Telecommunications that use light as the transmission medium is
called optical communication. In this form of communication
transmitters encode a message into light as an optical signal, which is
transported to a receiver. The receiver returns the message to its
original understandable form.
Basic forms of optical communication has been around for a long
time, such as the use of signal lamps by the Navy and Aldis lamps to
communicate distress messages. Today, we use optical applications,
such as optical fibers that send messages over cables and free-space
optics that communicate over short distances.