Nonlinear Interactions in Optical Amplifiers for Multi-Frequency Lightwave Systems

Nonlinear interactions that occur in an optical amplifier, between the carrier density and multiple optical signals, are described using a small- signal analysis. In multi-frequency lightwave systems with channel separations less than 1 GHz, the ratio of the signal power to the total intermodulation interference may be less than 25 dB, for total output intensities 10 dB below the amplifier saturation intensity.