Patent ID: 7027214

Claim:
An optical transmission system comprising at least one transmitter, at least one transmission line including at least one optical fiber amplifier, and at least one receiver communicably linked to the transmitter via the transmission line, the optical fiber amplifier being designed to show a flat characteristic of output power versus wavelength, wherein the optical fiber amplifier is designed to show the flat output characteristic in response to a flat characteristic of a first input power level versus wavelength, the transmission system further comprising at least one coupler and at least one Raman amplifier coupled to the transmission line via the coupler, the Raman amplifier comprising a plurality of Raman pumps and having a Raman gain that is tilted in a direction opposite to a tilt of the optical fiber amplifier that would occur in response to a flat characteristic of a second input power level versus wavelength such that the opposite tilt directions of the Raman amplifier and the optical fiber amplifier compensate each other and a noise figure characteristic achieved with the Raman gain rises with increasing wavelengths.