s. Written by active authorities from academia and industry, this edition brings a fresh look to many essential topics, including devices, subsystems, systems and networks. A central theme is the enabling of high-bandwidth communications in a cost-effective manner for the development of customer applications. These volumes are an ideal reference for R&D engineers and managers, optical systems implementers, university researchers and students, network operators, and investors.

Volume A is devoted to components and subsystems, including photonic integrated circuits, multicore and few-mode fibers, photonic crystals, silicon photonics, signal processing, and optical interconnections.

Volume B is devoted to systems and networks, including advanced modulation formats, coherent detection, Tb/s channels, space-division multiplexing, reconfigurable networks, broadband access, undersea cable, satellite communications, and microwave photonics.

• All the latest technologies and techniques for developing future components and systems
• Edited by two winners of the highly prestigious OSA/IEEE John Tyndal award and a President of IEEE's Lasers & Electro-Optics Society (7,000 members)
• Written by leading experts in the field, it is the most authoritative and comprehensive reference on optical engineering on the market

• Language: English
• Publisher: Academic Press
• Release date: May 11, 2013
• ISBN: 9780123972378

Book preview

Optical Fiber Telecommunications VIB

Systems and Networks

Sixth Edition

Ivan P. Kaminow

Tingye Li

Alan E. Willner

Table of Contents

Cover image

Title page

Dedication

Copyright

Dedication 2

Preface—Overview of OFT VI A & B

Six Editions

OFT VI Volume A: Components and Subsystems

OFT VI Volume B: Systems and Networks

Chapter 1. Fiber Nonlinearity and Capacity: Single-Mode and Multimode Fibers

1.1 Introduction

1.2 Network Traffic and Optical Systems Capacity

1.3 Information Theory

1.4 Single-Mode Fibers: Single Polarization

1.5 Single-Mode Fibers: Polarization-Division Multiplexing

1.6 Multicore and Multimode Fibers

1.7 Conclusion

References

Chapter 2. Commercial 100-Gbit/s Coherent Transmission Systems

2.1 Introduction

2.2 Optical Channel Designs

2.3 100G Channel—From Wish to Reality

2.4 Introduction of 100G Channels to Service Provider Networks

2.5 Impact of Commercial 100G System to Transport Network

2.6 Outlook Beyond Commercial 100G Systems

2.7 Summary

References

Chapter 3. Advances in Tb/s Superchannels

3.1 Introduction

3.2 Superchannel Principle

3.3 Modulation

3.4 Multiplexing

3.5 Detection

3.6 Superchannel Transmission

3.7 Networking Implications

3.8 Conclusion

References

Chapter 4. Optical Satellite Communications

4.1 Introduction

4.2 Lasercom Link Budgets

4.3 Laser Beam Propagation Through the Atmosphere

4.4 Optical Transceivers for Space Applications

4.5 Space Terminal

4.6 Ground Terminal

4.7 List of Acronyms

References

Chapter 5. Digital Signal Processing (DSP) and Its Application in Optical Communication Systems

5.1 Introduction

5.2 Digital Signal Processing and Its Functional Blocks

5.3 Application of DBP-Based DSP to Optical Fiber Transmission in the nonlinear regime

5.4 Summary and Future Questions

References

Chapter 6. Advanced Coding for Optical Communications

6.1 Introduction

6.2 Linear Block Codes

6.3 Codes on Graphs

6.4 Coded Modulation

6.5 Adaptive Nonbinary LDPC-Coded Modulation

6.6 LDPC-Coded Turbo Equalization

6.7 Information Capacity of Fiber-Optics Communication Systems

6.8 Concluding Remarks

References

Chapter 7. Extremely Higher-Order Modulation Formats

7.1 Introduction

7.2 Spectral Efficiency of QAM Signal and Shannon Limit

7.3 Fundamental configuration and key components of QAM coherent optical transmission

7.4 Higher-Order QAM Transmission Experiments

7.5 Conclusion

References

Chapter 8. Multicarrier Optical Transmission

8.1 Historical perspective of optical multicarrier transmission

8.2 OFDM Basics

8.3 Optical Multicarrier Systems Based on Electronic FFT

8.4 Optical Multicarrier Systems Based on Optical Multiplexing

8.5 Nonlinearity in Optical Multicarrier Transmission

8.6 Applications of Optical Multicarrier Transmissions

8.7 Future Research Directions for Multicarrier Transmission

References

Chapter 9. Optical OFDM and Nyquist Multiplexing

9.1 Introduction

9.2 Orthogonal Shaping of Temporal or Spectral Functions for Efficient Multiplexing

9.3 Optical Fourier Transform Based Multiplexing

9.4 Encoding and Decoding of OFDM Signals

9.5 Conclusion

9.6 Mathematical Definitions and Relations

References

Chapter 10. Spatial Multiplexing Using Multiple-Input Multiple-Output Signal Processing

10.1 Optical Network Capacity Scaling Through Spatial Multiplexing

10.2 Coherent MIMO-SDM with Selective Mode Excitation

10.3 MIMO DSP

10.4 Mode Multiplexing Components

10.5 Optical Amplifiers for Coupled-Mode Transmission

10.6 Systems Experiments

10.7 Conclusion

References

Chapter 11. Mode Coupling and its Impact on Spatially Multiplexed Systems

11.1 Introduction

11.2 Modes and Mode Coupling in Optical Fibers

11.3 Modal Dispersion

11.4 Mode-Dependent Loss and Gain

11.5 Direct-Detection Mode-Division Multiplexing

11.6 Coherent Mode-Division Multiplexing

11.7 Conclusion

References

Chapter 12. Multimode Communications Using Orbital Angular Momentum

12.1 Perspective on Orbital Angular Momentum (OAM) Multiplexing in Communication Systems

12.2 Fundamentals of OAM

12.3 Techniques for OAM Generation, Multiplexing/Demultiplexing, and Detection

12.4 Free-Space Communication Links Using OAM Multiplexing

12.5 Fiber-Based Transmission Links

12.6 Optical Signal Processing Using OAM

12.7 Future Challenges of OAM Communications

References

Chapter 13. Transmission Systems Using Multicore Fibers

13.1 Expectations of Multicore Fibers

13.2 MCF Design

13.3 Methods of Coupling to MCFs

13.4 Transmission Experiments with Uncoupled Cores

13.5 Laguerre-Gaussian Mode Division Multiplexing Transmission in MCFs

References

Chapter 14. Elastic Optical Networking

14.1 Introduction

14.2 Enabling Technologies

14.3 The EON Vision and Some New Concepts

14.4 A Comparison of EON and Fixed DWDM

14.5 Standards Progress

14.6 Summary

References

Chapter 15. ROADM-Node Architectures for Reconfigurable Photonic Networks

Summary

15.1 Introduction

15.2 The ROADM Node

15.3 Network Applications: Studies and Demonstrations

15.4 Two Compatible Visions of the Future

15.5 Conclusions

References

Chapter 16. Convergence of IP and Optical Networking

16.1 Introduction

16.2 Motivation

16.3 Background

16.4 Standards

16.5 Next-Generation Control and Management

References

Chapter 17. Energy-Efficient Telecommunications

17.1 Introduction

17.2 Energy Use in Commercial Optical Communication Systems

17.3 Energy in Optical Communication Systems

17.4 Transmission and Switching Energy Models

17.5 Network Energy Models

17.6 Conclusion

References

Chapter 18. Advancements in Metro Regional and Core Transport Network Architectures for the Next-Generation Internet

