面向DAS系统的震源信号初至波到达时间拾取方法

First Arrival Time Pickup Method of Vibration Signals for Distributed Acoustic Sensing Systems

在基于相敏光时域反射计(Φ-OTDR)的光纤分布式声传感(DAS)系统定位震源二维空间位置方法中,由于干扰和噪声的影响,存在震源初至波到达光缆不同位置时间信息获取不准确的问题,带来较大的定位误差。针对DAS系统,提出了一种基于双边滤波边缘检测的震源初至波到达时间拾取方法。首先,将DAS系统采集的震源时空二维信号转换成灰度图,用双边滤波方法进行降噪,然后,应用基于Canny算子的边缘检测方法提取灰度图像中的边缘特征,来获得震源初至波到达时间。这种方法能够同时考虑时空二维数据的时间和空间整体特征,提高低信噪比信号初至波到达时间的拾取精度。现场实验表明,该方法对于受干扰和系统噪声影响的低信噪比信号,拾取的到达时间平均误差不超过3 ms,拾取精度比传统方法高,算法平均耗时仅需0.1 s,拾取时间短。

Twodimensional(2D)spatial position of a vibration source in an optical distributed acoustic sensing(DAS)system can be determined based on a phasesensitive optical timedomain reflectometer.However,due to interference and noise,this approach may acquire inaccurate arrival time information of the first arrival wave of the vibration source at different positions of the optical cable,resulting in large positioning errors.In this study,we propose a method of estimating the first arrival wave of the vibration source in a DAS system based on bilateral filtered edge detection.First,the spatiotemporal 2D signals collected by the DAS system were converted into a grayscale map,and then the bilateral filtering method was used to reduce the noise.The edge features in the grayscale image were extracted using a Canny operatorbased edge detection method to obtain the first arrival time of the source.The proposed method can simultaneously consider the overall temporal and spatial characteristics of spatiotemporal 2D data and improve the accuracy of low signaltonoise ratio signal of first arrival time pickup.Results show that for low signaltonoise ratio signals affected by interference and system noise,the average error for pickup arrival time does not exceed 3 ms,pickup accuracy is higher than that of the traditional method;the algorithm takes only 0.1 s on average,and pickup time consumption is low.