Device and method for comparing optical signals

摘要

An optical comparator for comparing, bit by bit, corresponding bits of two optical digital signals which are identical in the number of constituent optical bit signals, includes an optical waveguide layer made of an acousto-optical material. A surface acoustic wave generator generates a surface acoustic wave propagating on the waveguide layer, and a photocoupler directs the constituent bit signals to be of the two optical digital signals incident on the waveguide layer so as to satisfy the Bragg diffraction condition with respect to the surface acoustic wave propagating on the waveguide layer. A photosensor detects diffracted light and/or undiffracted light which has passed through a surface acoustic wave interaction region. The position of the generator and/or the surface acoustic wave generating timing is so determined that initiation or cessation of the interaction of the surface acoustic wave with a bit of one of the optical digital signals is simultaneous with initiation or cessation of the wave interaction with a corresponding bit of the other optical bit signal.