Patent ID: 8363311

Claim:
An optical amplifier for amplifying an optical signal having a signal wavelength and a signal power, the optical amplifier having an amplifier gain, the optical amplifier comprising: an optical waveguide doped with a rare earth element; an optical pump for pumping the optical waveguide with a pump light, whereby an optical gain at the signal wavelength is created in the optical waveguide, wherein the optical gain is dependent on the signal power; and an optical anti-pump for pumping the optical waveguide with an anti-pump light at an anti-pump wavelength longer than the signal wavelength, so as to create a dependence of an optical loss in the optical waveguide on the signal power, substantially compensating the dependence of the optical gain on the signal power and thereby lessening a variation of the amplifier gain with the signal power, wherein the optical waveguide has first and second segments optically coupled to be pumped at different ratios of optical powers of the pump and the anti-pump light.