Optical telecommunication is any form of telecommunication that uses light as the transmission medium. It can be performed visually or it can be undertaken in an electronic form. The earliest forms of optical telecommunications date back several millennium. The earliest electrical form of optical telecommunication was the photophone, invented in 1880.
An optical telecommunication system uses a transmitter, which encodes a message into an optical signal (information theory)|signal, a channel (communications)|channel, which carries the signal to its destination, and a Tuner (radio)|receiver, which reproduces the message from the received optical signal.Free space optical communication|Free space optical telecommunication has been deployed in space, while terrestrial forms are naturally limited by geography, weather and the availability of light. This article will provide a basic introduction to some of the different forms that optical telecommunications have been deployed in.