Degenerate modes multiplexer/demultiplexer using Mach-Zehnder interferometer with image inversion

A novel degenerate mode multiplexer/demultiplexer using Mach-Zehnder interferometer with an image inversion function is proposed and developed. Low-loss multiplexing/demultiplexing operation of degenerate modes of LP11ab, LP21ab and LP31ab is experimentally demonstrated respectively.