18.1 Introduction

18.2 Network Architecture Evolution

18.3 Transport Technology Innovations

18.4 The Network Value of Photonics Technology Innovation

18.5 The Network Value of Optical Transport Innovation

18.6 Outlook

18.7 Summary

References

Chapter 19. Novel Architectures for Streaming/Routing in Optical Networks

19.1 Introduction and Historical Perspectives on Connection and Connectionless Oriented Optical Transports

19.2 Essence of the Major Types of Optical Transports: Optical Packet Switching (OPS), Optical Burst Switching (OBS), and Optical Flow Switching (OFS)

19.3 Network Architecture Description and Layering

19.4 Definition of Network Capacity and Evaluation of Achievable Network Capacity Regions of Different Types of Optical Transports

19.5 Physical Topology of Fiber Plant and Optical Switching Functions at Nodes and the Effects of Transmission Impairments and Session Dynamics on Network Architecture

19.6 Network Management and Control Functions and Scalable Architectures

19.7 Media Access Control (MAC) Protocol and Implications on Routing Protocol Efficiency and Scalability

19.8 Transport Layer Protocol for New Optical Transports

19.9 Cost, Power Consumption Throughput, and Delay Performance

19.10 Summary

References

Chapter 20. Recent Advances in High-Frequency (>10GHz) Microwave Photonic Links

20.1 Introduction

20.2 Photonic Links for Receive-Only Applications

20.3 Photonic Links for Transmit and Receive Applications

References

Chapter 21. Advances in 1-100GHz Microwave Photonics: All-Band Optical Wireless Access Networks Using Radio Over Fiber Technologies

21.1 Introduction

21.2 Optical RF Wave Generation

21.3 Converged ROF Transmission System

21.4 Conclusions

References

Chapter 22. PONs: State of the Art and Standardized

22.1 Introduction to PON

22.2 TDM PONs: Basic Design and Issues

22.3 Video Overlay

22.4 WDM PONs: Common Elements

22.5 FDM-PONs: Motivation

22.6 Hybrid TWDM-PON

22.7 Summary and Outlook

References

Chapter 23. Wavelength-Division-Multiplexed Passive Optical Networks (WDM PONs)

23.1 Introduction

23.2 Light Sources for WDM PON

23.3 WDM PON Architectures

23.4 Long-Reach WDM PONs

23.5 Next-Generation High-Speed WDM PON

23.6 Fault Monitoring, Localization and Protection Techniques

23.7 Summary

Appendix: Acronyms

References

Chapter 24. FTTX Worldwide Deployment

24.1 Introduction

24.2 Background of Fiber Architectures

24.3 Technology Variants

24.4 Status and FTTX Deployments Around the World

24.5 What’s Next?

24.6 Summary

References

Chapter 25. Modern Undersea Transmission Technology

25.1 Introduction

25.2 Coherent Transmission Technology in Undersea Systems

25.3 Increasing Spectral Efficiency by Bandwidth Constraint

25.4 Nyquist Carrier Spacing

25.5 Increasing Spectral Efficiency by Increasing the Constellation Size

25.6 Future Trends

25.7 Summary

List of Acronyms

References

Index

Dedication

To the memory of Dr. Tingye Li

(July 7, 1931 – December 27, 2012)

A pioneer, luminary, friend, mentor, and champion of our field.

We will miss him dearly.

From the optical communications community

Copyright

Academic Press is an imprint of Elsevier

The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK

225 Wyman Street, Waltham, MA 02451, USA

Sixth edition 2013

Copyright © 2013 Elsevier Inc. All rights reserved.

Permissions throughout the work have been obtained directly from the publishers, including primarily IEEE, Nature, OSA and SPIE, among others.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher.

Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: [e-mail]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material.

Notice

No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made.

Library of Congress Cataloging-in-Publication Data

A catalog record for this book is availabe from the Library of Congress

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN: 978-0-12-396960-6

For information on all Academic Press publications visit our web site at books.elsevier.com

Printed and bound in the US

13 14 15 16 17 10 9 8 7 6 5 4 3 2 1

Dedication 2

For Florence, Paula, Leonard, and Ellen with love – IPK

For Edith, Debbie, and Kathy with love – TL

For Michelle, Moshe, Asher, Ari and Yaakov with love – AEW

Preface—Overview of OFT VI A & B

Optical Fiber Telecommunications VI (OFT VI) is the sixth installment of the OFT series. Now 34 years old, the series is a compilation by the research and development community of progress in the field of optical fiber communications. Each edition reflects the current state of the art at the time. As editors, we started with a clean slate and selected chapters and authors to elucidate topics that have evolved since OFT V or that have now emerged as promising areas of research and development.

Six Editions

Installments of the series have been published roughly every 5–8 years and chronicle the natural evolution of the field:

• In the late 1970s, the original OFT (Chenoweth and Miller, 1979) was concerned with enabling a simple optical link, in which reliable fibers, connectors, lasers, and detectors played the major roles.

• In the late 1980s, OFT II (Miller and Kaminow, 1988) was published after the first field trials and deployments of simple optical links. By this time, the advantages of multi-user optical networking had captured the imagination of the community and were highlighted in the book.

• OFT III (Kaminow and Koch, 1997) explored the explosion in transmission capacity in the early-to-mid-1990s, made possible by the erbium-doped fiber amplifier (EDFA), wavelength-division-multiplexing (WDM), and dispersion management.

• By 2002, OFT IV (Kaminow and Li, 2002) dealt with extending the distance and capacity envelope of transmission systems. Subtitle nonlinear and dispersive effects, requiring mitigation or compensation in the optical and electrical domains, were explored.

• OFT V (Kaminow, Li, and Willner, 2008) moved the series into the realm of network management and services, as well as employing optical communications for ever-shorter distances. Using the high-bandwidth capacity in a cost-effective manner for customer applications started to take center stage.

• The present edition, OFT VI (Kaminow, Li, and Willner, 2013), continues the trend of photonic integrated circuits, higher-capacity transmission systems, and flexible network architectures. Topics that have gained much interest in increasing performance include coherent technologies, higher-order modulation formats, and space-division-multiplexing. In addition, many of the topics from earlier volumes are brought up to date and new areas of research which show promise of impact are featured.

Although each edition has added new topics, it is also true that new challenges emerge as they relate to older topics. Typically, certain devices may have adequately solved transmission problems for the systems of that era. However, as systems become more complex, critical device technologies that might have been considered a solved problem would now have new requirements placed upon them and need a fresh technical treatment. For this reason, each edition has grown in sheer size, i.e. adding the new and, if necessary, re-examining the old.

An example of this circular feedback mechanism relates to the fiber itself. At first, systems simply required low-loss fiber. However, long-distance transmission enabled by EDFAs drove research on low-dispersion fiber. Further, advances in WDM and the problems of nonlinear effects necessitated development of non-zero-dispersion fiber. Cost and performance considerations today drive research in plastic fibers, highly bendable fibers, few-mode fibers, and multicore fibers. We believe that these cycles will continue.

Perspective of the past 5 years

OFT V was published in 2008. At that point, our field was still emerging from the unprecedented upheaval circa 2000, at which time worldwide telecom traffic ceased being dominated by the slow-growing voice traffic and was overtaken by the rapidly growing Internet traffic. The irrational investment exuberance and subsequent depression-like period of oversupply (i.e. the bubble-and-bust) wreaked havoc on our field. We are happy to say that, by nearly all accounts, the field continues to gain strength again and appears to have entered a stage of rational growth. Demand for bandwidth continues to grow at a very healthy rate. Capacity needs are real, and are expected to continue in the future.

