基于射线光学和波动光学理论分析了多模光纤的布里渊散射特性, 提出了确定布里渊散射角取值范围的方法；推导了阶跃型和渐变型多模光纤不同模式群布里渊频移、线宽、散射谱和散射功率的表达式.结果表明, 阶跃型和渐变型多模光纤布里渊散射角的最大取值范围为全反射临界角的2倍到π；阶跃型光纤的布里渊频移、线宽、归一化峰值增益和散射功率随模式群的变化比渐变型光纤缓慢, 且随着模式群编号的增加, 阶跃型光纤的上述参量分别在11.084-10.932 GHz、21.760-21.168 MHz、1-0.933和1.990×10-9-1.857×10-9 W范围内呈曲线下降；渐变型光纤的上述参量分别在11.064-10.969 GHz、21.683-21.314 MHz、1-0.957和2.052×10-9-1.965×10-9 W范围内呈直线下降.

The characteristics of Brillouin scattering in silica multimode optial fiber were analyzed based on the ray optics and wave optics theory.A method to determine the range of Brillouin scattering angle was proposed and the expressions of Brillouin shift, Brillouin linewidth, Brillouin scattering spectrum and scattering power of different mode group in step and graded multimode optical fibers are deduced and simulated.The results show that the maximum range of Brillouin scattering angle in step and graded fibers is from twice of the critical incident angle of total reflection to π, and with the increasing of mode group number, Brillouin shift, Brillouin linewidth, normalized peak gain and scattering power of step fiber change more slowly than those of graded fiber, and the above parameters of step fiber decrease nonlinearly in the ranges of 11.084 GHz to 10.932 GHz, 21.760 MHz to 21.168 MHz, 1 to 0.933 and 1.990×10-9 W to 1.857×10-9 W, but the correspending parameters of graded fiber decrease linearly in the ranges of 11.064 GHz to 10.969 GHz, 21.683 MHz to 21.314 MHz, 1 to 0.957 and 2.052×10-9 W to 1.965×10-9 W, respectively.