| 摘要 |
An arrayed waveguide grating type optical multiplexer/demultiplexer in which the 1 dB band width is large, the ripple is small, and the degradation of the adjacent crosstalk can be controlled. A waveguide forming portion is formed on a substrate. The waveguide forming portion includes an optical input waveguides, a first slab waveguide, an arrayed waveguide including a plurality of channel waveguides arranged side by side and which have different lengths with the differences preset, a second slab waveguide, and a plurality of optical output waveguides arranged side by side, all of the components being connected in the order stated. A single mode straight waveguide narrower than the optical input waveguides is provided at the output end of at least one or more optical input waveguides. A multi-mode trapezoidal waveguide whose width increases toward the arrayed waveguide is provided at the output end of the straight waveguide. An upper base of the trapezoidal waveguide is longer than the diameter of the optical input waveguide.
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