We note that optical fiber communications is firmly entrenched as part of the global information infrastructure. For example: (i) there would be no Internet as we know it if not for optics, (ii) modern data centers may have as many as 1,000,000 lasers to help interconnect boards and machines, and (iii) Smartphones would not be so smart without the optical fiber backbone.

A remaining question is how deeply will optical fiber penetrate and complement other forms of communications, e.g. wireless, access and on-premises networks, Interconnections, satellites, etc. The odds are that, indeed, optics will continue to play a significant role in assisting all types of future communications. This is in stark contrast to the voice-based future seen by OFT, published in 1979, which occurred before the first commercial intercontinental or transatlantic cable systems deployed in the 1980s. We now have Tbit/s systems for metro and long-haul networks. It is interesting and exciting to contemplate what topics, concerns, and innovations might be contained in the next edition of the series, OFT VII.

In this edition, OFT VI, we have tried to capture the rich and varied technical advances that have occurred in our field. Innovations continue to abound! We hope our readers learn and enjoy from all the chapters.

We wish sincerely to thank Tim Pitts, Charlie Kent, Susan Li, Jason Mitchell of Elsevier and Hao Huang of USC for their gracious and invaluable support throughout the publishing process. We are also deeply grateful to all the authors for their laudable efforts in submitting their scholarly works of distinction. Finally, we wish to thank the many people whose insightful suggestions were of great assistance.

Below are brief highlights of the different chapters in the two volumes.

OFT VI Volume A: Components and Subsystems

1A Advances in Fiber Distributed-Feedback Lasers

Michalis N. Zervas

This chapter covers advances in fiber distributed-feedback (DFB) lasers and their potential use in modern coherent optical telecommunication systems. In particular, it describes novel DFB cavity designs and configurations and considers their impact on the laser performance. Special emphasis is given to the fiber parameters that define the power scalability and stability, the polarization performance, as well as the linewidth and phase-noise characteristics. The wavelength coverage and tunability mechanisms are also discussed. The chapter finally reviews the use of fiber DFB lasers in non-telecom applications, such as advanced optical fiber sensors, and concludes with an outlook of the fiber laser technologies and their future prospects.

2A Semiconductor Photonic Integrated Circuit Transmitters and Receivers

Radhakrishnan Nagarajan, Christopher Doerr, and Fred Kish

This chapter covers the field of semiconductor photonic integrated circuits (PIC) used in access, metro, long-haul, and undersea telecommunication networks. Although there are many variants to implementing optical integration, the focus is on monolithic integration where multiple semiconductor devices, up to many hundreds in some cases, are integrated onto the same substrate. Monolithic integration poses the greatest technical challenge and the biggest opportunity for bandwidth and size scaling. The PICs discussed here are based on the two most popular semiconductor material systems: Groups III–V indium phosphide-based devices and Group IV silicon-based devices. The chapter also covers the historical evolution of the technology from the decades-old original proposal to the current-day Tbit/s class, coherent PICs.

3A Advances in Photodetectors and Optical Receivers

Andreas Beling and Joe C. Campbell

This chapter reviews the significant advances in photodetectors that have occurred since Optical Fiber Telecommunications V. The quests for higher-speed p-i-n detectors and lower-noise avalanche photodiodes (APDs) with high gain-bandwidth product remain.

To a great extent, high-speed structures have coalesced to evanescently coupled waveguide devices; bandwidths exceeding 140 GHz have been reported. A primary APD breakthrough has been the development of Ge on Si separate-absorption-and-multiplication devices that achieve long-wavelength response with the low-noise behavior of Si. For III–V compound APDs, ultra-low noise has been achieved by strategic use of complex multilayer multiplication regions that provide a more deterministic impact ionization. However, much of the excitement and innovation have focused on photodiodes that can be incorporated into InP-based integrated circuits and photodetectors for Si photonics.

4A Fundamentals of Photonic Crystals for Telecom Applications— Photonic Crystal Lasers

Susumu Noda

Photonic crystals, in which the refractive index changes periodically, provide an exciting tool for the manipulation of photons and have made substantial progresses in recent years. This chapter first introduces research activities that are geared toward realizing the ultimate nanolaser using the photonic bandgap effect. Important aspects of this effort are in the achievement of spontaneous emission suppression and strong optical confinement using a photonic nanocavity. During the process of implementation of this goal, interesting phenomena, which can be classified as Quantum Anti-Zeno effect, have been observed. The rest of the chapter focuses on the current state of research in the field of broad-area coherent photonic crystal lasers using the band-edge effect, which occupies a position opposite to that of nanolasers discussed above. The main characteristics of these lasers will be discussed, including their high-power operation, the generation of tailored beam patterns, the surface-emitting laser operation in the blue-violet region, and even the beam-steering functionality.

5A High-Speed Polymer Optical Modulators

Raluca Dinu, Eric Miller, Guomin Yu, Baoquan Chen, Annabelle Scarpaci, Hui Chen, and Corey Pilgrim

Recent advances in thin-film-polymer-on-silicon (TFPS) technology have provided the foundation to support commercial devices manufactured at production levels. A fundamental understanding of the material systems and fabrication techniques has been demonstrated, and will provide a stable platform for future developments to support next-generation applications. The chapter focuses on high-speed polymer-based optical modulators and on the molecular engineering of chromophores. The design of electron donor, bridge, electron acceptor, and isolating groups are discussed. Finally, the current commercial technologies are presented.

6A Nanophotonics for Low-Power Switches

Lars Thylen, Petter Holmström, Lech Wosinski, Bozena Jaskorzynska, Makoto Naruse, Tadashi Kawazoe, Motoichi Ohtsu, Min Yan, Marco Fiorentino, and Urban Westergren

Switches and modulators are key devices in ubiquitous applications of photonics: telecom, measurement equipment, sensor, and the emerging field of optical interconnects in high-performance computing systems. The latter could accomplish a breakthrough in offering a mass market for these switches. This chapter deals with photonic switches and the quest for the partly interlinked properties of low-power dissipation in operation and nanostructured photonics. It first summarizes some of the most important existing and emerging materials for nanophotonics lowpower switches, and describes their physical mechanisms, operation mode, and characteristics. The chapter then focuses on basic operation and power dissipation issues of electronically controlled switches, which in many important cases by using a simple model are operated by charging and discharging capacitors and thus changing absorption and/or refraction properties of the medium between the capacitor plates. All optical switches are also discussed and some present devices are presented.

7A Fibers for Short-Distance Applications

John Abbott, Scott Bickham, Paulo Dainese, and Ming-Jun Li

This chapter first reviews the current use of multimode fibers (MMF) with short-wavelength VCSELs for short-distance applications. Standards are in place for 100 Gbit/s applications based on 10 Gbit/s optics and are being developed for ∼25 Gbit/s optics. Then it briefly introduces the theory of light propagation in multimode fibers. The actual performance of an MMF link (the bit error rate and inter-symbol interference) depends on both the fiber and the laser. Effective model bandwidth, which includes both fiber and laser effects, will be discussed, and the method of characterizing fiber with the differential-mode-delay measurement and the laser with the encircled flux measurement will be summarized as well. Bend-insensitive multimode fiber is then presented, explaining how the new fiber achieves high bandwidth with low bend loss. New fibers for short-distance consumer applications and home networking are discussed. Finally, fibers designed for high-performance computing are reviewed, including multicore fibers for optical interconnects.

8A Few-Mode Fiber Technology for Spatial Multiplexing

David W. Peckham, Yi Sun, Alan McCurdy, and Robert Lingle Jr.

