Hong Xiaobin, Lin Wenqiao, Yang Zhisheng, Wang Sheng, Wu Jian
Opt Express. 2016 Sep 5;24(18):21046-58. doi: 10.1364/OE.24.021046.
The tolerance of the non-local effect in the BOTDA method using a dual-tone probe wave with fixed frequency separation is theoretically and experimentally investigated in this paper. The presented analysis points out that when the sensing fiber consists of two long fiber segments with large BFS difference (> 100 MHz), there will always be only one probe tone interacting with the pump pulse in the front fiber segment. Therefore, although the pulse distortion problem can still be overcome in this case, the conventional non-local effect would impose systematic error on the estimated BFS of the hotspot located at the end of the front fiber segment. For the purpose of avoiding the impact of non-local effect and eliminating the pump distortion problem simultaneously when using high probe power, a novel method based on a four-tone probe wave is proposed, in which the probe light consists of two pairs of orthogonally-polarized dual-tone probe waves with opposite frequency scanning direction. The experimental results demonstrate that the proposed method is capable of realizing 2 m spatial resolution over 104-km-long sensing fiber without the impact of non-local effect.
本文对使用具有固定频率间隔的双音探测波的布里渊光时域分析（BOTDA）方法中的非局部效应耐受性进行了理论和实验研究。所给出的分析指出，当传感光纤由两个布里渊频移（BFS）差异较大（>100 MHz）的长光纤段组成时，在前光纤段中总是只有一个探测音与泵浦脉冲相互作用。因此，尽管在这种情况下脉冲失真问题仍然可以克服，但传统的非局部效应会对位于前光纤段末端的热点的估计BFS施加系统误差。为了在使用高探测功率时避免非局部效应的影响并同时消除泵浦失真问题，提出了一种基于四音探测波的新方法，其中探测光由两对具有相反频率扫描方向的正交偏振双音探测波组成。实验结果表明，所提出的方法能够在104公里长的传感光纤上实现2米的空间分辨率，而不受非局部效应的影响。
