Patent ID: 7262905

Claim:
An optical amplifier characterized by comprising: a symmetrical Mach-Zehnder interference circuit formed on a substrate and having an amplification function having a first coupler on an input side and a second coupler on an output side; an input waveguide coupled to an input side of a first arm of said symmetrical Mach-Zehnder interference circuit via said first coupler; an output side oscillation light waveguide coupled to an output side of the first arm of said symmetrical Mach-Zehnder interference circuit via said second coupler; an input side oscillation light waveguide coupled to an input side of a second arm of said symmetrical Mach-Zehnder interference circuit via said first coupler on the input side of said symmetrical Mach-Zehnder interference circuit; an output waveguide coupled to an output side of the second arm of said symmetrical Mach-Zehnder interference circuit via said second coupler on the output side of said symmetrical Mach-Zehnder interference circuit; a semiconductor optical amplifier coupled to said output side oscillation light waveguide; a first reflecting mirrors formed at one end on an input side of said input side oscillation light waveguide; and, a second reflecting mirror formed at one end on an output side of said output side oscillation light waveguide.