Method and apparatus for optical mode division multiplexing and demultiplexing

An apparatus to transfer a signal from a first mode of a first waveguide to a second mode of second waveguide, the apparatus comprising first and second waveguides, wherein the second waveguide is aligned substantially along said first waveguide, an initial portion of said second waveguide located at an initial distance from the first waveguide so as not to affect any mode in the first waveguide, and wherein the distance between the second waveguide and the first waveguide gradually decreases to a mode interaction region, thereby enabling adiabatic transfer of a signal carried by a first mode of said first waveguide to a second mode of said second waveguide having the same direction of propagation as said first mode, without affecting any other signal carried by any other mode of said first and second waveguides or any counter-propagating signal, wherein said adiabatic transfer of said signal is irrespective of operation wavelength of the signal.