Experimental validation of double-pass amplification in discrete Raman amplifier

This report is presented to validate the double-pass amplification characteristics in discrete Raman. The double-pass discrete Raman amplifier (DRA) based on dispersion compensating fiber (DCF) and high reflection fiber Bragg grating (FBG) at pump wavelength is constructed with the pump light at 1435 nm launched in counter-directional to the incoming input signal. The double-pass direction of the signal is achieved through a fiber loop mirror constructed by a circulator. From the experimental result, we show that this design is mostly suitable for small signal region. The small signal input regime from -40 dBm up to -10 dBm will benefit from the high-gain and low-noise characteristics of double-pass design. It is observed that, the maximum of 22 dB gain is achieved with the noise figure maintained at less than 5 dB.