Design of a spectrum-periodized polymer optical filter using arc-type Mach–Zehnder interferometer and Nth order phase-generating couplers

Abstract

We proposed a kind of polymer arc-type Mach–Zehnder interferometer (MZI) optical filter by employing two parallel cascaded Nth-order phase-generating couplers (PGCs). To realize periodic spectrum response with low insertion loss, a nonlinear least square method was investigated for optimizing PGC structure to satisfy periodic phase compensation (PPC) and insertion loss compensation (ILC) conditions. With the needed wavelength period of 24 nm, design and simulation on five Nth-order PGCs-based filters were performed as N changes from 0 to 4. When N=3, the optimized filter exhibits the most favorable uniform periodic response with the maximum period shift less than 0.3 nm, which is about 1/10 times of that of the traditional filter when N=0, and the insertion loss at the central wavelength of each channel is 1.39–9.98 dB. The PGC’s order N should be properly selected for low optical loss, uniform wavelength period, and feasible optimization complexity. The proposed technique can also be used to design such PGCs-based arc-type MZI filters with any other uniform wavelength period by altering the radius-difference between two arc-type MZI waveguides for CWDM networks.