Silica Waveguide Four-Mode Multiplexer Based on Cascaded Directional Couplers

Mode multiplexers/demultiplexers (MUX/deMUX) are key components in mode division multiplexing. A silica waveguide mode MUX consisting of four cascaded directional couplers is experimentally demonstrated. The beam propagation method is used in the device design and optimization. Thermal oxidation, plasma-enhanced chemical vapor deposition, and ultraviolet photolithography are adopted in the silica waveguide mode MUX fabrication. The measurement results prove that the input E00 mode can be selectively converted to E10 mode, E20 mode, and E30 mode. Within the wavelength range of 1500 to 1620 nm, the insertion loss is less than 12.2 dB. The proposed mode MUX has good potential in on-chip MDM applications.