Patent ID: 7233742
Filing Date: 2007-06-19
Classification: H04B

Abstract:
1. An optical communication system comprising: a transmitting station; an optical transmission line for transmitting a wavelength division multiplexed (WDM) optical signal sent from said transmitting station; a receiving station for receiving said optical signal outputted from said optical transmission line; a repeater station provided in said optical transmission line between said transmitting station and said receiving station; a first pump light source, located in one of said transmitting station, said receiving station, and said repeater station, supplying pump light at a first wavelength to said optical transmission line; a second pump light source, located in a different one of said transmitting station, said receiving station and said repeater station, supplying pump light at second wavelength, different from the first wavelength, to said optical transmission line, wherein the pump light at the first wavelength and the pump light at the second wavelength cause Raman amplification of said optical signal to occur in different spans of said optical transmission line, and thereby cause the optical signal to be amplified by a combined Raman amplification as the optical signal travels through the different spans, the first and second wavelengths being selected to reduce gain tilt of the combined Raman amplification and thereby provide a substantially flat gain over wavelengths of the optical signal; and a controller centrally controlling settings of the first and second wavelengths through communication lines to the first and second pump light sources, to reduce the gain tilt, wherein the controller controls the setting of the first and second wavelengths in a repeating, sequential order.