This text, authored by Allan W. Snyder and John D. Love, provides a comprehensive and self-contained treatment of optical waveguide theory. It is divided into three parts: Part I covers ray analysis of multimode optical waveguides, emphasizing geometrical and elementary ray methods. Part II delves into electromagnetic analysis, focusing on waveguides that propagate only one or a few modes, where the methods of Part I are less applicable. Part III offers supplementary mathematical methods to enhance the physical discussions in Parts I and II. The book includes over 150 problems with complete solutions and is designed to be accessible to undergraduates, with many fundamental topics presented for the first time. The authors aim to provide a unified treatment of basic ideas using the simplest approach possible, and they acknowledge the contributions of numerous individuals who helped in the development and refinement of the text.This text, authored by Allan W. Snyder and John D. Love, provides a comprehensive and self-contained treatment of optical waveguide theory. It is divided into three parts: Part I covers ray analysis of multimode optical waveguides, emphasizing geometrical and elementary ray methods. Part II delves into electromagnetic analysis, focusing on waveguides that propagate only one or a few modes, where the methods of Part I are less applicable. Part III offers supplementary mathematical methods to enhance the physical discussions in Parts I and II. The book includes over 150 problems with complete solutions and is designed to be accessible to undergraduates, with many fundamental topics presented for the first time. The authors aim to provide a unified treatment of basic ideas using the simplest approach possible, and they acknowledge the contributions of numerous individuals who helped in the development and refinement of the text.