Simulation and experimental validation of gain saturation in Raman fiber amplifier

In this paper, the effect of the large signal power on the Raman amplification is simulated utilizing OptiSystem. Two types of Raman amplification systems are simulated; average power Raman amplifier model (APA-RFA) and bidirectional-fiber Raman amplifier model (Bi-Fiber RFA). A comparison is made between these two kinds of amplifiers under the same input power condition. As a result the saturation mechanism due to the large input signal is recognized in bidirectional fiber Raman amplifier model. This saturation is due to the stimulated Brillouin scattering that occurred once the input signal power exceeds the stimulated Brillouin scattering threshold (SBS_TH). On the other hand, the average power Raman amplifier model exhibits constant Raman gain with the input signal power variation as the stimulated Brillouin scattering is not considered in this model. Finally, experimental results show significant agreement with the simulation results of the bidirectional fiber Raman amplifier model.