This chapter gives an overview of design and optimization of few-mode optical fibers (FMF) for space-division-multiplexed transmission. The design criteria are outlined, along with performance limitations of the traditional step-profile and graded-index profiles. The trade-offs between number of usable optical modes (related to total channel capacity), differential group delay, differential mode attenuation, mode coupling, and the impact on multiple-input and multiple-output (MIMO) receiver complexity are outlined. Improved fiber designs are analyzed which maximize channel capacity with foreseeable next-generation receiver technology. FMF measurement technology is overviewed.

9A Multi-Core Optical Fibers

Tetsuya Hayashi

Spatial division multiplexing attracts lots of attention for tackling the capacity crunch, which is anticipated as a problem in the near future, and therefore various types of optical fibers and multiplexing methods have been intensively researched in recent years. This chapter introduces the multi-core fibers for spatial division multiplexed transmission. It describes various characteristics specific to the multi-core fibers, which have been elucidated theoretically and experimentally in recent years. Though there are many important factors, many pages are devoted especially to the description of inter-core crosstalk, which is crucial when signals are transmitted over each core independently. The chapter also describes other characteristics related to the improvement of core density.

10A Plastic Optical Fibers and Gb/s Data Links

Yasuhiro Koike and Roberto Gaudino

As high-speed data processing and communication systems are required, plastic optical fibers (POFs) become promising candidates for optical interconnects as well as optical networking in local area networks. This chapter presents an overview of the evolution of POF, reviewing the technical achievements of both fiber design and system architectures that today allow using POF for Gb/s data links. In particular, the chapter presents the different POF materials such as polymethyl methacrylate (PMMA), perfluorinated polymers, types such as step-index POF and graded-index POF, as well as the POF production process, describing the resulting optical characteristics in terms of attenuation, dispersion, and bandwidth. The main applications of POF in industrial automation, home networking, and local area networks are also discussed.

11A Integrated and Hybrid Photonics for High-Performance Interconnects

Nikos Bamiedakis, Kevin A. Williams, Richard V. Penty, and Ian H. White

Optical interconnection technologies are increasingly deployed in high-performance electronic systems to address challenges in connectivity, size, bandwidth, latency, and cost. Projected performance requirements lead to formidable cost and energy efficiency challenges. Hybrid and integrated photonic technologies are currently being developed to reduce assembly complexity and to reduce the number of individually packaged parts. This chapter provides an overview of the important challenges that photonics currently face, identifies the various optical technologies that are being considered for use at the different interconnection levels, and presents examples of demonstrated state-of-the-art optical interconnection systems. Finally, the prospects and potential of these technologies in the near future are discussed.

12A CMOS Photonics for High-Performance Interconnects

Jason Orcutt, Rajeev Ram, and Vladimir Stojanović

For many applications, multicore chips are primarily constrained by the latency, bandwidth, and capacity of the external memory system. One of the most significant challenges is how to effectively connect on-chip processors to off-chip memories. This chapter introduces optical interconnects as a possible solution to the emerging performance wall in high-density supercomputer applications, arising from limited bandwidth and density of on-chip interconnects and chip-to-chip (processor-to-memory) electrical interfaces. The chapter focuses on the translation of system- and link-level performance metrics to photonic component requirements. The topics to be developed include network topology, photonic link components, circuit and system design for photonic links.

13A Hybrid Silicon Lasers

Brian R. Koch, Sudharsanan Srinivasan, and John E. Bowers

The term hybrid silicon laser refers to a laser that has a silicon waveguide and a III–V material that is in close optical contact. In this structure, the optical confinement can be easily transferred from one material to the other and intermediate modes exist for which the light is contained in both materials simultaneously. In hybrid silicon lasers, the optical gain is provided by the electrically pumped III–V material and the optical cavity is ultimately formed by the silicon waveguide. This type of laser can be heterogeneously integrated with silicon components that have superior performance compared to III–V components. These lasers can be fabricated in high volumes as components of complex photonic integrated circuits, largely with CMOS-compatible processes. These traits are expected to allow for highly complex, non-traditional photonic integrated circuits with very high yields and relatively low manufacturing costs. This chapter discusses the theory of hybrid silicon lasers, wafer-bonding techniques, examples of experimental results, examples of system demonstrations based on hybrid silicon lasers, and prospects for future devices.

14A VCSEL-Based Data Links

Julie Sheridan Eng and Chris Kocot

Vertical cavity surface emitting laser (VCSEL)-based data links are attractive due to their low-power dissipation and low-cost manufacturability. This chapter reviews the foundations for this technology, as well as the device and module design challenges of extending the data rate beyond the current level. The chapter begins with a review of data communications from the business perspective, and continues with a brief discussion of the current and future standards. This is followed by a survey of recent advances in VCSELs, including data links operating at 28 Gbit/s. Recent efforts on ultra-fast data links are reviewed and the advantages of the different approaches are discussed. The chapter also examines key design aspects of optical transceiver modules and focuses on novel applications in high-performance computing using both multi-mode and single-mode fiber optics. The importance of the device/component-level and system-level modeling is highlighted, and some modeling examples are shown with comparison to measured data. The chapter concludes with a comparison of the VCSEL-based data links with other competing technologies, including silicon photonics and short-cavity edge-emitting lasers.

15A Implementation Aspects of Coherent Transmit and Receive Functions in Application-Specific Integrated Circuits

Andreas Leven and Laurent Schmalen

One of the most challenging components of an optical coherent communication system is the integrated circuits (ICs) that process the received signals or condition the transmit signals. This chapter discusses implementation aspects of these ICs and their main building blocks, as data converters, baseband signal processing, forward error correction, and interfacing. This chapter also highlights selected implementation details for some baseband signal processing blocks of a coherent receiver. The latest generation of coherent ICs also supports advanced forward error correction techniques based on soft decisions. The circuits for encoding and decoding low-density parity check (LDPC) codes are introduced and evaluation of different forward error correction schemes based on a set of recorded measurement data is presented in this chapter.

16A All-Optical Regeneration of Phase-Encoded Signals

Joseph Kakande, Radan Slavík, Francesca Parmigiani, Periklis Petropoulos, and David Richardson

This chapter reviews the general principles and approaches used to regenerate phase-encoded signals of differing levels of coding complexity. It first reviews different approaches and nonlinear processes that may be used to perform the regeneration of phase-encoded signals. The primary focus is on parametric effects, which as explained previously can operate directly on the optical phase. The chapter then proceeds to review progress on regenerating the simplest of phase modulation formats, namely DPSK/BPSK- and for which the greatest progress has been made to date. In the following, the progress in regenerating more complex modulation format signals—in particular (D)QPSK and other M-PSK signals—is discussed. The chapter also reviews the choice of nonlinear components available to construct phase regenerators. Finally, it reviews the prospects for regenerating even more complex signals including QAM and mixed phase-amplitude coding variants.

17A Ultra-High-Speed Optical Time Division Multiplexing

Leif Katsuo Oxenløwe, Anders Clausen, Michael Galili, Hans Christian Hansen Mulvad, Hua Ji, Hao Hu, and Evarist Palushani

The attraction of optical time division multiplexing (OTDM) technology is the promise of achieving higher bit rates per channel than electronics could provide, thus alleviating the so-called electronic speed bottleneck. In this chapter, the state-of-the-art OTDM systems are presented, with a focus on experimental demonstrations. This chapter especially highlights demonstrations at 640–1280 Gbaud per polarization based on a variety of materials and functionalities. Many essential network functionalities are available today using a plethora of available materials, so now it is time to look at new network scenarios that take advantage of the serial nature of the data, e.g. try to come up with practical schemes for ultra-high bit rate optical data packets in supercomputers or within data centers.

