Dynamic properties of double-pass discrete Raman amplifier with FBG-based all-optical gain clamping techniques

The authors propose and implement a discrete fiber Raman amplifier configured in double-pass scheme together with fiber Bragg grating (FBG)-based all-optical feedback. The double-pass amplifiers achieve more than a 30-dB net gain with affordable pump power and guarantee a large margin for gain clamping. The all-optical gain clamping is provided by the lasing wavelength inside the cavity caused by the high reflectivity FBG and wide-band reflector. A stable gain is obtained for large input signal dynamic range of 30 dB. The gain variation is kept below 0.17 dB and the noise figure is flattened at the same time. Also, the authors investigate the Raman gain and noise figure as a function of signal wavelength with the proposed gain clamping technique.