LIGHT 90-DEGREE HYBRID CIRCUIT

摘要

Disclosed is a light 90-degree hybrid circuit provided with a monitoring function for IQ phase difference. The light 90-degree hybrid circuit is provided with a first demultiplexing optical coupler having two or more first input ports and two or more first output ports, a second demultiplexing optical coupler having two or more second input ports and two or more second output ports, two first arm waveguides connected to the first output ports, two second arm waveguides connected to the second output ports, a 90-degree phase shift section provided to one of the four arm waveguides, a first optical coupler connected to one of the first arm waveguides and one of the second arm waveguides, a second optical coupler connected to the other of the first arm waveguides and the other of the second arm waveguides, a first optical waveguide for connecting an optical splitter and the other first input port, and a second optical waveguide for connecting the optical splitter and the other second input port. The optical length of the first optical waveguide is different from that of the second optical waveguide.