Sun Xizi, Hong Xiaobin, Wang Sheng, Gao Xia, Guo Hongxiang, Li Yan, Qiu Jifang, Wu Jian
Opt Express. 2019 Apr 29;27(9):12899-12913. doi: 10.1364/OE.27.012899.
When studying the spatial resolution and Brillouin frequency shift (BFS) uncertainty in Brillouin optical time domain analysis (BOTDA) system with a hotspot, people usually focuses on the point with best performance in the hotspot and neglect the huge error around it. The error is caused by the Brillouin gain spectrum (BGS) contributed by both the hotspot and the ambient segment, which is distorted from standard Lorentzian curve. Due to the distortion of BGS, the estimated BFS near the hotspot is shifted from the actual value and results in BFS error along the fiber. The distorted BGS can be double-peak or single-peak curve that is dependent on both the length of the hotspot that contributes to BGS and the BFS difference between the hotspot and the ambient segment. A fitting technique considering the combined contributions of hotspot and ambient segment is proposed to recover the distorted BGS near the hotspot and evaluate BFS. It is demonstrated that BFS error around hotspot is greatly reduced compare to the conventional Lorentzian fitting and dual Lorentzian fitting schemes.
在研究具有热点的布里渊光时域分析（BOTDA）系统中的空间分辨率和布里渊频移（BFS）不确定性时，人们通常关注热点中性能最佳的点，而忽略其周围的巨大误差。该误差是由热点和周围区域共同贡献的布里渊增益谱（BGS）引起的，它偏离了标准洛伦兹曲线。由于BGS的畸变，热点附近估计的BFS偏离实际值，导致沿光纤的BFS误差。畸变的BGS可以是双峰或单峰曲线，这取决于对BGS有贡献的热点长度以及热点与周围区域之间的BFS差异。提出了一种考虑热点和周围区域联合贡献的拟合技术，以恢复热点附近畸变的BGS并评估BFS。结果表明，与传统的洛伦兹拟合和双洛伦兹拟合方案相比，热点周围的BFS误差大大降低。
