Patent ID: 6842560

Claim:
An optical multiplexing circuit to which a plurality of optical signals are input and which outputs a multiplexed beam subjected to wavelength division multiplexing, comprising: a plurality of input transmission channel waveguides to each of which a corresponding one of a plurality of optical signals is input; plural pairs of input monitoring channel waveguides into which a beam is introduced in a direction opposite to that for the input transmission channel waveguides and which output demultiplexed beams, each of the pairs including a first input monitoring channel waveguide and a second input monitoring channel waveguide; an input slab waveguide having a first facet, wherein the first facet connected to said plurality of input transmission channel waveguides and said plural pairs of input monitoring channel waveguides; at least one output transmission channel waveguide to which the multiplexed beam is guided, the multiplexed beam being obtained by multiplexing said plurality of optical signals transmitted from said plurality of input transmission channel waveguides; at least one output monitoring channel waveguide into which a beam is introduced in a direction opposite to that for the output transmission channel waveguides and which transmits said demultiplexed beams to said plural pairs of input monitoring channel waveguides; an output slab waveguide having a fourth facet, wherein the fourth facet connected to said at least one output transmission channel waveguide and said at least one output monitoring channel waveguides; and an arrayed waveguide comprising a plurality of optical waveguides having different optical path lengths, wherein the arrayed waveguide is connected to a second facet which is located opposite said first facet of said input slab waveguide, and is connected to a third facet which is located opposite said fourth facet of said output slab waveguide, wherein when said multiplexed beam is introduced into said fourth facet of said output slab waveguide through said output monitoring channel waveguide, the multiplexed light passes through the output slab waveguide and is demultiplexed by said input slab waveguide, and the demultiplexed beams are guided to the first facet and are output to said each pair of input monitoring channel waveguides having a corresponding wavelength.