Page 16 - Fiber Optic Communications Fund

Preface

The field of fiber-optic communications has advanced significantly over the last three decades. In the early
days, most of the fiber’s usable bandwidth was significantly under-utilized as the transmission capacity was
quite low and hence, there was no need to apply techniques developed in non-optical communication sys-
tems to improve the spectral efficiency. However, with the recent revival of coherent detection, high spectral
efficiency can be realized using advanced modulation formats.
This book grew out of our notes for undergraduate and graduate courses on fiber-optic communications.
Chapters 1 to 6 discuss, in depth, the physics and engineering applications of photonic and optoelectronic
devices used in fiber-optic communication systems. Chapters 7 to 11 focus on transmission system design,
various propagation impairments, and how to mitigate them.
Chapters 1 to 7 are intended for undergraduate students at the senior level or for an introductory gradu-
ate course. The sections with asterisks may be omitted for undergraduate teaching or they may be covered
qualitatively without the rigorous analysis provided. Chapters 8 to 11 are intended for an advanced course
on fiber-optic systems at the graduate level and also for researchers working in the field of fiber-optic com-
munications. Throughout the book, most of the important results are obtained by first principles rather than
citing research articles. Each chapter has many worked problems to help students understand and reinforce
the concepts.
Optical communication is an interdisciplinary field that combines photonic/optoelectronic devices and
communication systems. The study of photonic devices requires a background in electromagnetics. There-
fore, Chapter 1 is devoted to a review of electromagnetics and optics. The rigorous analysis of fiber modes
in Chapter 2 would not be possible without understanding the Maxwell equations reviewed in Chapter 1.
Chapter 2 introduces students to optical fibers. The initial sections deal with the qualitative understanding of
light propagation in fibers using ray optics theory, and in later sections an analysis of fiber modes using wave
theory is carried out. The fiber is modeled as a linear system with a transfer function, which enables students
to interpret fiber chromatic dispersion and polarization mode dispersion as some kind of filter.
Two main components of an optical transmitter are the optical source, such as a laser, and the optical mod-
ulator, and these components are discussed in Chapters 3 and 4, respectively. After introducing the basic
concepts, such as spontaneous and stimulated emission, various types of semiconductor laser structures are
covered in Chapter 3. Chapter 4 deals with advanced modulation formats and different types of optical mod-
ulators that convert electrical data into optical data. Chapter 5 deals with the reverse process – conversion
of optical data into electrical data. The basic principles of photodetection are discussed. This is followed
by a detailed description of common types of photodetectors. Then, direct detection and coherent detection
receivers are covered in detail. Chapter 6 is devoted to the study of optical amplifiers. The physical principles
underlying the amplifying action and the system impact of amplifier noise are covered in Chapter 6.