Silicon-on-insulator eight-channel optical multiplexer based on a cascade of asymmetric Mach-Zehnder interferometers

A monolithically integrated eight-channel optical multiplexer (Mux) with a $400\mathrm{GHz}$ channel spacing $\sim 1550\mathrm{nm}$ is presented based on a silicon-on-insulator rib waveguide and an asymmetric Mach–Zehnder interferometer. All channels were optimized independently with integrated heaters. The fully tuned Mux shows an adjacent channel isolation of $\sim 13\mathrm{dB}$, an excess loss of $\sim 2.6\mathrm{dB}$, and a channel uniformity of $\sim 1.5\mathrm{dB}$ over a $25\mathrm{nm}$ wavelength span. In addition, the phase tuning efficiency for different interlevel dielectric layer thicknesses and thermal crosstalk were investigated.