Bandpass filter demonstration using all-pass filter decomposition and ring resonators

Elliptic filters are optimum in the sense of providing the most ideal bandpass response, i.e. the most square response, for a given passband and stopband ripple and with the fewest number of stages; consequently, they are very attractive for (de)multiplexing and add/drop applications in WDM systems. Recently, a new optical architecture based on all-pass filter decomposition was described in theory which can exactly realize elliptic filters as well as other designs such as the Butterworth and Chebyshev. The first experimental demonstration of this architecture is reported using planar waveguide ring resonators