18A Technology and Applications of Liquid Crystal on Silicon (LCoS) in Telecommunications

Stephen Frisken, Ian Clarke, and Simon Poole

Liquid crystal is now the dominant technology for flat-screen displays and has been used in telecom systems since the late 1990s. More recently, the adoption of liquid crystals in Wavelength Selective Switches—with the control of light on a pixel-by-pixel basis—has been enabled by developments in Liquid Crystal on Silicon (LCoS) backplane technologies derived from projection displays. This chapter presents the principles of operation of liquid crystals, focusing in particular on how they operate within an LCoS chip. It then explains in detail the design and operation of an LCoS-based wavelength selective switch (WSS), with particular emphasis on the key optical parameters that determine performance in an optical communications network. In the final section, the chapter briefly describes the broad scope of new opportunities that arise from the intrinsic performance and flexibility of LCoS as a switching medium.

OFT VI Volume B: Systems and Networks

1B Fiber Nonlinearity and Capacity: Single-Mode and Multimode Fibers

René-Jean Essiambre, Robert W. Tkach, and Roland Ryf

This chapter presents the trends in optical network traffic and commercial system capacity, discusses fundamentals of nonlinear capacity of single-mode fibers, and indicates that improvements in the properties of single-mode fibers only moderately increase the nonlinear fiber capacity. This leads to the conclusion that fiber capacity can be most effectively grown by increasing the number of spatial modes. This chapter also discusses nonlinear propagation in multimode fiber, a complex field still largely unexplored. It gives a basic nonlinear propagation equation derived from the Max-well equation, along with simplified propagation equations in the weak- and strong-coupling approximations, referred to as generalized Manakov equations. Finally, the chapter presents experimental observations of two inter-modal nonlinear effects, inter-modal cross-phase modulation, and inter-modal four-wave mixing, over a few-km-long few-mode fiber. Important differences between intra-modal and inter-modal nonlinear effects are also discussed.

2B Commercial 100-Gbit/s Coherent Transmission Systems

Tiejun J. Xia and Glenn A. Wellbrock

This chapter provides a global network service provider’s view on technology development and product commercialization of 100-Gbit/s for optical transport networks. Optical channel capacity has been growing over the past four decades to address traffic demand growth and will continue this trend for the foreseeable future to meet ever-increasing bandwidth requirements. In this chapter, optical channels are reclassified into three basic design types. Commercial 100-Gbit/s channel development experienced all three types of channel designs before eventually settling on the single-carrier polarization-multiplexed quadrature-phase-shift keying (PM-QPSK) format using coherent detection, which appears to be the optimal design in the industry. A series of 100-Gbit/s channel related field trials was performed in service providers’ networks to validate the technical merits and business advantages of this new capacity standard before its deployment. Introduction of the 100-Gbit/s channel brings new opportunities to boost fiber capacity, accommodates increases in client interface speed rates, lowers transmission latency, simplifies network management, and speeds up the realization of next-generation optical add/drop functions.

3B Advances in Tb/s Superchannels

S. Chandrasekhar and Xiang Liu

Optical superchannel transmission, which refers to the use of several optical carriers combined to create a channel of desired capacity, has recently attracted much research and development in an effort to increase the capacity and cost-effectiveness of wavelength-division multiplexing (WDM) systems. Using superchannels avoids the electronic bottleneck via optical parallelism and provides high per-channel data rates and better spectral utilization, especially in transparent mesh optical networks. This chapter reviews recent advances in the generation, detection, and transmission of optical superchannels with channel data rates on the order of Tbit/s. Multiplexing schemes such as optical orthogonal-frequency-division-multiplexing (O-OFDM) and Nyquist-WDM are described, in conjunction with modulation schemes such as OFDM and Nyquist-filtered single-carrier modulation. Superchannel transmission performance is discussed. Finally, networking implications brought by the use of superchannels, such as flexible-grid WDM, are also discussed.

4B Optical Satellite Communications

Hamid Hemmati and David Caplan

Current satellite-based communication systems are increasingly capacity-limited. Based on radio frequency or microwave technologies, current state-of-the-art satellite communications (Satcom) are often constrained by hardware and spectrum allocation limitations. Such limitations are expected to worsen due to the use of more sophisticated data-intensive sensors in future interplanetary, deep-space, and manned missions, an increased demand for information, and the demand for a bigger return on space-exploration investment. This chapter presents the recent advances in optical satellite communications technologies. Lasercom link budgets, the first step in designing a lasercom system, are discussed. The chapter then reviews the major challenges facing laser beam propagation through the atmosphere, including atmo-spheric attenuation, scattering, radiance, and turbulence. It also discusses mitigation approaches. The rest of the chapter focuses on optical transceiver technologies for satellite communications systems. Finally, space and ground terminals in optical satellite communications are discussed.

5B Digital Signal Processing (DSP) and its Application in Optical Communication Systems

Polina Bayvel, Carsten Behrens, and David S. Millar

The key questions in current optical communications research are how to maximize both capacity and transmission distance in future optical transmission networks by using spectrally efficient modulation formats with coherent detection and how digital signal processing can aid in this quest. There is a clear trade-off between spectral efficiency and transmission distance, since the more spectrally efficient modulation formats are more susceptible to optical fiber nonlinearities. This chapter illustrates the application of nonlinear back-propagation to mitigate both linear and nonlinear transmission impairments in a range of modulation formats at varying symbol rates, wavelength spacing, and signal bandwidth. The basics of coherent receiver structure and digital signal processing (DSP) algorithms for chromatic dispersion compensation, equalization, and phase recovery of different modulation formats employing amplitude, phase, and polarization are reviewed and the effectiveness of the nonlin-earity compensating DSP based on digital back-propagation is explored. This chapter includes a comprehensive literature review of the key experimental demonstrations of nonlinearity compensating DSP.

6B Advanced Coding for Optical Communications

Ivan B. Djordjevic

This chapter represents an overview of advanced coding techniques for optical communication. Topics include the following: codes on graphs, coded modulation, rate adaptive coded modulation, and turbo equalization. The main objectives of this chapter are as follows: (i) to describe different classes of codes on graphs of interest for optical communications, (ii) to describe how to combine multilevel modulation and channel coding, (iii) to describe how to perform equalization and soft-decoding jointly, and (iv) to demonstrate efficiency of joint demodulation, decoding, and equalization in dealing with various channel impairments simultaneously. The chapter describes both binary and nonbinary LDPC codes, their design, and decoding algorithms. A field-programmable gate array (FPGA) implementation of decoders for binary LDPC codes is discussed. In addition, this chapter demonstrates that an LDPC-coded turbo equalizer is an excellent candidate to simultaneously mitigate chromatic dispersion, polarization mode dispersion, fiber nonlinearities, and I/Q-imbalance. In the end, the information capacity study of optical channels with memory is provided for completeness of presentation.

7B Extremely Higher-Order Modulation Formats

Masataka Nakazawa, Toshihiko Hirooka, Masato Yoshida, and Keisuke Kasai

This chapter reviews recent progress on coherent quadrature amplitude modulation (QAM) and orthogonal frequency-division multiplexing (OFDM) transmission with higher-order multiplicity, which is aiming at ultra-high spectral efficiency approaching the Shannon limit. Key technologies are the coherent detection with a frequency-stabilized fiber laser and an optical PLL circuit. Single-carrier 1024 QAM and 256 QAM-OFDM transmissions are successfully achieved, demonstrating a spectral efficiency exceeding 10 bit/s/Hz. Such an ultra-high spectrally efficient transmission system would also play a very important role in increasing the total capacity of WDM systems and improving the tolerance to chromatic dispersion and polarization mode dispersion as well as in reducing power consumption. The chapter also describes a novel high-speed, spectrally efficient transmission scheme that combines the OTDM and QAM techniques, in which a pulsed local oscillator (LO) signal obtained with an optical phase-lock loop (OPLL) enables precise demultiplexing and demodulation simultaneously. An optimum OTDM and QAM combination would provide the possibility for realizing long-haul Tbit/s/channel transmission with a simple configuration, large flexibility, and low-power consumption.

