Noise in Orthogonally-Pumped Fiber-Optical Parametric Amplifiers

The noise figure of a fiber-optical parametric amplifier, driven by pumps with orthogonal polarizations, is quantified experimentally. It is shown that this amplifier has a signal-polarization- dependent gain, with a corresponding polarization-dependent noise figure. The polarization dependence of the noise figure is particularly large when higher input-signal powers are amplified, in which case pump-induced noise dominates. At lower input-signal powers, the noise figure is less dependent on the input polarization, but increases closer to the lower-frequency pump.