Patent ID: 7197247

Claim:
A WDM optical communication system, said system comprising an optical signal input, an optical signal output, an optical fiber path having at least one Raman amplifier and connecting said input and output, said Raman amplifier receiving a plurality of pump signals whereby an optical signal at said input is amplified by means of Raman amplification during passage through said optical fiber path, wherein said pump signals include a first pump signal having a first pump wavelength in a first part of a pump wavelength band, a second pump signal having a pump wavelength in a continuous second part of said pump wavelength band, and a third pump signal having a third pump wavelength in said second part of said pump wavelength band, wherein the polarization of said first pump signal is different from the polarizations of said second and third pump signals and bears the same predetermined relationship to the polarizations of each of said second and third pump signals.