Optical fiber distributed acoustic sensing (DAS) based on phase sensitive optical time domain reflectometry (ϕ-OTDR) has a great demand in many application fields with large signals, such as railway safety monitoring, cable vibration detection, etc. However, due to the inherent limits of phase unwrapping algorithm, the large signal whose phase change exceeds π cannot be recovered correctly by DAS. In this work, the differential-unwrapping-integral (DUI) algorithm is proposed and demonstrated to replace the traditional unwrapping algorithm for large signal recovery. By utilizing differential operation to compress the signal amplitude, the large phase signal can be converted into small signal which can be recovered through unwrapping. Then, multiple integral operations and polynomial fitting compensation algorithm are applied onto the differential signal to recover the original phase signal without any signal-to-noise ratio(SNR) sacrificed. In theory, the maximum measurable phase of DUI can be improved 1390 times compared with traditional DUI algorithm. Further, the experimental results demonstrate that the dynamic range of DAS with DUI can reach up to 131.7 dB. Moreover, DUI algorithm has been tested and verified in the field test for recording the digging signals with large amplitude. This scheme can be applicable for all phase-demodulation-based sensing techniques without increasing the system complexity.

中文翻译：

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具有差分展开积分算法的大动态范围光纤分布式声学传感 (DAS)

基于相敏光时域反射计（φ-OTDR）的光纤分布式声学传感（DAS）在铁路安全监测、电缆振动检测等许多大信号应用领域有着巨大的需求。相位解缠算法的固有限制，DAS无法正确恢复相位变化超过π的大信号。在这项工作中，提出并演示了差分解缠积分 (DUI) 算法以替代传统的解缠算法以进行大信号恢复。利用微分运算对信号幅度进行压缩，可以将大相位信号转换为小信号，并通过展开恢复。然后，对差分信号应用多重积分运算和多项式拟合补偿算法，在不牺牲任何信噪比（SNR）的情况下恢复原始相位信号。理论上，DUI 的最大可测相位与传统 DUI 算法相比可提高 1390 倍。此外，实验结果表明，带有 DUI 的 DAS 的动态范围可以达到 131.7 dB。此外，DUI算法已经在现场测试中得到了测试和验证，用于记录大振幅的挖掘信号。该方案可适用于所有基于相位解调的传感技术，而不会增加系统复杂性。DUI 的最大可测相位与传统 DUI 算法相比可提高 1390 倍。此外，实验结果表明，带有 DUI 的 DAS 的动态范围可以达到 131.7 dB。此外，DUI算法已经在现场测试中得到了测试和验证，用于记录大振幅的挖掘信号。该方案可适用于所有基于相位解调的传感技术，而不会增加系统复杂性。DUI 的最大可测相位与传统 DUI 算法相比可提高 1390 倍。此外，实验结果表明，带有 DUI 的 DAS 的动态范围可以达到 131.7 dB。此外，DUI算法已经在现场测试中得到了测试和验证，用于记录大振幅的挖掘信号。该方案可适用于所有基于相位解调的传感技术，而不会增加系统复杂性。