Photonic systems, and photonic switching systems in particular, have captured the imagination of the telecommunications industry. With the introduction of advanced fiber in the network, with the acceptance of synchronous optical networks (SONET) replacing the older proprietary asynchronous systems, and with future multimedia services requiring ever more bandwidth, device designers are trying to obtain ever higher data rates. The assumed market demand for all of this is due to several considerations, including greater bandwidth needed for digital video, distributed interactive industrial design, and ever-increasing general public communications needs. The traditional carriers have concerns relating to their core business as new competitors emerge. Even the US government is entering the fray with its “information superhighway” initiatives.
Hinton has thus produced a timely book. He and his collaborators (J. R. Erickson, T. J. Cloonan, F. A. P. Tooley, F. B. McCormick, and A. L. Lentine) have gathered a wealth of facts about the subject. After a short introduction on general switching systems, the five remaining chapters divide the subject into optically transparent devices, optically transparent systems, optical logic devices, free-space optical hardware, and photonic switching architectures based on logic devices using free-space digital optics.
The book is very readable; the several digressions into background items, such as a 40-page discussion of general optical imaging problems, only add to its completeness. The book could be the basis for a graduate-level introduction to the subject. Each chapter concludes with a set of exercises and a complete set of references (about 100 per chapter).
As someone reasonably versed in the field, I read the book straight through. Practitioners in the field would profit from the experience. For novice graduate students, the book presents a challenge. Several hundred different devices are presented. While each device is presented briefly, the mathematical basis for most devices must be found in the reference material. If the student is too thoughtful, the mathematical digressions would consume a great deal of energy. The challenge for students can be softened if the teacher is well read in the subject and can choose where to go into more detail.
After reading the book, one comes away with the feeling of being on some frontier of engineering application. Certainly, when the field is reduced to practice, many devices will be winnowed out. In fact, the author takes no sides. The promises and shortcomings of each device are enumerated. The closest the author comes to predicting the future comes in the final chapter, in Section 6.4.6, where he states:
it is practically impossible to predict the future in a field that is growing and changing as rapidly as free-space photonic switching [but]…smart pixels…will permit very large networks to be constructed.…Micro-optics,…wave mixing,…[and] holograms will become common.…In general, the field of free-space photonic switching is still in its infancy, but it is a rapidly growing field that will continue to improve over time.
It will be interesting to see which (if any) of the devices described becomes the basic building block of 21st-century switching systems.
One question remains. The introductory chapter gives the size of the need. Figure 1.2 shows the traffic characteristics of broadband services. The major high-speed (over 107 bits/second and long connect times) needs are information retrieval, conference video, and especially entertainment video. The recent commotion over high definition television may subside. High quality video may actually need less than 107 bits/second. In this case, one of the main drivers may be lacking.
The book has only a few shortcomings. The large number of devices confuses the reader, and the author’s refusal to espouse a winner left me feeling depressed. Is there ever going to be a successful set of devices? Each device treated seems to have a fatal flaw. The index is only two and a half pages long. Figures 6.7 (a) and 6.7 (b) are the same. Finally, the author treats the subject of blocking in a confusing way. He introduces non-blocking with a comparison of a 64×64 non-blocking crossbar network requiring 1012 crosspoints. This confuses the question; such a network would not only be non-blocking, it would allow each input to reach all outputs all the time. This requirement is too strong. Only later in the section does the author return to the blocking question and treat it correctly.
Notwithstanding the above reservations, this book is good and should find an eager readership.
