Role of Absorption on the Generation of Quantum-Correlated Photon Pairs Through FWM

The impact of fiber absorption on the generation rate of quantum-correlated photon pairs through spontaneous four-wave mixing in optical fibers is studied theoretically. We quantify the impact of the loss through the analysis of the Cauchy-Schwarz correlation parameter and the Clauser, Horne, Shimony, and Holt inequality. Results show that fiber loss can improve the quantum-correlation between the photon pairs. This is a consequence of the decrease of the individual signal and idler photon-fluxes, which reduces the rate of uncorrelated photons generated through Raman scattering inside the optical fiber. Findings show that a high degree of polarization entanglement is obtained when the ratio of signal to idler photon-fluxes lies between 0.5 and 0.8, in a regime with high losses on the signal wave.