Performance Limits of Inhomogeneous Fiber Optic Parametric Amplifiers Operated in Saturated Regime

Performance limits of saturated parametric amplifiers with very high nonlinear figure of merit were investigated. While such devices can be constructed using high confinement fiber, they also require localized phase matching control over hundreds of meters of interaction length. The limit on signal-induced pump depletion imposed by stochastic dispersion fluctuations in physical fibers is studied for a case of high-gain parametric amplifiers. We show that nanometer-scale fluctuations in fiber transverse geometry can lead to qualitatively different saturation characteristics in very efficient parametric devices. In contrast to a pump-undepleted parametric amplifier, an inhomogeneous parametric amplifier operated in saturation regime is found to possess truly nonreciprocal transfer characteristic.