基于SOA脉冲调制的BOTDR应变检测系统

BOTDR Strain Detection System Based on SOA Pulse Modulation

电光调制器调制光脉冲时易受偏振态与偏压影响,造成调制脉冲平均功率与消光比不稳定,影响检测系统稳定性,实际中需通过复杂算法校正。提出半导体光放大器调制光脉冲的方法,通过改变注入泵浦电流调制光脉冲,采用相干探测结合微波频率扫描方法,获取不同频率点下自发布里渊散射信号,经洛伦兹拟合得到布里渊散射谱,实现光纤沿线布里渊频移解调,并搭建了基于半导体光放大器的BOTDR分布式应变检测系统。实验中选取2.943 km光纤末端施加500με,频移测量误差在±0.5 MHz范围内。研究表明可实现稳定应变检测。

The light pulse modulated by Electric Optic Modulator（ EOM） is susceptible to polarization and bias problems,which may cause the instability of average power and extinction ratio of the modulated pulse.Thus,the stability of detecting system is influenced,which needs to be corrected by complex algorithms. In this paper,we propose a new method that modulates probe optical pulse using a semiconductor optical amplifier（ SOA） by changing the pump current. The coherent detection combined with the microwave frequency scanning method is used to obtain the spontaneous Brillouin scattering signal at different frequencies,and the scattering spectrum is obtained by Lorenz fitting to demodulate the frequency shift along the optical fiber. Finally,a BOTDR distributed strain detecting system based on SOA is built,and a strain of 500 με is imposed at the end of 2.943 km fiber. The experimental results show that a stable strain detection is achieved with a measurement error in range of ±0.5 MHz.