Optical communication

Optical communication is any form of telecommunication that uses light as the transmission medium.
An optical communication system consists of a transmitter, which encodes a message into an opticalsignal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal.
Forms of optical communication

Early opticalcommunication
There are many forms of non-technological optical communication, including body language and sign language.
Techniques such as semaphore lines, ship flags, smoke signals, and beacon fires werethe earliest form of technological optical communication.
The heliograph uses a mirror to reflect sunlight to a distant observer. By moving the mirror the distant observer sees flashes of light thatcan be used to send a prearranged signaling code. Navy ships often use a signal lamp to signal in Morse code in a similar way.
Distress flares are used by mariners in emergencies, while lighthousesand navigation lights are used to communicate navigation hazards.
Aircraft use the landing lights at airports to land safely, especially at night. Aircraft landing on an aircraft carrier use asimilar system to land correctly on the carrier deck. The light systems communicate the correct position of the aircraft relative to the best landing glideslope. Also, many control towers still have anAldis lamp to communicate with planes whose radio failed.
Optical fiber is the most common medium for modern digital optical communication.
Free-space optical co Optical fiber communication
Mainarticle: Fiber-optic communication.
Optical fiber is the most common type of channel for optical communications, however, other types of optical waveguides are used within computers or communications gear,and have even formed the channel of very short distance (e.g. chip-to-chip, intra-chip) links in laboratory trials. The transmitters in optical fiber links are generally light-emitting diodes...