In an exemplary and interdisciplinary form, this book deals with basic methods for the calculation and design of optical communication systems and sensor networks. The knowledge presented according to system-theoretical aspects covers the subareas of transmission, measurement, and processing of optical signals as input or output quantities of laser diodes, single-mode optical waveguides, photodiodes, optical modulators and couplers, fiber-optic amplifiers and polarizers, transmission systems with direct or heterodyne reception, and single-mode sensor networks based on interferometry or polarimetry. This book supports both practicing engineers and university teaching by summarizing fundamentals of optical communications and sensor technology, considering modern components and algorithms for signal analysis.