The Raman-assisted wavelength-shift-free optical phase conjugator based on Sagnac fiber loop

We propose the use of distributed Raman amplification (DRA) for improving the conversion efficiency of the wavelength-shift-free Sagnac-based optical phase conjugator (OPC). Comparing to the wavelength-shift-free OPC with the absence of DRA, we achieve the improvement of the conversion efficiency over 6 dB, while the conjugated signal quality remains almost unchange. Nevertheless, the input signal power and the DRA pump powers are found to be the important parameters that should be carefully determined for trading off the increase in conversion efficiency for the acceptable conjugated signal quality.