Gain saturation in a Raman-assisted fiber optical parametric amplifier

We investigate the gain saturation characteristics in a backward-pumped Raman-assisted fiber optical parametric amplifier (FOPA). It is experimentally observed that the onset of saturation occurs at a higher input power as compared to the case of a conventional FOPA with the same unsaturated gain. The output power under strong saturation is also enhanced. Simulations are performed on the power profile of the parametric pump to explain the distinct saturation behaviors. The monotonic increase of the parametric pump power in the Raman-assisted FOPA results in highly efficient power transfer to the signal while it suppresses the signal conversion to high-order idlers in the saturation regime.