There are many excellent books in the area of fiber-optic communication systems. This book tackles one important subset of this broad field: fiber optic test and measurement techniques. It focuses specifically on the measurement and testing of fiber-optic communication links and the components that make up the link. This book also demonstrates methods to characterize the interactions between these components that have dramatic effects on system performance. The area of lightwave measurement technology is rapidly evolving as is the entire fiber optics industry. It is difficult to keep up with the myriad of measurement demands generated in both the telecommunications and data communications area. The contents of this book provide a detailed coverage of measurement principles that are needed to design and maintain fiber optic systems now and in the future.
It became clear to the authors of this book that no single source of information is available in the broad subject area of lightwave test and measurement for fiber optic systems. The authors are with the lightwave test and measurement divisions at HewlettPackard. This book combines the collective experience of the lightwave staff at HewlettPackard together in a single source. The material in this book has been developed from application notes, seminars, conference presentations, journal publications, Ph.D. theses, and unpublished works from the last ten years. Much of this material has not had wide circulation to date.
The book will be useful for technicians, engineers, and scientists involved in the fiber optics industry or who want to become familiar with it. The book is designed to address the needs of people new to the field and to those intimately familiar with it. Chapter
1 describes the operation of a fiber optic link and its components. It then briefly describes the most common measurement needs of the fiber optic link and components with measurement block diagrams and example results. The chapter will be particularly valuable for the reader who wants a basic introduction but is not ready to dive into the more detailed coverage given in the following chapters. The basic concepts of the measurements will be presented with a minimum of mathematical detail. The main chapters of the book are designed so that the first section of each chapter provides an overview. Graphical aids are used whenever possible to help in understanding. Later sections of each chapter are geared to cover the material in greater depth for more advanced readers.
Chapters 2 to 6 cover the fundamental areas of fiber optic measurements:
- a. Optical power measurements (Chapter 2);
b. Spectral measurements (Chapter 3 to 5);
c. Polarization measurements (Chapter 6).
The measurement of power is fundamental to most every lightwave measurement. Chapter 2 covers methods of power measurement and associated accuracy concerns. The area of optical spectral measurements is quite broad and is divided into three chapters. Chapter 3 covers the most common method using a diffraction-grating based optical spectrum analyzer. Chapter 4 covers the area of wavelength meters. Wavelength meters are the electrical analogue of frequency counters because they allow very accurate measurements of laser wavelength. Chapter 5 covers the area of very high wavelength-resolution spectral measurements.
The coverage of polarization in fiber optic systems (Chapter 6) is an area that historically has been underemphasized. This situation has changed since data rates have increased and optical amplifiers have been installed into fiber optic systems.
Chapters 7 and 8 focus on the measurement of the modulation on lightwave signals. In Chapter 7, the emphasis is on frequency-domain analysis of intensity modulation. The measurement of laser modulation bandwidth, distortion, and intensity noise are covered. Chapter 8 discusses time-domain measurements of the modulation. Here subjects such as eye-diagram analysis, temporal signal jitter, and bit-error-ratio measurements are covered.
Chapters 9 to 13 cover measurement topics that are common to two-port optical devices. Two-port optical devices include optical fiber, optical amplifiers, filters, couplers, isolators, and any other device where light enters and leaves. Chapter 9 covers the techniques used to measure insertion loss. Chapter 10 and I I cover methods of measuring the reflectivity of components. Chapter 12 covers the measurement of chromatic and polarization mode dispersion. Finally, Chapter 13 covers erbium-doped fiber amplifier (EDFA) testing.