Optical communication is any form of telecommunication that uses light as the transmission medium. Having originated in ancient times in the form of beacon fires and smoke signals that convey a message, optical wireless communication (OWC) has evolved to a high-capacity complementary technology to radio frequency (RF) communication. OWC systems utilize wavelengths in the infrared (IR) spectrum for IR communication and the visible light spectrum for visible light communication (VLC). Because of the availability of a huge license-free spectrum of approximately 670 THz, OWC has the potential to provide wireless links with very high data rates. In this book, optical modulation schemes, as well as signal processing and networking techniques, are presented to maximize the throughput of optical wireless networks using off-the-shelf components.
History of OWC
Examples of OWC in the form of beacon fires and smoke signals to convey a message can be found in almost all cultures. Semaphore lines are the earliest form of technological application of OWC . The French engineer Claude Chappe built the first optical telegraph network in 1792. His semaphore towers enabled the transmission of 196 information symbols encoded in the position of two arms connected by a crossbar. As another example of early OWC, the heliograph is a wireless solar telegraph that signals flashes of sunlight by pivoting a mirror or interrupting the beam with a shutter. After the invention of the Morse code in 1836, navy ships communicated by means of a signal lamp with on-shore lighthouses for navigation. In 1880, Alexander Graham Bell demonstrated the first implementation of a free-space optical (FSO) link in the form of the photophone . By using a vibrating mirror at the transmitter and a crystalline selenium cells at the focal point of a parabolic receiver, Bell was able to modulate a voice message onto a light signal.
The recent advancements in OWC technology gained significant pace after the pioneering work of Gfeller and Bapst in 1979 .