Pump Noise Coupling in Parametric Amplifiers

A simple theory for predicting the effects of pump noise on the performance of parametric amplifiers has been developed and verified. It is shown that AM noise on the pump injects both FM and AM noise on the signal magnified by approximately the amplifier gain. It is also shown that FM noise on the pump can yield both FM and AM noise on the amplified signal : in this case the coupling coefficient for simple amplifiers is shown to be a function of the idler bandwidth. Analytic expressions for the maximum coupling factors are quoted for the case of a simple amplifier. Experiments on two different amplifiers are described which both support the theoretical predictions.