Theoretical and Numerical Study of the Threshold of Stimulated Brillouin Scattering in Multimode fibers

In this paper, we have studied theoretically and numerically the thresholds of stimulated Brillouin scattering in multimode fibers. With both the coupling among all optical modes and the effect of optical and acoustic mode field profiles on the Brillouin gain spectrums considered for the first time, we propose the corresponding transcendental equations for the Brillouin thresholds of continuous-wave signal under different conditions. Based on the theoretical results, it is concluded that Brillouin threshold in multimode fiber is determined by the constitution of the transverse modes in the signal. Moreover, the theoretical predictions are compared with the results obtained by numerically integrating the signal-Stokes power equations, and good agreements are achieved between them.