The Advanced Study Institute on Fiber and Integrated Optics was held at Cargese from June 23 to July 7, 1978, at a time when both fields were undergoing a very rapid evolution. Fiber optics communications systems, in a multimode form, are moving out of laboratories and into practical use, and integrated optics is beginning to produce high performance, single-mode devices. In addition, the spin-off from the technological developments in both fields is beginning to have a growing impact on the general field of experimental physics. The lectures given at Cargese and assembled here illustrate these points and will be of considerable interest to both newcomers and people already in these fields. The lectures in the first eight chapters of the book deal with fiber and optical communications. The second section, chapters 9-13, is devoted essentially to integrated optics. The third section, chapters 14-17, is devoted to technical seminars and the remaining chapters, 18-22, to national reviews and economic aspects of fiber systems. On behalf of the organizing committee, which included Drs. Unger, Arnaud, Scheggi, and Daino, I would like to thank the Scientific Affairs Division of NATO, and in particular its director, Dr. T. Kester, for enabling this Advanced Study Institute to be held. In addition, we would like to offer a very heartfelt thanks to Marie-France Hanseler, who, aided by Aline Medernach and G. Sala, created the memorable atmosphere that pervaded the Institute.