Fabrication of coherent optical transversal filter consisting of MMI splitter/combiner and thermo-optic amplitude and phase controllers

摘要

The fabrication of an integrated-optic coherent transversal filter which is capable of synthesising almost arbitrary filter characteristics is reported. The transversal filter consists of a multimode interference (MMI) splitter for 1/spl times/N signal splitting, delay arms with fixed path length difference, thermo-optic switches and phase shifters for arbitrarily weighting the signal and MMI N/spl times/1 combiner to combine N tapped signals. Sine-type and Gaussian-type spectral filter responses have been successfully realised showing good agreement with theoretical characteristics.