Patent ID: 7106499

Claim:
An optical communication system, a Raman amplification medium; a pumping portion for injecting pump light giving the gain to signal light depending on the intensity of the pump light by induced Raman effect in said Raman amplification medium; a monitor portion for measuring only an input power of the signal light; and a control portion for controlling said pumping portion according a result of measurement by said monitor portion, said pumping portion including: a forward pumping portion provided in a transmitter, for injecting at least one forward pump light propagating in the same direction as the signal light in said Raman amplification medium; and a backward pumping portion provided in a receiver, for injecting at least one backward pump light propagating in the opposite direction to the signal light in said Raman amplification medium, said control portion including means for controlling ratio of the gain of the signal light by the backward pump light to the gain of the forward pump light based on the measurement performed by the monitor portion. said Raman amplification medium including an optical fiber as an optical transmission path connecting between said transmitter and said receiver, wherein sign of dispersion value of said optical fiber is negative in at least a portion of a wavelength range of the signal light and an absolute value thereof is 20 ps/nm/km or more in at least a portion of the wavelength range of the signal light.