Abstract Time and spatial domains in ϕ -OTDR perturbation detection and recognition for pipeline and border security applications in very long fiber under test (FUT) environments have not been properly analyzed so far. We propose in this paper several issues and the corresponding solutions that should be considered in both domains when developing those applications. Solutions are based on: (1) the importance of differential signals in direct detected ϕ -OTDR systems; (2) dealing with the useless data acquired in the time domain; (3) dealing with the zero and ghost energy points along the FUT which will undoubtedly lead to hiding the real perturbation and reducing the potential of finding the exact location of the perturbation, respectively. Experimental results show that: (1) setting the appropriate experimental conditions (i.e., increasing the intensity of the perturbation and sampling at the minimum sampling rate that satisfies the Nyquist criterion) is a must; (2) the Kendall correlation-based technique on differential signals allows obtaining more significant data traces both in time and spatial domains; (3) combining both methods obtains further gains; (4) S-Scan algorithm accurately provides the time instant of the real perturbation by increasing the probability of detecting zero energy points and avoiding ghost energy points in further processing.

中文翻译：

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直接检测 ϕ-OTDR 系统的未发现问题和解决方案

摘要 φ -OTDR 扰动检测和识别中的时空域在极长的被测光纤 (FUT) 环境中的管道和边界安全应用中至今尚未得到适当的分析。我们在本文中提出了在开发这些应用程序时应该在这两个领域中考虑的几个问题和相应的解决方案。解决方案基于： (1) 差分信号在直接检测 ϕ -OTDR 系统中的重要性；(2)处理在时域中获取的无用数据；(3) 处理沿 FUT 的零能量点和鬼能量点，这无疑会分别导致隐藏真实扰动并降低找到扰动确切位置的可能性。实验结果表明：（1）设置合适的实验条件（即 必须增加扰动强度并以满足奈奎斯特准则的最小采样率进行采样；(2) 基于 Kendall 相关的差分信号技术允许在时域和空间域获得更重要的数据轨迹；(3) 结合两种方法获得进一步的收益；(4) S-Scan算法通过增加检测到零能量点的概率，避免进一步处理中的鬼能量点，准确地提供真实扰动的时刻。