Comparison between threshold and sensitivity of stimulated Brillouin scattering at different pumping configurations in high-power double-clad fiber lasers

Theoretical analysis of stimulated Brillouin scattering (SBS) in high power ytterbium-doped double-clad (YDDC) fiber lasers is presented by solving the steady-state rate equations with regard to SBS at different pumping configurations. The behavior of Brillouin Stokes power growth along the fiber is investigated and the SBS threshold power is quantitatively compared at forward, backward and bi-directional pumping configurations. It is shown that the backward pumping configuration has higher SBS threshold power than two others. Also. The effect of cavity parameters such as cavity length, front mirror reflectivity, dopant concentration and laser linewidth at different pumping configuration have been studied. It can be seen although the backward puming has higher SBS threshold but its sensitivity to cavity parameters is higher than other pumping configuration which is a negative impact for cavity designing.