高消光比脉冲光调制提升BOTDR系统性能研究

Research on improving performance of BOTDR system usinghigh extinction ratio pulse modulation

传统的布里渊光时域反射(BOTDR)系统普遍采用电光调制器(EOM)产生探测光脉冲,存在探测光消光比较低的缺点,影响系统的测量精度和传感距离。提出利用基于半导体光放大器(SOA)的脉冲光调制方法产生高消光比脉冲光,设计基于相干探测的脉冲光消光比测量方案,同时搭建了BOTDR传感系统,对本脉冲光调制方法进行了性能测试。实验结果表明,相对于传统的EOM调制方法,采用本调制方法时,产生的探测光消光比提升了16 dB,10.7 km传感光纤末端的布里渊频移波动由10.6 MHz减小至5.7 MHz,在同等测量条件下,传感距离由10.7 km提升至27 km。研究表明,基于SOA的脉冲光调制方法可显著提高探测光消光比,进而优化BOTDR系统的测量精度和传感距离。

In a traditional BOTDR system,an electro-optic modulator(EOM) is generally used to generate probe pulse, which brings the disadvantage of relatively low extinction ratio of probe pulse and affects the measurement accuracy and sensing distance of the system. A pulse modulation method based on semiconductor optical amplifier(SOA) was proposed to produce pulse with high extinction ratio. A scheme based on coherent detection was designed for measuring the extinction ratio of probe pulse. Meanwhile a BOTDR sensing system based on SOA was built to test the performance of the method. Experimental results show that compared with the traditional EOM modulation method, the extinction ratio of probe pulse generated by the proposed modulation method is increased by 16 dB. Furthermore, the Brillouin frequency shift fluctuation at the sensing fiber end(10.7 km) is reduced from 10.6 MHz to 5.7 MHz and the sensing distance is increased from 10.7 km to 27 km under the same measurement conditions. The research shows that the pulse modulation method based on SOA can significantly increase the extinction ratio of probe pulse and then optimize the measurement accuracy and sensing distance of BOTDR system.