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针对目前受激布里渊散射(SBS)阈值研究主要针对单模光纤,而对多模光纤研究较少的现状,理论分析和计算了多模光纤SBS阈值特性。结果表明:对于多模光纤,由于其多个模式的布里渊增益谱叠加导致频谱展宽,其布里渊增益谱最大增益1.667 5×10-11 m/W较单模光纤偏低。根据多模光纤布里渊散射增益,通过SBS阈值公式获得了50/125μm阶跃折射率多模光纤和渐变折射率多模的SBS阈值与光纤长度、衰减系数、纤芯半径之间的关系。理论分析可知,阶跃折射率多模光纤的SBS阈值是渐变折射率多模光纤的4.5倍,更不容易发生SBS非线性效应。
In view of the fact that SBS thresholds are mainly for single-mode optical fibers and few researches on multi-mode optical fibers, the threshold characteristics of multi-mode optical fibers are analyzed and calculated theoretically. The results show that the maximum gain of Brillouin gain spectrum is 1.667 5 × 10-11 m / W, which is lower than that of single mode fiber for multimode fiber due to the broadening of the Brillouin gain spectrum due to the superposition of its multiple modes. According to the gain of Brillouin scattering of multimode fiber, the relationship between the SBS threshold and the fiber length, attenuation coefficient and core radius of 50/125μm step index multimode fiber and graded index multimode is obtained by SBS threshold formula. Theoretical analysis shows that the SBS threshold of step index multimode fiber is 4.5 times that of graded index multimode fiber, and the SBS nonlinearity is less likely to occur.