The propagation of electromagnetic waves in "square-law" media, i.e., media characterized by a quadratic spatial variation of the dielectric constant, has been a favorite subject of investigation in electromagnetic theory. However, with the recent fabrication of glass fibers with a quadratic radial variation of the dielectric constant and the application of such fibers to optical imaging and communications, this subject has also assumed practical importance. Comparison of experimental results on propagation, resolu tion, and pulse distortion in such inhomogeneous waveguides with theory has put the field on a sound base and spurred further work. The present book aims at presenting a unified view of important aspects of our knowledge of inhomogeneous optical waveguides. A brief discussion of homogeneous dielectric waveguides is unavoidable, since itforms a basis for the appreciation of inhomogeneous waveguides. A short course based on some chapters of this book was offered to graduate students at IIT Delhi and was well received. We consider that despite the unavoidable mathemati cal nature of the present book, the comparison of experimental results with theory throughout and the description of fabrication technology (Appen dixes A and B) should make its appeal universal. The authors are grateful to Dr. K. Thyagarajan for writing most of Chapter 9 and to their colleagues Dr. I. C. Goyal, Dr. B. P. Pal, and Dr. A.