We propose a multipath distributed acoustic sensing (MP-DAS) system based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) and frequency division multiplexing (FDM) technique. With FDM introduced to Φ-OTDR, simultaneously monitoring of multipath vibration is realized with flexible functionality. In the proposed MP-DAS system, the parameters of each path can be adjusted individually according to the path's specific monitoring requirement. A dual path Φ-OTDR system with 1 km and 22 km measurement distance is demonstrated in the experiment. Through heterodyne detection and FDM technique, both amplitude and phase information are obtained for event locating and vibration sensing in each of the two paths, with a spatial resolution of 5 m and 10 m respectively. With changing optical power and pulse width of one path, its influence on the other path is discussed and analyzed. This proposed MP-DSA system based on FDM technique provides an efficient and cost-effective way for upgrading a conventional single DAS into an integrated DAS network, which shows great potential in many applications such as modern city civil structure monitoring with different demands.

我们提出了一种基于相敏光时域反射仪（Φ-OTDR）和频分复用（FDM）技术的多径分布式声感测（MP-DAS）系统。通过在Φ-OTDR中引入FDM，可以通过灵活的功能同时监视多径振动。在建议的MP-DAS系统中，可以根据路径的特定监视要求单独调整每个路径的参数。实验中演示了具有1 km和22 km测量距离的双路径Φ-OTDR系统。通过外差检测和FDM技术，可以获得振幅和相位信息，用于两条路径中的每条路径中的事件定位和振动感测，其空间分辨率分别为5 m和10 m。随着一条路径的光功率和脉冲宽度的变化，讨论并分析了其对另一条路径的影响。所提出的基于FDM技术的MP-DSA系统为将传统的单个DAS升级为集成DAS网络提供了一种有效且具有成本效益的方式，这在许多应用（例如具有不同需求的现代城市土木结构监控）中显示出巨大的潜力。