An arrayed waveguid grating 101 is shown, which comprises at least one input waveguide 103, a plurality of output waveguides 104, at least one wavelength compensation output waveguide 105 disposed adjacent to the output waveguide 104, a channel waveguide array 107, an input side slab-waveguide 108, and an output side slab-waveguide 109. The wavelength compensation output waveguide 105 has a tapering connecting portion connected to the output side slab-waveguide 105. Thus, the outputted light has a sharp spectrum, thus permitting ready wavelength compensation.
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