Silicon-Photonic Dense 8-Channel Multiplexer Using Auto-Regressive Moving-Average Filters

We propose and demonstrate an integrated 8-channel dense wavelength division multiplexer in silicon-on-insulator platform. The device layout comprises of 7 stages in a tree topology. Each stage is based on an unbalanced Mach-Zehnder interferometer with a nested ring resonator. The transfer function of each stage is that of an auto-regressive moving-average filter, characterized by a uniform passband, strong out-of-band rejection and sharp spectral transitions. The passband of each channel is extremely narrow: only 0.135 nm (16 GHz), and the worst-case crosstalk among channels is -22 dB. Individual phase delays within the device are trimmed through selective photo-removal of an upper cladding layer of photo-sensitive chalcogenide glass. The devices are suitable for integrated-photonic processing of radio-over-fiber and mm-wave communication.