“…Since each mode is an independent channel thus potentially makes a myriad of single channel capacity for optical communications systems and optical interconnects when it combines with the wavelength division multiplexing (WDM) technique 6 , 7 . Various kinds of MDM systems have been proposed, for example, mode demultiplexer 8 , 9 , mode converter 10 , 11 , waveguide crossing 12 , 13 , mode selective switch 14 , 15 , mode add-drop multiplexer 16 , 17 , and mode router 18 .…”