Patent ID: 6928214

Claim:
An optical communication system comprising: an optical transmission means for sending out light signals of different wavelengths as parallel signals; a multiplexer constituted by an array waveguide grating for wavelength multiplexing/demultiplexing each of the different wavelength light signals sent out from the optical transmission means; an optical transmission line, to which the wavelength divided and multiplexed light signals outputted from the multiplexer are sent; a node provided in the optical transmission line and having an array waveguide grating; a demultiplexer constituted by an array waveguide array for receiving input light signal set along the optical transmission line via the node; and an optical receiving means for receiving the demultiplexed different wavelength light signals from the demultiplexer; wherein the demultiplexer includes a predetermined substrate, a first and a second channel waveguide for light wave transfer on the substrate, a channel waveguide array having a plurality of component waveguides having lengths progressively increasing with a predetermined difference between adjacent ones of the waveguides on the substrate, a first slab waveguide for connecting the ends of the first channel waveguides and one end of the channel waveguide array via a waveguide part having a first shape on the substrate, and a second slab waveguide for connecting one end of the second channel waveguides and the other end of the channel waveguide array via a waveguide part having a second shape on the substrate, and at least the open part of each of the first channel waveguides on the side of the first slab waveguide or the open part of each of the second channel waveguides on the side of the second slab waveguide is flaring in an exponential function shape toward the channel waveguide array.