8B Multicarrier Optical Transmission

Xi Chen, Abdullah Al Amin, An Li, and William Shieh

This chapter is an overview of multicarrier transmission and its application to optical communication. Starting with an introduction to historical perspectives in the development of optical multicarrier technologies, the chapter presents different variants of optical multicarrier transmission, including electronic and optical fast Fourier transform (FFT)-based realizations. In the next section, several problems of fiber nonlinearity in optical multicarrier transmission systems are highlighted and an analysis of fiber capacity under nonlinear impairments is presented. The applications of multicarrier techniques to long-haul systems, access networks, and free-space optical communication systems are also discussed. Finally, this chapter summarizes several possible directions for research into the implementation of multicarrier technologies in optical transmission.

9B Optical OFDM and Nyquist Multiplexing

Juerg Leuthold and Wolfgang Freude

New pulse shaping techniques allow for optical multiplexing with the highest spectral efficiencies. This chapter introduces the general theory of orthogonal pulse shaping followed by a discussion that places more emphasis on the orthogonal frequency division multiplexing (OFDM) and Nyquist frequency-division multiplexing schemes. Subsequently, the chapter shows that the rectangular-shaped pulses used for OFDM can mathematically be treated by the Fourier transform. This leads to the theory of the time-discrete Fourier transform (DFT) and to a discussion of practical implementations of the DFT and its inverse in the optical domain. The chapter concludes with exemplary implementations of OFDM transceivers that either rely on direct pulse shaping or use the DFT approaches.

10B Spatial Multiplexing Using Multiple-Input Multiple-Output Signal Processing

Peter J. Winzer, Roland Ryf, and Sebastian Randel

In order to further scale network capacities and to avoid a looming capacity crunch, space has been identified as the only known physical dimension yet unexploited for optical modulation and multiplexing. Space-division multiplexing (SDM) may use uncoupled or coupled cores of multi-core fiber, or individual modes of multimode waveguides. If crosstalk rises to levels where it cannot be treated as a transmission impairment any more, multiple-input multiple-output (MIMO) digital signal processing (DSP) techniques have to be used to manage crosstalk in highly integrated SDM systems. This chapter reviews the fundamentals and practical experimental aspects of MIMO-SDM. First, it discusses the importance of selectively addressing all modes of a coupled-mode SDM channel at transmitter and receiver in order to achieve reliable capacity gains. It shows that reasonable levels of mode-dependent loss (MDL) are acceptable without much loss of channel capacity. The chapter then introduces MIMO-DSP techniques as an extension of familiar algorithms used in polarization-division multiplexed (PDM) digital coherent receivers and discusses their functionality and scalability. Finally, the design of mode multiplexers that allows for the mapping of the individual transmission signals onto an orthogonal basis of waveguide mode is reviewed and its performance in experimental demonstrations is discussed.

11B Mode Coupling and its Impact on Spatially Multiplexed Systems

Keang-Po Ho and Joseph M. Kahn

Mode coupling is the key to overcoming challenges in mode-division multiplexed transmission systems in multimode fiber. This chapter provides an in-depth description of mode coupling, including its physical origins, its effect on modal dispersion (MD) and mode-dependent loss (MDL) or gain, and the resulting impact on system performance and implementation complexity. Strong mode coupling reduces the group delay spread from MD, minimizing the complexity of digital signal processing used for compensating MD and separating multiplexed signals. Likewise, strong mode coupling reduces the variations of MDL that arise from transmission fibers and inline optical amplifiers, thus maximizing average channel capacity. When combined with MD, strong mode coupling creates frequency diversity, which reduces the probability of outage caused by MDL and enables outage capacity to approach average capacity. The statistics of strongly coupled MD and MDL depend only on the number of modes and the variances of MD or MDL, and they can be derived from the eigenvalue distributions of certain random matrices.

12B Multimode Communications Using Orbital Angular Momentum

Jian Wang, Miles J. Padgett, Siddharth Ramachandran, Martin P.J. Lavery, Hao Huang, Yang Yue, Yan Yan, Nenad Bozinovic, Steven E. Golowich, and Alan E. Willner

Laser beams with a helical phase front, such as Laguerre-Gaussian beams, carry orbital angular momentum (OAM). Based on the fact that different OAM beams can be inherently orthogonal with each other, OAM multiplexing was introduced to provide an additional degree of freedom in optical communications, and further increase the capacity and spectral efficiency in combination with advanced multilevel modulation formats and conventional multiplexing technologies. This chapter provides a comprehensive review of multimode communications using OAM technologies. The fundamentals of OAM are introduced first, followed by the techniques for OAM generation, multiplexing/demultiplexing, and detection. The chapter then presents recent research into free-space communication links and fiber-based transmission links using OAM multiplexing with optical signal processing using OAM (data exchange, add/drop, multicasting, monitoring, and compensation). Future challenges for OAM communications are then discussed.

13B Transmission Systems Using Multicore Fibers

Yoshinari Awaji, Kunimasa Saitoh, and Shoichiro Matsuo

As the simplest form of space-division multiplexing (SDM), multi-core fiber (MCF) transmission technologies have been widely studied. Many types of MCFs exist, but the most common is Uncoupled MCF in which each individual core is assumed to be an independent optical path. The key issue in these systems is how to suppress the intercore crosstalk and the coupling/decoupling mechanism. Currently, many MCF varieties, coupling methods, splicing techniques, and transmission schemes have been proposed and demonstrated, and despite the fact that many of the component technologies are still in the development stage, MCF systems already present the capability for huge transmission capacities. In this chapter, these component technologies and the early experimental trials of MCF transmission are reviewed. First, an overview of medium- to long-haul MCF transmission and theories is provided. Second, coupling technologies between MCF-SMF and MCF-MCF are reviewed. Finally, several experimental demon strations, including transmission exceeding 100 Tbit/s and over 1000 km, are described.

14B Elastic Optical Networking

Ori Gerstel and Masahiko Jinno

Service provider (SP) networks are undergoing major changes. These changes imply that the optical layer will have to be low-cost, flexible, and reconfigurable. To properly address this challenge, flexible and adaptive networks equipped with flexible transceivers and network elements that can adapt to the actual traffic demands are needed. The combination of adaptive transceivers, a flexible grid, and intelligent client nodes enables a new elastic networking paradigm, allowing SPs to address the increasing needs of the network without frequently overhauling it. This chapter starts by looking at the challenges faced by the optical layer in the future. These challenges are fueled by the insatiable appetite for more bandwidth, coupled with a reduced ability to forecast and plan for such growth. Different enabling technologies, including flexible spectrum reconfigurable optical add/drop multiplexers (ROADM), bit rate variable transceivers, and the extended role of network control systems are reviewed. The concept of elastic optical network (EON) is envisioned and the benefits are highlighted by further comparing the EON to a fixed WDM system.

