Optical modulator, optical transmitter, and optical transceiver

An optical transmitter comprising:

• an optical modulator that modulates light that is guided in accordance with an electrical signal, wherein
• the optical modulator includes
• a substrate that includes a high refractive index waveguide;
• a first coupler that is arranged on the substrate and that splits signal light into two beams of light;
• a first waveguide that is arranged on the substrate and that is connected to one output of the first coupler;
• a second waveguide that is arranged on the substrate and that is connected to another output of the first coupler;
• a second coupler that is arranged on the substrate, that couples signal light coming from the first waveguide and signal light coming from the second waveguide, and that outputs the coupled signal light;
• and
• an electrode that applies an electrical signal to the first waveguide and the second waveguide,
• the first waveguide includes
• a first input-side arm waveguide that is connected to the first coupler;
• a first output-side arm waveguide that is connected to the second coupler;
• and
• a first folded waveguide that connects between the first input-side arm waveguide and the first output-side arm waveguide,
• the second waveguide includes
• a second input-side arm waveguide that is connected to the first coupler;
• a second output-side arm waveguide that is connected to the second coupler;
• and
• a second folded waveguide that connects between the second input-side arm waveguide and the second output-side arm waveguide,
• the first input-side arm waveguide, the second input-side arm waveguide, the first output-side arm waveguide, and the second output-side arm waveguide are waveguides that include a material with high EO characteristics as compared to the high refractive index waveguide, and
• at least a part of the first folded waveguide and the second folded waveguide is a waveguide that includes a material with a low refractive index as compared to the high refractive index waveguide.

An optical transceiver comprising:

• an optical modulator that modulates light that is guided in accordance with an electrical signal;
• an optical receiver that converts received signal light to an electrical signal;
• and
• a signal processor that generates an electrical signal to be output to the optical modulator and performs processing on an electrical signal that is obtained from the optical receiver, wherein
• the optical modulator includes
• a substrate that includes a high refractive index waveguide;
• a first coupler that is arranged on the substrate and that splits signal light into two beams of light;
• a first waveguide that is arranged on the substrate and that is connected to one output of the first coupler;
• a second waveguide that is arranged on the substrate and that is connected to another output of the first coupler;
• a second coupler that is arranged on the substrate, that couples signal light coming from the first waveguide and signal light coming from the second waveguide, and that outputs the coupled signal light;
• and
• an electrode that applies an electrical signal to the first waveguide and the second waveguide, and
• the first waveguide includes
• a first input-side arm waveguide that is connected to the first coupler;
• a first output-side arm waveguide that is connected to the second coupler;
• and
• a first folded waveguide that connects between the first input-side arm waveguide and the first output-side arm waveguide,
• the second waveguide includes
• a second input-side arm waveguide that is connected to the first coupler;
• a second output-side arm waveguide that is connected to the second coupler;
• and
• a second folded waveguide that connects between the second input-side arm waveguide and the second output-side arm waveguide,
• the first input-side arm waveguide, the second input-side arm waveguide, the first output-side arm waveguide, and the second output-side arm waveguide are waveguides that include a material with high EO characteristics as compared to the high refractive index waveguide, and
• at least a part of the first folded waveguide and the second folded waveguide is a waveguide that includes a material with a low refractive index as compared to the high refractive index waveguide.