We propose a novel interrogation technique for Distributed Acoustic Sensing (DAS) and demonstrate the detection and recognition of multiple vibration events over 50 km of SSMF. A differential-phase optical time-domain reflectometry ($\Delta \phi -$OTDR) approach is used. At the transmitter side, a continuous ultra-narrow-linewidth laser is modulated with polarization-multiplexed orthogonal binary sequences and at the receiver side, the back-scattered signal is captured through a polarization-diversity coherent mixer in a self-homodyne configuration. The detection of the full optical field vector and the use of an ultra-narrow-linewidth laser source enhance the sensitivity of the interrogating solution. A comparison of the experimental results to a simulation model is developed to better understand the noise limits. A low-complexity localization technique based on a multi-resolution approach is also presented. Major results include the identification of an engine noise, paving the way for numerous smart-city/industrial monitoring applications over deployed telecom fibres.

中文翻译：

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使用相干 Delta-Phi-OTDR 对长距离 SSMF 上的振动进行检测-定位-识别

我们提出了一种用于分布式声学传感 (DAS) 的新型询问技术，并演示了对 SSMF 50 公里以上的多个振动事件的检测和识别。使用差分相位光时域反射计 ($\Delta\phi -$OTDR) 方法。在发射端，一个连续的超窄线宽激光器被偏振复用正交二进制序列调制，在接收端，反向散射信号通过自零差配置的偏振分集相干混频器捕获。全光场矢量的检测和超窄线宽激光源的使用提高了询问解决方案的灵敏度。将实验结果与仿真模型进行比较，以更好地了解噪声限制。还提出了一种基于多分辨率方法的低复杂度定位技术。主要成果包括识别发动机噪音，为通过部署的电信光纤实现众多智慧城市/工业监控应用铺平了道路。