COHERENT OPTICAL TRANSVERSAL FILTER USING SILICA-BASED WAVE-GUIDES 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 are developed for stable and high-speed operation. Experimental results demonstrate the operating capabilities of the filters for high-speed signal processing, and the operating bandwidth is experimentally estimated. Degradation of the frequency characteristics due to both deviation of fiber fabricating parameters and errors in setting tap-coefficients is theoretically estimated.