Optical multiplexer/demultiplexer

Claim 1

An optical wavelength multiplexer/demultiplexer comprising: an input channel waveguide provided on a substrate, the input channel waveguide being adapted for inputting a wavelength multiplexed signal light formed by multiplexing a plurality of signal lights having a predetermined wavelength spacing; an input slab waveguide for broadening the wavelength multiplexed signal light output from the input channel waveguide; an array waveguide diffraction grating having a plurality of channel waveguides, the plurality of channel waveguides having a waveguide length determined by the wavelength spacing and adapted for branching and propagating the wavelength multiplexed signal light output from the input slab waveguide to give a phase difference according to the waveguide length difference to the plurality of signal lights; an output slab waveguide for condensing the plurality of signal lights of the wavelength multiplexed signal light output from the plurality of channel waveguides in a plurality of predetermined condensing positions; and a plurality of output channel waveguides for propagating the plurality of signal lights branched and admitted from an incident end located in the plurality of predetermined condensing positions to output the propagated signal lights from an output terminal, a predetermined number of artificial waveguides having a predetermined core width being provided along the plurality of channel waveguides on both sides of the array waveguide diffraction grating.