Once again it has become necessary to produce a new edition in order to update material provided in earlier editions and to add new descriptions of recently emerging technology. All of the chapters have been revised to inc1ude new developments, and to incorporate additionalliterature references. In the past few years there has been a vast expansion of worldwide telecom munications and data transmission networks. In many localities fiber-to-the-home and integrated services digital networks (ISDN) have become a reality .. Many people are now logging-on to the Internet and the World Wide Web. The growth of these networks has created a strong demand for inexpensive, yet efficient and reliable, integrated optic components such as signal splitters, couplers and multiplexers. Be cause of this demand, there has been a great deal of work recently on devices made using polymers and glas ses. Descriptions of these components have been added to the book in the appropriate chapters. A number of new practice problems have been added, and an updated booklet of problem solutions is available. The supplementary series of videotaped lectures de scribed in the preface to earlier editions continues to be available. Inquires regarding these materials should be sent directly to the author. The author wishes to thank Mrs. Barbara Westog, who helped with the organi zation of new material and typed the revisions.