Polarization independence and phase-sensitive parametric amplification

Abstract

We investigate the possibility of obtaining phase-sensitive amplification (PSA) in a fiber-optic parametric amplifier (OPA), with gain independent of the state of polarization of the input signal, i.e., polarization-independent amplification. We consider both a single OPA with two orthogonal pumps and a polarization-diversity scheme. In either case, PSA with maximum gain is possible, provided that the signal and idler are in suitably matched polarization states; this condition is naturally satisfied by the output fields of an upstream polarization-insensitive amplifier of the same type. Two polarization-multiplexed signals can then be simultaneously amplified in the PSA. The low noise figure can also be obtained with these types of PSA. However, in general, this favorable situation is not maintained if the signal and idler states of polarization drift together due to birefringence fluctuations in a transmission fiber preceding the PSA.