提出了一种基于大功率超窄线宽单模光纤激光器的φ-光时域反射计光纤分布式传感系统。传感光缆采用普通单模光纤制成的直径3 mm的细光缆,并埋设于室外。入侵者走在光缆上面或附近产生的压力(振动)导致光纤中瑞利散射光相位发生变化,由于干涉作用,光相位变化将引起光强度的变化,通过实时将当前时刻的φ-光时域反射计后向瑞利散射信号与其前一时刻(时间间隔0.1 s)的后向瑞利散射信号连续相减检测这种干涉效应来定位入侵位置。经适当的数据处理后,该传感系统定位精度可达到50 m(为目前报道的φ-光时域反射计传感系统最高定位精度),定位范围可达到14 km,信噪比约为12 dB,且灵敏度较高。该系统可望能广泛用于**基地、国界、核设施及监狱等重要场所的安全防范。

A phase-sensitive optical-time-domain-reflectometer (φ-OTDR) using a fiber laser with high power and narrow linewidth is described. The sensing element is a single-mode telecommunication fiber cable with a 3 mm diameter buried outdoors. The phase changes of Rayleigh scattering light resulting from the pressure (vibration) of the intruder on the ground immediately above or near the buried fiber. By subtracting a present φ-OTDR trace signal from an earlier one with a time difference of 0.1 s, the system can locate the intrusion point where the optical intensity will change for the reason of interference. By processing the returned signal properly, a distance range of 14 km can be reached, with the best spatial resolution of ～50 m reported to date, and a signal-to-noise ratio of ～12 dB, to the best of our knowledge. Such a distributed sensing system is anticipated to be used widely in safety monitoring of military bases, national boarders, nuclear facilities, electrical power generation stations, jails, et al..