The branch of physics that studies the properties of light and its interactions with matter is known as optics. Lenses, mirrors, fiber optics, lasers, telescopes and microscopes are some of the common applications of optical systems. Optical wireless communications is a form of optical communication. It uses unguided visible, ultraviolet and infrared light for carrying a signal. The wireless communication that operates in the visible region of the electromagnetic spectrum is known as visible light communication. This form of communication has applications in wireless local area networks, chip-to-chip communications, underwater communications, etc. At near infrared frequencies, communication is achieved using free space optical systems. The ever-growing need of advanced technology is the reason that has fueled the research in the fields of optical systems and wireless communications in recent times. This book is a valuable compilation of topics, ranging from the basic to the most complex advancements in these fields. The extensive content of this book will provide the readers with a thorough understanding of the subject.