Patent ID: 8630517

Claim:
An optical multiplexer/demultiplexer having a core embedded in a clad, the core comprising: an input optical waveguide for input of mixed light including light of a first wavelength and light of a second wavelength; an input slab optical waveguide connected to the input optical waveguide; a waveguide array comprising a plurality of channel optical waveguides connected to the input slab optical waveguide; an output slab optical waveguide connected to the waveguide array; a first multimode coupler configured as a multimode optical waveguide connected to the output slab optical waveguide; a second multimode coupler configured as a multimode optical waveguide connected to the output slab optical waveguide; a first output optical waveguide connected to the first multimode coupler for output of the light of the first wavelength; and a second output optical waveguide connected to the second multimode coupler for output of the light of the second wavelength; wherein the core and the clad have refractive indexes mutually differing by at least 40%; the first multimode coupler has dimensions such that for both TE and TM polarized waves, a phase difference between the light of the first wavelength propagating in a fundamental mode and the light of the first wavelength propagating in a second-order mode through the first multimode coupler, from a point of connection with the output slab optical waveguide to a point of connection with the first output optical waveguide, changes by (2i+1)π radians, where i is a non-negative integer; and, the second multimode coupler has dimensions such that for both TE and TM polarized waves, a phase difference between the light of the second wavelength propagating in the fundamental mode and the light of the second wavelength propagating in the second-order mode through the second multimode coupler, from a point of connection with the output slab optical waveguide to a point of connection with the second output optical waveguide, changes by (2j+1)π radians, where j is a non-negative integer.