Noise characteristics of fiber-based optical phase conjugators

This paper presents a theoretical and experimental analysis of the noise characteristics of a fiber based optical phase conjugator. The results are used to derive an expression for the noise figure (NF) of the device. The lowest measured NF is 18 dB, at -15 dB net conversion efficiency. This NF was limited by stimulated Brillouin scattering (SBS) and amplified spontaneous emission from an optical amplifier. Using the experimental parameters, the theoretical values agree well with the measurements, and predicts in our particular case a minimum NF of 10 dB at high conversion efficiencies. Furthermore, we investigate the influence of optical amplifiers before and after the conjugator, and, with all excess noise eliminated, we predict the quantum limit of 3 dB at efficiencies much greater than 100%.