| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical 90° hybrid circuit capable of suppressing deterioration of reception characteristics depending on wavelength of light to be input.SOLUTION: An optical 90° hybrid circuit includes: a 1/2 wavelength plate pair 10 on which signal light 6 is made incident; a 1/4 wavelength plate 3 on which the signal light 6 emitted from the 1/2 wavelength plate pair 10 is made incident; a half mirror 4 on which both of the signal light 6 emitted from the 1/4 wavelength plate 3 and local light 7 are made incident; and a polarization separator 5 on which the signal light 6 and the local light 7 transmitted or reflected on the half mirror 4 are made incident, and separately emits the light as a plurality of pieces of output light 8, the 1/2 wavelength pair 10 has a first 1/2 wavelength plate 1 and a second 1/2 wavelength plate 2, a first optical axis of the first 1/2 wavelength plate is arranged at an angle of (45+p1×90)/2° (p is an integer) to a second optical axis of the second 1/2 wavelength plate 2. |
