Optoelectronics, a subfield of photonics, is the study and application of electronic equipment and systems that produce, detect and control light. In addition to visible light, it also includes the study and use of gamma rays, X-rays, ultraviolet rays and infrared rays. Optoelectronic devices can be optical-to-electrical or electrical-to-optical transducers, or devices that use such instruments in their working. Optoelectronics is centered on the quantum mechanical effects of light on electronic matter and involves the usage of concepts such as the photoelectric effect, photovoltaic effect, photoconductivity, stimulated emission, radiative recombination, etc. Optocoupler and optical fiber communications are some of the important applications of optoelectronics. This book traces the progress of this field and highlights some of its key concepts and applications. It is compiled in such a manner, that it will provide in-depth knowledge about the principles and practices of optoelectronics. Through this book, we attempt to further enlighten the readers about the new concepts in this field.