Gabai Haniel, Shpatz Itai, Eyal Avishay
Opt Lett. 2017 Nov 1;42(21):4529-4532. doi: 10.1364/OL.42.004529.
Distributed acoustic sensing (DAS) via optical fibers makes use of Rayleigh backscattering for the detection of acoustic waves that interact with the fiber along its entire length. The random nature of Rayleigh backscattering leads to nonuniform performance along the fiber and, occasionally, to complete signal fading. In addition, distance-dependent signal-to-noise (SNR) degradation is always present due to propagation loss. In contrast, using arrays of discrete reflectors [such as weak fiber Bragg gratings (FBGs) with equal center wavelengths] offers deterministic performance which can be designed to be uniform along the fiber. Here we describe an approach for implementing Rayleigh-based discrete reflectors that can offer enhanced detection performance in selected regions. It is based on enclosing sections of the fiber in acoustically insulated boxes to create lumped Rayleigh reflectors. Besides diminishing the randomness in detection sensitivity, the method enables increasing the detection SNR far beyond the typical value for Rayleigh-based DAS and obtaining sensitivities comparable with discrete reflectors. The proposed method was successfully tested via both simulation and experiment.
基于光纤的分布式声学传感（DAS）利用瑞利背向散射来检测沿光纤全长与光纤相互作用的声波。瑞利背向散射的随机性导致沿光纤的性能不均匀，偶尔还会导致信号完全衰落。此外，由于传播损耗，与距离相关的信噪（SNR）劣化总是存在。相比之下，使用离散反射器阵列[例如具有相等中心波长的弱光纤布拉格光栅（FBG）]可提供确定性性能，其可以设计为沿光纤均匀。在这里，我们描述了一种实现基于瑞利的离散反射器的方法，该方法可以在选定区域提供增强的检测性能。它基于将光纤段封装在隔音盒中以创建集总瑞利反射器。除了减少检测灵敏度的随机性之外，该方法还能够将检测SNR提高到远超过基于瑞利的DAS的典型值，并获得与离散反射器相当的灵敏度。所提出的方法通过模拟和实验都成功进行了测试。
