Patent ID: 7245422

Claim:
A Raman optical amplifier comprising: an amplification medium inputted a first light, that has a first wavelength and is polarized in a first plane of polarization, and a second light, that has a second wavelength different from the first wavelength and is polarized in a second plane of polarization substantially orthogonal to the first plane of polarization; and a pumping device inputting, to said amplification medium, a first pump light, for amplifying the first light and that is polarized in a third plane of polarization which coincides with the first plane of polarization, and a second pump light, for amplifying the second light and that is polarized in a fourth plane of polarization which coincides with the second plane of polarization, wherein said amplification medium is a polarization maintaining fiber maintaining states of polarization of the first light, the second light, the first pump light and the second pump light.