Patent ID: 7365904

Claim:
An optical wavelength converter, comprising: a first branch passage; a second branch passage, wherein the first branch passage and the second branch passage form part of a Mach-Zehnder interferometer, both of the first branch passage and the second branch passage receive direct current light at a fixed wavelength, and one of the first branch passage and the second branch passage receives input signal light having a signal wavelength; first and second wavelength converting semiconductor optical amplifiers inserted into the first branch passage and the second branch passage, respectively; and a signal amplifying semiconductor optical amplifier for amplifying the input signal light, and coupled with a port through which the input signal light is input to the one of the first branch passage and the second branch passage, wherein each of the first and second wavelength converting semiconductor optical amplifiers and the signal amplifying semiconductor optical amplifier includes a respective active layer, and the active layers of the first and second wavelength converting semiconductor optical amplifiers are different from the active layer of the signal amplifying semiconductor optical amplifier so that differential gain of the signal amplifying semiconductor optical amplifier at the signal wavelength of the input signal light is less than differential gain of the first and second wavelength converting semiconductor optical amplifiers at the fixed wavelength of the direct current light.