多模光纤布里渊散射阈值理论分析与计算

Theoretical Analysis and Calculation of the Stimulated Brillouin Scattering Threshold in Multimode Fiber

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。

At present,researches of stimulated Brillouin scattering(SBS)threshold are mainly concentrated in the single mode fiber,whiel less researches on multimode fibers.Based on which,a theoretical analysis and calculation of the SBS threshold is conducted in this paper.For multimode optical fiber,multiple modes of the Brillouin scattering superposition lead to spectrum broadening,and the peak value of the Brillouin gain spectrum is 1.667 5×10-11 m/W lower than that of the single-mode optical fiber.Then according to the formula of the SBS threshold and the peak value of the Brillouin gain,the SBS threshold of 50/125μm multimode optical fibers with step index or graded index is calculated.And then the relationships of the SBS threshold with the fiber length,attenuation coefficient and the core radius are obtained.According to the theory analysis,the SBS threshold of step index multimode fiber is 4.5times of that of the graded index multimode fiber,and less prone to occur the SBS nonlinear effect.