Optical isolator

In telecommunication, an optical isolator is a device that uses a short optical transmission path to accomplish electrical isolation between elements of a circuit.

Note 1: The optical path may be air or a dielectric waveguide.

Note 2: The transmitting and receiving elements of an optical isolator may be contained within a single compact module, for mounting, e.g., on a circuit board. Synonym optoisolator.

Source: from Federal Standard 1037C