Optron

a device that consists of a light-emitter and a photodetector that are optically coupled and are placed in a common envelope. Sometimes a light-emitter-photodetector pair with any kind of optical or electrical coupling is called an optron. Optrons are used to connect various components of electronic equipment, mainly in computers, meters, and automation equipment, where they provide electrical insulation of the components (as in a transformer). They are also used for contactless control of electric circuits, similar to a relay. The development of optrons began in the 1960’s.

In the emitter of an optron, the electric input signal is converted into a light signal and is transmitted through an optical channel to the photodetector (Figure 1), where it is converted back into an electrical signal. Semiconductor light-emitting diodes are usually used as light emitters, and the intermediate medium of the optical channel may be optical cement or glass, a fiber light guide, or air. Devices used as the photodetector include photodiodes, photoresistors, phototransistors, and photothyristors. The type of photodetector determines the output characteristics of the optron. The output signals of the optron are fed into amplifiers and photodetector converters, usually designed as integrated circuits. Such an assembly is called an optron integrated circuit.

The main properties of optrons are virtually complete electrical insulation of the input and output circuits, high electric strength (10⁴-10⁵ volts), unidirectional flow of information, the absence of back reaction from the photodetector to the emitter, a wide pass band (beginning from direct current), long service life, and small size and weight.