15B ROADM-Node Architectures for Reconfigurable Photonic Networks

Sheryl L. Woodward, Mark D. Feuer, and Paparao Palacharla

The deployment of reconfigurable optical add/drop multiplexers (ROADMs) is gradually transforming a transport layer made of point-to-point optical links into a highly interconnected, reconfigurable photonic mesh. To date, the widespread use of ROADMs has been driven by the cost savings and operational simplicity they provide to quasi-static networks (i.e. networks in which new connections are frequently set up but rarely taken down). However, new applications exploiting the ROADMs’ ability to dynamically reconfigure a photonic mesh network are now being investigated. This chapter reviews the attributes and limitations of today’s ROADMs and other node hardware. It also surveys proposals for future improvements, including colorless, non-directional, and contentionless add/drop ports. The application of reconfigurable networks is also discussed with emphasis on the backbone network of a major communications service provider. Finally, the chapter assesses which of these new developments is most likely to bring added value in the short and long future.

16B Convergence of IP and Optical Networking

Kristin Rauschenbach and Cesar Santivanez

Rapidly increasing network demand based on unpredictable services has driven research into methods to provide intelligent provisioning, efficient restoration and recovery from failures, and effective management schemes that reduce the amount of hands-on activity to plan and run the network. Integrating the service-oriented IP layer together with the efficient transport capabilities of the optical layer is a cornerstone of this research. Converged IP-optical networks are being demonstrated in large multi-carrier and multi-vendor venues. Research is continuing on making this convergence more efficient, flexible, and scalable. This chapter reviews the current key technologies that contribute to the convergence of IP and optical networks, and describes control and management plane technologies, techniques, and standards in some detail. Current research challenges and future research directions are also discussed.

17B Energy-Efficient Telecommunications

Daniel C. Kilper and Rodney S. Tucker

For many years, advances in telecommunications have been driven by the need for increased capacity and reduced cost. Recently, however, concerns about the rising energy use of telecommunications networks have brought the issue of energy efficiency into the mix for both equipment vendors and network operators. This chapter provides an overview of energy consumption in telecommunications networks. This chapter identifies the key contributors to energy consumption and the trends in the growth of energy consumption. The chapter also compares the performance of state-of-the-art equipment with theoretical lower bounds on energy consumption and points to opportunities for improving the energy efficiency of core metro and access networks. The potential of significantly improving energy efficiency in telecommunications is envisioned.

18B Advancements in Metro Regional and Core Transport Network Architectures for the Next-Generation Internet

Loukas Paraschis

The expanding role of Internet-based service delivery, and its underlying infrastructure of internetworked data centers, is motivating an evolution to an IP next-generation network architecture with a flatter hierarchy of more densely interconnecting networks. This next-generation Internet is required to cost-effectively scale to Zettabytes of bandwidth with improved operational efficiency, in an environment of increasing traffic variability, dynamism, forecast unpredictability, and uncertainty of future traffic types. This chapter explores the implications of this change in the metro regional and core transport network architectures, and the important advancements in optical, routing, and traffic engineering technologies that are enabling this evolution. The chapter accounts particularly for the increasingly important role of optical transport, and photonics technology innovations.

19B Novel Architectures for Streaming/Routing in Optical Networks

Vincent W.S. Chan

Present-day networks are being challenged by dramatic increases in the data rate demands of emerging applications. New network architectures for streaming/routing large elephant transactions will be needed to reduce costs and improve power efficiency. This chapter examines a number of possible optical network transport mechanisms, including optical packet switching, burst switching, and flow switching and describes the necessary physical layer, routing, and transport layer architectures for these transport mechanisms. Performance comparisons are made based on capacity utilization, scalability, costs, and power consumption.

20B Recent Advances in High-Frequency (>10 GHz) Microwave Photonic Links

Charles H.Cox, III and Edward I.Ackerman

The transmission of multi-band radio signals through optical fibers has attracted great attention recently due to its potential for cellular backhaul networks, mobile cloud computing, and wireless local area networks. As wireless services and technologies evolve into multi-gigabit radio access networks, their speed is increased, but the wireless coverage of a single access point is inevitably and dramatically reduced. As a result, the importance of >10 GHz radio-over-fiber techniques has been emphasized for the capability of expanding wireless coverage feasibility, and in the meantime reducing system complexity and operation expenditure, especially in the high-speed millimeter-wave regime. This chapter introduces the radio-over-fiber technique and its challenge to handle optical millimeter-wave generation, transmission, and converged multi-band systems. By exploring real-world system implementation and characterization, the unique features and versatile applications of radio-over-fiber technologies are investigated and reviewed to reach next-generation converged optical and wireless access networks.

21B Advances in 1-100 GHz Microwave Photonics: All-Band Optical Wireless Access Networks Using Radio Over Fiber Technologies

Gee-Kung Chang, Yu-Ting Hsueh, and Shu-Hao Fan

With the growing bandwidth demand for the last mile and last meter in the access network, radio-over-fiber (RoF) technology at millimeter-wave (mmW) band has been viewed as one of the most promising solutions to providing ubiquitous multi-gigabit wireless services with simplified and cost-effective base stations (BSs) and low-loss, bandwidth-abundant fiber optic networks. This chapter first outlines the general methods and types of optical mmW generation, and summarizes their advantages and disadvantages. Owing to ultra-wide bandwidth and protocol transparent characteristics, a RoF system can be utilized to simultaneously deliver wired and multi-band wireless services for both fixed and mobile users. In the rest of this chapter, several multi-band 60-GHz RoF systems are reviewed, including mmW with baseband, microwave, mmW with commercial wireless services in low RF regions, and 60-GHz sub-bands.

22B PONs: State of the Art and Standardized

Frank Effenberger

This chapter aims to describe the current state of the passive optical network (PON) technology, including both state-of-the-art systems that are currently under research in the laboratory and standardized systems that have been or soon will be described as an industry norm. A short introduction to the PON topic is given, to set the scene and provide the basic motivation for why PON is so important to fiber access. Then, each of the major technologies is reviewed, including time division multiplexing, video overlay, wavelength-division multiplexing, frequency-division multiplexing, and hybrid multiplexing. The focus of each review is at a system level to present a wide view of the whole range, and comparisons are made to different technologies.

23B Wavelength-Division-Multiplexed Passive Optical Networks (WDM PONs)

Y.C. Chung and Y. Takushima

Wavelength-division multiplexed passive optical network (WDM PON) has long been considered as an ultimate solution for a future optical access network capable of providing practically unlimited bandwidth to each subscriber. On the other hand, it is still considered to be too expensive for mass deployment. To solve this problem and to meet the ever-increasing demand for bandwidth, there have been numerous efforts to improve the competitiveness of WDM PON. This chapter reviews the current status and future direction of these WDM PON technologies. It first reviews various colorless light sources, which are critical for the cost-effective implementation of the optical network units (ONUs), and several representative network architectures proposed for WDM PONs. The chapter then reviews the recent research activities for the realization of high-speed (>10 Gb/s) and long-reach WDM PONs. Various fault monitoring and protection techniques are also reviewed, as they may be increasingly important in future high-capacity WDM PONs.

24B FTTX Worldwide Deployment

Vincent O’Byrne, Chang Hee Lee, Yoon Kim, and Zisen Zhao

Since the early 2000s, Fiber-to-the-X, where X refers to different meanings for to different operators, has taken off around the world and is seen as the main method to meet the continued growth in the broadband needs of residential and business customers. This chapter covers two types of architectures, including the shared network among many users and the point-to-point network, and the standing of the various technologies for access space. The status of FTTX and some of the issues that operators are facing around the world are discussed. The chapter then reviews technologies that have been deployed to date and the new technologies that are under consideration to meet their customers’ residential and business needs in the future.

