Influence of Pump-to-Signal RIN Transfer on Noise Figure in Silicon Raman Amplifiers

Abstract—The effect of the relative intensity noise (RIN), trans-ferred from the pump to the signal, in 1-cm-long chip scale sil-icon Raman amplifiers is investigated in the presence of nonlinear losses. We show that due to the short waveguide length, the reduc-tion in fluctuations that normally occurs due to “walk-off ” between pump and signal waves in fiber amplifiers is inefficient in chip scale Raman amplifiers. In the counterpropagating pump configuration, which leads to minimum frequency RIN transfer, fluctuations up to 1.5 GHz are transferred from the pump to the signal. As a case study, the noise figure degrades by as much as 11 dB in the sil-icon waveguide with the free carrier life time of 0.1 ns, when it is pumped with a laser with a RIN value of 125 dB/Hz. Index Terms—Amplifier noise, nonlinear optics, Raman scat-tering, silicon-on-insulator technology. I