Numerical modeling and optimisation of cascaded CW Raman fiber lasers

Summary form only given. Stimulated Raman scattering (SRS) in optical fibers represents a very interesting method to amplify optical signals and to generate new laser wavelengths. The availability of high-power diode lasers and high-reflectivity fiber Bragg gratings makes possible the realization of nested cavities in which five or six Stokes lines can simultaneously resonate, so that the pump power can be very efficiently converted to the highest-order Stokes line. The Raman fiber laser can be very useful as a pump for high-power and remotely-pumped erbium amplifiers and for the implementation of distributed amplifiers. We present a numerical model which applies to a nested Fabry-Perot fiber Raman cavity using Bragg reflectors. At variance with previous models, our model takes into account at the same time all the forward and backward Raman scattering contributions. We consider the case in which, starting from a pump source at 1117 nm, a two-step cascade leading to a 1240 nm output or a five-step cascade leading to a 1480 nm output are considered.