Multi-channel wavelength-routing switch using acousto-optic polarization

Abstract

Acousto-optic polarization converters can be used as the primary optical components in a multi-channel wavelength-routing switch (101). Switching efficiency is decreased and the polarization converted wavelength channels are shifted towards each other, however, when closely neighboring channels are selected simultaneously. This degradation has serious consequences for many applications of the acousto-optic polarization converter. By applying counterpropagating acoustic waves from opposite ends of a converter (400) and using an acoustic absorber (417) to separate the left and right sides of the converter at a defined coupler crossover length, L.sub.x, this deleterious degradation is substantially reduced. Specifically, by separating the primary acousto-optic interaction regions for the right propagating acoustic waves and the optical signal which polarization is to be converted, from the primary acousto-optic interaction regions for the left propagating acoustic waves and that same optical signal, so that adjacent closely neighboring wavelength channels are converted in opposite sides of the converter, channel shifting is reduced. Further, by using a partial absorber at the crossover length, L.sub.x, to separate the left and right converter sides, a flattened passband is created which decreases the consequences of any residual channel shifting.