| 摘要 |
The present application provides an asymmetric Y branch optical waveguide capable of obtaining an asymmetric branching ratio stably with a low radiation loss, and a lightwave circuit and an optical transmission system both using the asymmetric Y branch optical waveguide. The asymmetric Y branch optical waveguide according to the present application has a waveguide (I) for input, two waveguides (III) for output, and a multi-mode waveguide (II) disposed between the waveguides (I) and (II). The present Y branch optical waveguide is constructed in such a manner that the width of the multi-mode waveguide, extending in the direction intersecting with an optical axis changes discontinuously at a portion where the input waveguide and the multi-mode waveguide are connected to each other, and the multi-mode waveguide is asymmetric with respect to a center line extending in the direction of the optical axis to allow optical peaks to respectively appear in each individuals of the two output waveguides. Thus, a difference occurs between peak's heights in each light-intensity distribution having two peaks, which appears due to mode interference, so that the asymmetry of a branching ratio can be implemented.
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