Low-Loss and Fabrication-Tolerant Si Four-Wavelength Multiplexer using Higher-Order Mode for 100/400GbE

A Si four-wavelength multiplexer for 100/400GbE composed of (a)symmetric directional couplers and a rib-waveguide mode-converter is experimentally demonstrated. Proposed device is fabrication-tolerant due to the removal of 1600-GHz filter used in conventional two-stage Mach-Zehnder multiplexers.