Optical communications

Optical communication or optical telecommunication (sometimes known as optical transmission), is communication at a distance using light to carry information. Optical communication can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880. Modern communication relies on optical networking systems using optical fiber, optical amplifiers, lasers, switches, routers, and other related technologies. Free-space optical communication use lasers to transmit signals in space, while terrestrial forms are naturally limited by geography and weather. An optical communication system uses a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. When electronic equipment is not employed the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a Morse code sequence). Modern optical communication processes also may include optical encoding, optical data processing, optical modulation, and optical decoding.