Phase noise generation in an amplitude limiter using saturation of a fiber-optic parametric amplifier

Generation of phase noise in an amplitude limiter using saturation of a fiber-optic parametric amplifier is analyzed. The analysis is based on the coupled differential equations for the amplitudes and phases of pump, signal, and idler involved in the four-wave mixing interaction. The equations are linearized about small fluctuations at operation points and are solved, which results in relations between the input and output phase and amplitude noise. These relations are used in deriving expressions of amplitude signal-to-noise ratio (SNR) and variance of phase noise of the output signal in terms of SNRs of input signal and pump. It is shown that optimum pump power exists for minimum output phase noise in the output signal.