The rapidly growing importance of optical fibers as a communications medium has been accompanied by a steady improvement of the theoretical understanding of their properties. In the beginning, basic physical and mathematical principles allowed only a rough description of fiber behavior. Later on, more precise theories were developed, but most of them are highly complex and can only be used by specialists, and their apparent accuracy is not always supported by the achievable precision of parameter measurements. Eventually, more realistic theories evolved (influenced by the growing knowledge of physical effects in fibers) which could be used more easily and which were nevertheless of sufficient accuracy. This book concentrates on these types of methods, some of which are not yet generally known, because they are of particular interest to engineers and students of communications, for whom it was mainly written. I am glad that in addition to the original German version it is now also available in English and thus can reach a far greater audience.

The main topic of this book is the description and calculation of the transmission properties of optical fibers for communications, but it also describes those properties of optical sources and detectors that are important for systems designers and the systems properties resulting from these elements. The methods described were selected so as to explain observable properties of fibers and systems in a relatively simple way, and to show how these properties can be measured, predicted, or influenced in practice.

To assist in understanding, these theories are presented with the emphasis on their physical meaning rather than on mathematical details, but of course their results are mathematical formulae. The evaluation of these is not always straightforward; sometimes intricate algorithms are needed, and to demonstrate such algorithms, computer programs have been included in an appendix. They also support the practical application of the described theories, as they can easily be translated into workable versions for various computers (primarily in BASIC, but also for example in FORTRAN or PASCAL), and they have been tested both on powerful laboratory computers and on simple home computers.

In the writing of this book I was able to use the results of many years of my own scientific work, as well as the experience of numerous colleagues in the research laboratories and in the communications division of Siemens AG. An additional and important source of information were the Workshops on Optical Waveguide Theory held annually under the auspices of The European Conference on Optical Communication (ECOC), where I was able to have extensive discussions with leading scientists from many countries.

I thank all those who contributed to this book, and especially the following: Miss Uta Branczik, who carefully drew all the illustrations; the publishers; the translators for the preparation of the English version; and my wife and children for their patience and understanding.

Geckeler S (1987) Optical fiber transmission system.

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