Patent ID: 8483525

Claim:
An optical wavelength multiplexing/demultiplexing circuit comprising: an arrayed-waveguide grating including arrayed waveguides and a first slab waveguide and a second slab waveguide that are respectively connected to the ends of the arrayed waveguides; a first input and output waveguide optically connected to the first slab waveguide via an interference circuit; and a second input and output waveguide connected to the second slab waveguide, wherein the interference circuit includes: a first arm waveguide, a second arm waveguide extended adjacent to the first arm waveguide and having a different length, an optical mode converter which is connected between one ends of the first arm waveguide and the second arm waveguide and an interface of the first slab waveguide, the optical mode converter couples fundamental mode that is received from the first arm waveguide with first mode, and forms an optical field distribution representing a change in a peak position on an interface with the first slab waveguide according to a wavelength, and an optical splitter connected to the other ends of the first arm waveguide and the second arm waveguide, wherein an optical frequency spacing for the interference circuit matches an optical frequency channel spacing for the arrayed-waveguide grating, and a splitting ratio of the optical splitter changes with a spacing that is identical to or half the optical frequency spacing for the interference circuit, and takes a minimum value in the vicinity of an optical center frequency of each channel in the arrayed-waveguide grating.