Optical communications networks are becoming increasingly important as there is a demand for high capacity links. Dense wavelength division multiplexing (DWDM) is widely deployed in core networks to accommodate high capacity transport systems. Optical components such as optical amplifiers, tunable filters, transceivers, termination devices and addition-drop multiplexers are becoming more reliable and affordable. Access networks and metropolitan area are increasingly built with optical technologies to overcome the electronic bottleneck at the edges of the network. New components and subsystems for very high-speed optical networks offer new design options.
Optical communication, also known as optical telecommunication, is the remote communication using light to convey information. It can be done visually or by electronic devices. The first basic forms of optical communication go back several millennia, while the first electrical device created to do so was the photophone, invented in 1880.
An optical communication system uses a transmitter encoding a message in an optical signal, a channel that carries the signal to its destination and a receiver that reproduces the message from the received optical signal. When electronic equipment is not used, the "receiver" is a person who visually observes and interprets a signal, which may be simple (such as the presence of a light beacon) or complex (such as lights using color codes or showing A Morse code sequence).
Optical communication in free space has been deployed in space, while terrestrial forms are naturally limited by geography, climate and the availability of light. This article provides a basic introduction to the different forms of optical communication.