200-GHz FSR periodic multi/demultiplexer with flattened transmission and rejection band by using a Mach-Zehnder interferometer with a ring resonator

Abstract
A periodic multi/demultiplexer that has a square spectrum response with a 200-GHz free spectrum range was fabricated using a modified Mach-Zehnder interferometer with MMI couplers, a delay line, and a ring resonator. A large enhancement of the FSR is obtained by using a deep ridge waveguide. The transmission bandwidths of 1 dB down and -15-dB rejection are about 75 GHz and over 50 GHz, respectively.