25B Modern Undersea Transmission Technology

Jin-xing Cai, Katya Golovchenko, and Georg Mohs

Much progress has been made over the last few years in undersea optical fiber tele communication systems. Most importantly, coherent receivers have become practical, enabling polarization multiplexing and higher-order modulation formats with increased spectral efficiency. This chapter provides an overview of the progress in undersea transmission technology. After a brief general introduction to undersea systems and their unique challenges and design constraints, the principles of coherent transmission technologies are outlined. These include polarization multiplexing, linear equalizers, and multiple bits per symbol. The chapter then describes the use of strong optical filtering to help to improve spectral efficiency, and it reviews the techniques to mitigate the effects of inter-symbol interference. Higher-order modulation formats that can further increase spectral efficiency by increasing the number of bits per symbol are then introduced. The implications of the receiver sensitivity degradation and the mitigation techniques are discussed.

Ivan P. Kaminow

(Bell Labs, retired)

University of California, Berkeley, CA, USA

Tingye Li

(Bell Labs and AT&T Labs, deceased)

Boulder, CO, USA

Alan E. Willner

University of Southern California, Los Angeles, CA, USA

Chapter 1

Fiber Nonlinearity and Capacity: Single-Mode and Multimode Fibers

René-Jean Essiambre, Robert W. Tkach and Roland Ryf,    Bell Laboratories, Alcatel-Lucent, 791 Holmdel-Keyport Road, Holmdel, NJ 07733, USA

Acknowledgments

We would like to thank many colleagues and collaborators, in particular S. Mumtaz, A. Mecozzi, M.A. Mestre, G.P. Agrawal, G. Kramer, J. Foschini, A. Gnauck, P.J. Winzer, S. Randel, A. Chraplyvy, A. Tulino, M. Magarini and collaborators from OFS and Sumitomo electric company as well as many other colleagues inside and outside Bell Laboratories.

1.1 Introduction

The vast majority of all communications on the planet goes through a worldwide network of interconnected fused-silica optical fibers forming the backbone of optical networks. This fact results from important intrinsic advantages of optical fibers. A first critical property of fused-silica fiber is its wideband frequency region (∼40 THz) of low transmission loss (∼0.2–0.35 dB/km) centered around a carrier frequency of ∼200 THz. This broad low-loss frequency range allows a larger quantity of information to be transmitted [1] than in the narrower frequency bands available for other types of communication systems such as wireless (tens of MHz), digital subscriber lines (DSLs) (∼a few tens of MHz) and satellite communications (a few hundreds of MHz). A second advantage of optical fibers is that they provide tight spatial confinement of a few tens of micrometers that enables the use of multiple independent channels with great spatial density.

A fused-silica optical fiber is a medium that differs in a fundamental manner from other transmission media—it exhibits the optical Kerr effect [2,3], a nonlinear phenomenon that introduces distortions that increase with signal power. As a result, there exists a maximum quantity of information that can be transmitted through optical fibers (see [4–7] and references therein for single-mode fibers, SMFs). This maximum nonlinear capacity is often referred to as the nonlinear Shannon capacity limit that we abbreviate in this chapter to simply nonlinear capacity limit. The nonlinear capacity limit of a SMF depends on some of the fiber physical properties, such as loss and nonlinear coefficients and chromatic dispersion [7]. The nonlinear capacity limit of a 500-km-long system using the standard SMF (SSMF) is estimated to be between 70 Tb/s for a C-band system having 4 THz optical bandwidth and 175 Tb/s for 10 THz optical bandwidth for an extended C- and L-band system (see Section 1.5.2) [4].

Current backbone optical networks are exclusively based on SMFs and further capacity increase will eventually require installing new systems in parallel when we closely approach the nonlinear capacity limit of SMFs [4]. An alternative approach to parallel fibers is to consider fibers supporting multiple spatial modes to increase capacity [8]. Systems based on multimode fibers (MMFs) or multicore fibers (MCFs) have the potential to be of lower cost by making use of optical and electronic integrations while achieving greater spatial densities and reducing management complexity.

This chapter starts by providing some statistics on traffic demand in optical networks and the capacity scaling over time of commercial optical communication systems. These observations, in combination with the knowledge of a nonlinear capacity limit, suggest that a fiber capacity crunch may be looming [8]. This section is followed by a brief review of the basic results of information theory. We then describe the stochastic nonlinear Schrödinger equation (SNSE), the equation that governs nonlinear propagation in SMFs. This is followed by calculations of nonlinear capacity limit estimates for SSMF and for advanced fibers having improved transmission characteristics. An analytical formula of nonlinear capacity is also presented.

We then introduce a set of coupled partial differential equations (PDEs) describing nonlinear propagation of polarization-division multiplexed (PDM) signals in SMFs along with nonlinear capacity estimates for these systems. The next section focuses on MMFs and MCFs. We first present an elementary analysis of MMFs and MCFs capacities in the absence of fiber nonlinearity. The rest of the chapter focuses on nonlinear effects in MMFs and MCFs, with an emphasis on MMFs and few-mode fibers (FMFs). The impact of nonlinearity in fibers supporting multiple spatial modes is still an area with many unknowns, despite the fact that nonlinear effects in fibers were first observed using FMFs (see Ref. [9] for a historical review). The chapter concludes by reporting experimental observations of two important nonlinear effects between spatial modes: inter-modal cross-phase modulation (IM-XPM) and inter-modal four-wave mixing (IM-FWM).

1.2 Network Traffic and Optical Systems Capacity

The capacity of optical communication systems has seen an incredible growth since their inception four decades ago, increasing by more than a factor of 100,000 to reach today’s commercial systems capacities of nearly 10 Tb/s. The technological implementation of such a data carrying capacity in a single fiber was unimaginable in the early days of optical communications, and would have seemed far beyond the needs of society if it had been envisioned. But since the mid-1990s, the advent of the Internet and its associated applications has driven a growth rate in data traffic that challenges the ability of optical technology to keep up. Figure 1.1 shows the capacity of commercial optical communication systems versus their year of introduction (including a projected point at 17.6 Tb/s in 2013). Also shown is a curve corresponding to North American core network traffic based on 2009 traffic levels and measured growth rates [10]. The traffic curve is dominated by voice before 2000 and by data traffic after 2004. Plotting these two quantities on the same graph yields a striking observation: Traffic growth of roughly 50% per year is greatly outstripping the growth in the capacity of optical communications systems of less than 20% per year. Thus, while the entire traffic in the North American core network could be carried on a single fiber in 2008, in 2011 more than two fibers were required. If the growth trends continue as shown, the required number of fibers (and systems) will double every 3 years. While this situation may seem rosy for system vendors, it is frightening to their customers.

Figure 1.1 Commercial system capacities (squares and red curve) and total network traffic including voice (blue curve). The growth of network traffic currently exceeds the growth of systems capacity. For interpretation of the references to color in this figure legend, the reader is referred to the web version of this book.

Even these projected growth rates for system capacity are likely to be overly optimistic. If we examine the historical trends for system capacity we see a period of extremely rapid growth in the mid-1990s arising from the introduction of wavelength-division multiplexing (WDM). In those years, most of the capacity growth was achieved by simply expanding the number of WDM channels and concomitantly the occupied bandwidth of the erbium-doped fiber amplifiers (EDFAs). After the first systems with capacities of several hundred Gb/s were introduced, the bandwidth of the amplifiers was fully occupied. Further increases in capacity have come from increased efficiency in the use of the spectrum. This spectral efficiency (SE) is a familiar concept used in many other fields of communication, and particularly in wireless communication systems. It is expressed in bits per second per Hz. Figure 1.2shows the SE of the same commercial systems shown in Figure 1.1, plotted versus year. Up through the year 2000 all systems shown used