Coherent optical transversal filter using silica-based waveguides for high-speed signal processing

A coherent optical transversal filter with a tapped delay-line structure is described. Utilizing phase information this filter can express arbitrary tap coefficients (including general complex numbers) by coherently combining tapped signals. Experimental filters using silica-based single-mode optical waveguides, monolithically integrated on silicon substrates were developed for stable and high-speed operation. Experimental results demonstrate the operating capabilities of the filters for high-speed signal processing. The operating bandwidth was experimentally estimated. Degradation of the frequency characteristics due to both deviation of fiber fabricating parameters and errors in setting tap-coefficients has been estimated theoretically.>