非线性效应对前向受激布里渊散射分布式传感的影响

Influence of nonlinear effects on forward stimulated Brillouin scattering distributed sensing

以光力时域分析传感器为例,实验研究了非线性效应对前向受激布里渊散射分布式传感的影响,并给出了优化过程.前向受激布里渊散射的产生由于增益系数低,需要较高的脉冲功率(W级)进行激发,由于读取脉冲光与散射光同向传输特性,高功率脉冲将诱发前向受激布里渊散射传感系统中各种非线性效应.借鉴前人激活-读取分离技术,可有效避免激活脉冲非线性效应的影响,然而读取脉冲非线性效应对传感性能仍存在直接影响.基于此,本文研究了不同读取脉冲功率条件下,非线性效应对前向受激布里渊散射传感性能的影响及其物理机理;具体展示了~4.7 km标准单模光纤中,一、二阶散射边带随读取脉冲功率的演化过程,最终找到了优化区间,得到较为完美的本地增益谱,并且延长了传感距离.

The influences of nonlinear effects on sensing performance of forward stimulated Brillouin scattering(FSBS) are investigated using opto-mechanical time-domain analysis sensor,which is taken for example.The excitation of FSBS often requires high pulse power(at Watt level) because of the lower gain coefficient.Owing to the co-propagation of reading pulse and scattered light,high-power activation pulses will induce various nonlinear effects in an FSBS sensing system.Using the reported method based on activation-reading timedomain separation,the influences of nonlinear effects due to activation pulses can be effectively avoided.However,the nonlinear effects of reading pulses directly affect the sensing performance.Based on this consideration,we study the influences of nonlinear effects on FSBS sensing and their physical mechanisms under different values of peak power of reading pulses;the variation process of the 1st-and 2nd-order FSBS spectrums along ~4.7 km standard single-mode fiber are revealed in detail.Finally,the optimal region is found,in which a perfect FSBS local spectrum is obtained,and the sensing distance can be extended.