中文摘要：

采用一种改进的两级掺铒光纤放大器（EDFA）结构，构建了一套基于相干后向瑞利散射的分布式光纤传感入侵检测系统。首先通过OptiSystem软件从理论上仿真并得到了最佳的两段掺铒光纤（EDF）长度，然后依据相干后向瑞利散射信号的特点，提出了一种对信号进行分段处理的改进方法，解决了解调信号功率不均匀问题。针对光纤中散射体的随机性，建立了后向瑞利散射离散模型，采用蒙特卡罗方法对后向瑞利散射信号进行了数值模拟。实验表明，系统的定位精度达到15m，定位范围约为35km。本文系统有望广泛应用在输油管道、机场、监狱等重要场所的安全防范。

英文摘要：

The phase-sensitive optical time-domain reflectometer （φ-OTDR）, as a new distributed fiber sensor technology,has very significant practical value and economic value. A distributed optical fiber intrusion monitoring system based on coherent Rayleigh baekscattering is built by using a kind of improved two-stage EDFA structure. Firstly,the optimal two-stage fiber length is obtained by theoretical simulation with OptiSystem software. Then, an improved method by dividing the signal into several segments is proposed to process the Rayleigh backscattered signal based on the feature of coherent Rayleigh baekscattered signal,which solves the problem that the power of demodulation signal is inhomogeneous. According to the randomness of scattering along the fiber, a discrete model of Rayleigh backscattering is built and the Monte Carlo method is used to simulate Rayleigh backscattered signal. The experimental results show that an approximate sensing distance of 35 km with a spatial resolution up to 15 m is reached. This system is potential to be used widely in safety monitoring of oil pipeline, airport,jails andSO on.