Optical transmission utilizing injection light sources

Although a large amount of work in optical transmission has been accomplished through the use of lasers, modern developments have enabled noncoherent light sources also to be used in this area with great success. In particular, injection light sources-in the form of the coherent injection laser and the noncoherent light-emitting diode (LED)-offer designers of optical transmission systems characteristics that are in many ways superior to those of other methods. The present article deals essentially with how injection light sources may be employed to transmit or ``communicate'' information optically. Such optical techniques can be used not only in communication systems, in the classic RF sense, but in computer, video, telemetry, and detection systems as well.