Optical Wavelength Interleaver using Cross-coupled and Direct-Coupled All-Pass Filters

This work presents the experimental realization of an integrated optical wavelength (de)interleaver using a non-conventional cross-coupled all-pass filter, inspired by the theoretical framework proposed by Dingel et al. [1], for wavelength (de)interleaving in wavelength-division multiplexed (WDM) optical communications. By integrating a direct-coupled all-pass filter (D-APF; conventional geometry with a ring resonator and a bus waveguide) and a cross-coupled filter (C-APF; non-conventional all-pass filter geometry) into a Mach-Zehnder interferometer (MZI) geometry, the device exhibits periodic pass and stop bands in the spectral domain. Reversible output port switching can also be obtained via thermo-optic phase modulation in one arm of the MZI (Fig. 1(a)).