An optical heterodyne mixer providing image-frequency rejection.

This paper describes an optical heterodyne mixer which detects a desired signal at frequency f(L.O.+-)f(IF) while rejecting interference from any signal at the image frequency f(L.O. -+)f(IF). Implementation of the mixer is relatively simple. Its performance is insensitive to fluctuations in the optical dimensions of the circuit. This mixer is particularly attractive for Local Area Network applications and communication systems using Wavelength Division Multiplex techniques.