CASCADED COUPLER MACH-ZEHNDER CHANNEL DROPPING FILTERS FOR WAVELENGTH-DIVISION-MULTIPLEXED OPTICAL-SYSTEMS

We describe the design and characteristics of cascaded coupler Mach-Ze hnder (CMZ) channel adding/dropping filters that select every nth chan nel (n = 2,3,4, ...) from the wavelength-division-multiplexed (WDM) op tical signal. Using the truncated binomial coupling weight distributio n, which appears to be optimal, such filters achieve low (< -30 dB) si delobe levels and good finesse with just a modest number of stages. We also show that the number of filter stages grows only linearly with t he required filter finesse and thus the number of selectable channels. Such WDM filters can be conveniently implemented using the silicon or InP integrated optical technology.