This book provides a thorough review of multi-mode propagation inside optical waveguides and free space, which is receiving particular attention for its promising applications in communications and sensing. At the heart of the book is the matter of how modes couple and interfere due to engineered or random index fluctuations, forming functional devices.

The chapters cover topics such as multi-mode interference, coupled mode theory, and mode generation. Readers discover how a universal coupled mode theory can describe mode propagation, enabling stochastic analysis and avoiding...