visible light communication (VLC) is the branch of OWC employing white light or selected colors between violet and red. In a more strict sense, the key idea of VLC is to conduct joint illumination and data transmission by modulating the light source(s). This concept dates back to the beginning of this century. In 2001, Masao Nakagawa and members of his team at Keio University in Yokohama invented and explored the fascinating idea of using light simultaneously for illumination and communication purposes [Kom03, Kom04]. Quickly, researchers from all over the world began to investigate fundamentals and applications of VLC [Kom03, Kom04, Arn15, Dim15, Gha17, Wan17, Chi18]. In most cases light emitting diodes (LEDs) are utilized, which can be switched “on”and “off” more than a million times per second without significant impact on operating lifetime and aging. Medium-range VLC applications are dominant.
In this textbook, we are not just interested in VLC defined in the strict sense, because the
main principles, modulation and reception techniques, circuit designs etc. can also be applied to other light sources (like laser diodes, organic LEDs, and micro-LEDs) and to the adjacent frequency bands, namely infrared and ultraviolet. However, we do not consider optical fibers in any case.