提出一种利用相位载波的调制解调技术实现白光干涉系统复用的周界安防新方法.该系统在单芯反馈式白光干涉系统的若干感应端，分别串接工作在不同频率的相位调制器.首先利用相位调制技术，将不同干涉子系统的感应端的触发信号从频域上分开；再使用相位解调技术，从同一干涉系统输出信号中获得相应于不同感应端的独立时域信号.实验中通过布设在现场的传感光纤对区域环境振动实现实时记录，用白光干涉方法实现振动信号的提取，利用相位载波复用实现不同区域的定位.理论分析和测试结果表明：通过相位载波复用技术，实现不同传感端共用一套干涉系统的方法，可以显著减小周界安防系统的复杂程度，降低系统成本；该方法能对环境触发信号进行实时监控，并能快速，有效地确定扰动信号的所属区域，具有较高的灵敏度，有利于在大区域，长距离的监控领域获得实施.

A novel method to measure the absolute phase shift on reflection of thin film is presented utilizing a white-light interferometer in spectral domain. By applying Fourier transformation to the recorded spectral interference signal, we retrieve the spectral phase function \phi which is induced by three parts: the path length difference in air L the effective thickness of slightly dispersive cube beam splitter T_{eff} and the nonlinear phase function due to multi-reflection of the thin film structure. We utilize the fact that the overall optical path difference (OPD) is linearly dependent on the refractive index of the beam splitter to determine both L and T_{eff}. The spectral phase shift on reflection of thin film structure can be obtained by subtracting these two parts from \phi. We show theoretically and experimentally that our new method can provide a simple and fast solution in calculating the absolute spectral phase function of optical thin films, while still maintaining high accuracy.