**Optical Communications Systems**

Optical Communications Systems are very much essential part in our advanced fibre-based telecommunications and networks. They consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its destination, and a receiver that reproduces the message from the received optical signal. This book presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. Its chapters cover general concepts of optical and wireless optical communication systems, optical amplifiers and networks, optical multiplexing and demultiplexing for optical communication systems, and network traffic engineering. Recently, wavelength conversion and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on wavelength conversion, switching, demultiplexing in the time domain and other enhanced functions for optical communications systems. This book is targeted at research, development and design engineers from the teams in manufacturing industry; academia and telecommunications service operators/ providers.

This book presents a high level technical overview of the emerging technologies of optical communications and networking systems. It is intended as an introduction to the field for optical communication systems or network professionals, such as higher degree research students, academics and design engineers. Although it is intended for professionals who already have some technical background, it is nevertheless relevant to anyone wishing to understand optical communication systems or networks.

Figure 1 illustrates a simple schematic diagram of an optical communication system. It consist of three separate parts, namely, the transmitter contains a constant-power light source as laser and a modulator, the channel is an optical fiber about 100-kms that carries the information from transmitter to receiver, and the receiver consists of a semiconductor photodetector that detects the received signal and an optical amplifier for the amplification of received signal. Optical pulses are created using lasers/ amplifiers and transmitted through the transmitter via channels and receiving at the receiver. A list of bits ('**1**'s and '**0**'s as an input signal) are sent into the transmitter in the form of signal levels (high or low), where they control a modulator, which alters the power of a light beam produced by a light source (laser or amplifier). The light source (laser or amplifiers) produces a constant-power light beam, which experiences different amount of attenuation as it passes through the modulator, depending on the bit value is being sent. The light emerging from the modulator is a series of optical pulses of high or low power levels. These optical pulses travel as far as ~100-kms by total internal reflection inside the core of the fiber until they reach at the other end, where they are focused onto a light detector (as a semiconductor photodetector that detects the received signals). In general, Fig. 1 covers all parts/ chapters' concept of this book. These are: General Concepts, Amplifiers and Networks, Optical Multiplexing and Demultiplexing and Network Traffic.

Preface XI

**Narottam Das** 

Australia

I acknowledge to all authors for their contribution of book chapters from different

I acknowledge to Professor Syed Islam, Head, Department of Electrical and Computer Engineering, Curtin University, Perth, Australia and Professor Daryoush Habibi, Head of School of Engineering, Edith Cowan University, Perth, Australia for their

I am very much grateful to Ms Maja Kisic, publishing process manager at Intech, for her prompt responses to my queries. I wish all of my collaborators every success in

Foremost' I would like to thank my wife Varoti Sarkar for her patience'

Department of Electrical and Computer Engineering, Curtin University, Perth,

understanding, encouragement, and continuous support to complete the book.

organisations (Universities and industries).

their future research activities.

continuous support and encouragement to complete this task.

Fig. 1. A simple schematic diagram of an optical communication system, where the transmitter contains a constant-power light source as laser and a modulator, the channel is an optical fiber about 100-kms, and the receiver consists of a semiconductor photodetector and an optical amplifier.

## **Organisation of the Book**

The authors with whom I have had the pleasure to collaborate have written chapters that report recent developments in optical communications systems. They cover a number of themes, which include the basic optical communications systems, multiplexing and demultiplexing, traffic engineering, amplifiers and optical networks design as described above. No book of the current length can encompass the full scope of the subject but I am pleased at the range of topics that we have been able to include in this book.

In this book, the chapters have been grouped as part according to the following themes: Optical Communications Systems: Part 1, General Concepts; Optical Communications Systems: Part 2, Amplifiers and Networks; Optical Communications Systems: Part 3, Optical Multiplexing and Demultiplexing; Optical Communications Systems: Part 4, Network Traffic. These categorisations of parts are not fully perfect because some of the chapters are mixed i.e., like an interdisciplinary topic. However, all of the chapter are within an easily identifiable subject boundary that is a positive sign of the indicators of scientific progress in optical communications systems.

I acknowledge to all authors for their contribution of book chapters from different organisations (Universities and industries).

X Preface

and Demultiplexing and Network Traffic.

**010010101010** 

photodetector and an optical amplifier.

optical communications systems.

**Organisation of the Book** 

**Light Source Laser Modulator**

**Input Signal bits**

**Transmitter**

in this book.

the form of signal levels (high or low), where they control a modulator, which alters the power of a light beam produced by a light source (laser or amplifier). The light source (laser or amplifiers) produces a constant-power light beam, which experiences different amount of attenuation as it passes through the modulator, depending on the bit value is being sent. The light emerging from the modulator is a series of optical pulses of high or low power levels. These optical pulses travel as far as ~100-kms by total internal reflection inside the core of the fiber until they reach at the other end, where they are focused onto a light detector (as a semiconductor photodetector that detects the received signals). In general, Fig. 1 covers all parts/ chapters' concept of this book. These are: General Concepts, Amplifiers and Networks, Optical Multiplexing

Fig. 1. A simple schematic diagram of an optical communication system, where the transmitter contains a constant-power light source as laser and a modulator, the channel is an optical fiber about 100-kms, and the receiver consists of a semiconductor

**Optical Fiber (~ 100 kms) Channel**

**Photodetector**

**Optical Pulses Output Signal bits**

**Optical Amplifier** **010010101010** 

**Receiver**

The authors with whom I have had the pleasure to collaborate have written chapters that report recent developments in optical communications systems. They cover a number of themes, which include the basic optical communications systems, multiplexing and demultiplexing, traffic engineering, amplifiers and optical networks design as described above. No book of the current length can encompass the full scope of the subject but I am pleased at the range of topics that we have been able to include

In this book, the chapters have been grouped as part according to the following themes: Optical Communications Systems: Part 1, General Concepts; Optical Communications Systems: Part 2, Amplifiers and Networks; Optical Communications Systems: Part 3, Optical Multiplexing and Demultiplexing; Optical Communications Systems: Part 4, Network Traffic. These categorisations of parts are not fully perfect because some of the chapters are mixed i.e., like an interdisciplinary topic. However, all of the chapter are within an easily identifiable subject boundary that is a positive sign of the indicators of scientific progress in

I acknowledge to Professor Syed Islam, Head, Department of Electrical and Computer Engineering, Curtin University, Perth, Australia and Professor Daryoush Habibi, Head of School of Engineering, Edith Cowan University, Perth, Australia for their continuous support and encouragement to complete this task.

I am very much grateful to Ms Maja Kisic, publishing process manager at Intech, for her prompt responses to my queries. I wish all of my collaborators every success in their future research activities.

Foremost' I would like to thank my wife Varoti Sarkar for her patience' understanding, encouragement, and continuous support to complete the book.

**Narottam Das**  Department of Electrical and Computer Engineering, Curtin University, Perth, Australia

**Part 1** 

**General Concepts** 

**Optical Communications Systems:** 
