Optical modulator

摘要

In order to provide an optical modulator capable of suppressing generation of mode mismatching light in the Y-multiplexer in the MZ-type waveguide or mixing of the mode mismatching light with the radiation-mode light or the output light, and separately extracting output light and radiation-mode light, there is provided an optical modulator having a Mach-Zehnder type waveguide on a surface of a dielectric substrate, wherein a waveguide after multiplexing in a Y-multiplexer in an output side of the Mach-Zehnder type waveguide is a multiple mode waveguide 2, a subsidiary output waveguide as a high-order mode waveguide 2 is connected to a portion where the multiple mode waveguide is changed to a main output waveguide 3 as a single mode waveguide, and the multiple mode waveguide 2 has a length equal to or longer than 150 μm.

主权项

1. An optical modulator having a Mach-Zehnder type waveguide on a surface of a dielectric substrate, wherein
a waveguide, after multiplexing in a Y-multiplexer in an output side of the Mach-Zehnder type waveguide, includes only a multiple mode waveguide in its coupling portion, two subsidiary output waveguides that are high-order mode waveguides and that guide radiation-mode light are connected to a portion where the multiple mode waveguide is changed to a single mode waveguide that is a main output waveguide guiding signal output light, the two subsidiary output waveguides are arranged axisymmetrically with respect to the main output waveguide by interposing the main output waveguide therebetween, the multiple mode waveguide has a length equal to or longer than 150 μm, a distance between outer edges of two branching waveguides coupled in the Y-multiplexer is equal to a width (W2) of the multiple mode waveguide at a connection point of the branching waveguides with the multiple mode waveguide, and a distance between outer edges of the two subsidiary output waveguides is equal to a width (W4) of the multiple mode waveguide at a connection point of the subsidiary output waveguides with the multiple mode waveguide.