Preface

Optical communication is very much useful part in our advanced fibre-based telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters cover general concepts of optical communication, components for optical communication, optical communication systems and networks, signal processing and MIMO systems. In recent years, optical components and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on optical devices, networking, signal processing, and MIMO systems and other enhanced functions for optical communication. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries.

This book presents a high level technical overview of the emerging technologies of optical communication and networking systems. It is intended as an introduction to the field for optical communication and 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 or networking.

Figure 1 illustrates a simple schematic diagram of an optical communication system/ link. It consist of three separate parts, such as, (i) the transmitter contains a constant optical/ light source as laser and a modulator, (ii) the channel or link is an optical fiber about 100-kms long that carries the information from the transmitter to the receiver, and (iii) the receiver consists of a semiconductor photodetector that detects the received signal and an amplifier for the amplification of received signal from the channel/link. The optical pulses are created using lasers and transmitted through the transmitter via the links/channels and receiving at the receiver side. A list of bits (such as, '**1**'s and '**0**'s are as input data signal) are sent into the transmitter in the form of data/signal levels (high '1' or low '0'), where they control a modulator, which alters the power of a light beam produced by a light source or laser. The laser light source produces a constant-power light beam, which experiences different amount of

#### X Preface

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 '1' or low '0' 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, the following Fig. 1 covers all parts/ chapters concept of this book. These are: General Concepts, Optical Components, Systems, Networks, Signal Processing and MIMO Systems in optical communication.

**Figure 1.** A simple schematic diagram of an optical communication system/ link, where the transmitter contains a constant-power optical/light source as laser and a modulator, the channel/ link is an optical fiber about 100-kms, and the receiver consists of a semiconductor photodetector and 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 communication and networking. They cover a number of themes, which include the basic concepts of optical communication, components for optical communication such as amplifiers, optical communication systems and networks, signal processing and MIMO systems for optical communication 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 Communication: Part 1, General Concepts; Optical Communication: Part 2, Optical Components, such as Amplifiers and Lasers; Optical Communication: Part 3, Optical Systems, such as Transmission Systems; Optical Communication: Part 4, Optical Networks; Optical Communication: Part 5, Signal processing; Optical Communication: and Part 6, MIMO systems; Optical Communication. These categorisations of parts are not fully perfect because some of the chapters are mixed or overlapped i.e., like an inter-disciplinary 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 communication.

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

X Preface

and amplifier.

**Organisation of the Book** 

**Optical/ Light Source**

**Input Data bits** 

**010010101010** 

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 '1' or low '0' 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, the following Fig. 1 covers all parts/ chapters concept of this book. These are: General Concepts, Optical Components, Systems, Networks,

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

**fier Laser Modulator**

**Transmitter Receiver**

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

**Photodetector**

**Optical Pulses Output Data bits** 

**Ampli-**

**010010101010** 

The authors with whom I have had the pleasure to collaborate have written chapters that report recent developments in optical communication and networking. They cover a number of themes, which include the basic concepts of optical communication, components for optical communication such as amplifiers, optical communication systems and networks, signal processing and MIMO systems for optical communication 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

In this book, the chapters have been grouped as part according to the following themes: Optical Communication: Part 1, General Concepts; Optical Communication: Part 2, Optical Components, such as Amplifiers and Lasers; Optical Communication: Part 3, Optical Systems, such as Transmission Systems; Optical Communication: Part 4, Optical Networks; Optical Communication: Part 5, Signal processing; Optical Communication: and Part 6, MIMO systems; Optical Communication. These categorisations of parts are not fully perfect because some of the chapters are mixed or overlapped i.e., like an inter-disciplinary topic. However, all of the chapter are within an easily identifiable subject boundary that is a positive sign of the indicators of

Signal Processing and MIMO Systems in optical communication.

range of topics that we have been able to include in this book.

scientific progress in optical communication.

I acknowledge to Professor Sven Nordholm, Head, Department of Electrical and Computer Engineering, Professor Syed Islam, 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 also acknowledge to Dr Mohammad Razaghi, University of Kurdistan, Iran for his continuous support, encouragement and collaboration to complete this book.

I am very much grateful to Ms. Jana Sertic, Mr. Dejan Grgur and Mr. Oliver Kurelic, publishing process managers at Intech, for their 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 this book.

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

**Optical Communication: General Concepts** 

**Chapter 1** 
