Optimization of Multi-Pump Raman Amplifiers

The utilization of high-gain bandwidth in fiber Raman amplifiers (FRA) requires multiple pumps at different wavelengths and careful adjustment of the individual pump powers [1-2]. Due to the large number of varying, partly unknown parameters, this is only feasible with the help of special optimization algorithms [3-4]. It is essential that such optimization routines consider pump-pump and pump-signal Raman interactions. However, other physical effects, whose impact is a priori unknown within the scope of the optimizer, can have a significant influence on the performance of the Raman amplifier. For instance, signal-signal Raman interactions, Rayleigh and Brillouin scattering, and power-related variations of broadband pump sources can cause considerable amplifier degradations. Therefore, it is essential that those effects are considered carefully and that realistic fiber and component characteristics are used to obtain meaningful optimization results. In this paper, we present a new technique for automatic optimization of multi-pump Raman amplifiers complying with the constraints listed above while keeping the simulation time within reasonable limits. Our multistep approach considers first, fiber attenuation and interactions between WDM signals and Raman pumps, and then, any other effects by treating them as external perturbation in an iterative process. Results of pump optimizations are shown demonstrating how various physical effects can influence the design of multi-pump FRAs.