单点振动激励下分布式光纤声传感系统的响应特点

Characteristics of Fiber Distributed Acoustic Sensing System under Point-driven Single-frequency Oscillation

基于相干光时域反射技术的分布式光纤声传感系统是检测环境振动的重要工具,但系统响应受干涉光强波动干扰,给定量检测带来困难。针对单频连续点振源这一较为典型的传感场景,研究商用相干光时域反射系统的响应特性。实验表明,系统可以准确探测振动的位置和中心频率。实验探索了两种信号处理方法。信号频谱的时域平均可以还原出响应和振幅间的线性关系;一定范围内的空间域响应分布保留了振动强度分布特点。两种方法都较好地克服了信号波动的影响,将有助于系统实现更为精确一致的测量。

Distributed fiber acoustic sensing based on coherent optical time-domain reflectometry(C-OTDR) is an important tool for vibration detection. However, the response of the C-OTDR system is affected by the intensity fluctuation of the interfering light, which makes quantitative measurement difficult. The response characteristics of a commercial C-OTDR system in the typical case of a single-frequency continuous point vibration source are studied. Experimental results show that the system can detect the location and the central frequency of the vibration accurately. And two signal processing methods are examined. The linear relation between the response and the excitation amplitude can be restored through averaging the spectra in time domain. The distribution of vibration amplitudes is maintained by the spatial distribution of the response within a certain range. The two methods can negate the influence from the signal fluctuation satisfactorily, which is helpful to realize more consistent and precise measurement of the system.