根据耦合模理论，深入研究了横向压力作用下光纤布拉格光栅(FBG)的反射偏振相关损耗(RPDL)特性，对不同横向压力下的RPDL分别进行了数值模拟。模拟结果表明，RPDL对横向压力的响应非常敏感，压力变化时其峰值高度和主峰位置均发生较大的变化。对此进行大量的实验验证，实验结果与理论分析相符；并且实验结果显示RPDL峰高变化和峰位变化曲线在一定范围内均呈很好的线性关系。从而可以利用RPDL特性实现对外力场信息变化的灵敏监测。

According to coupled mode theory, the reflected polarization dependent loss (RPDL) property of fiber Bragg grating (FBG) under lateral force has been studied deeply. The numerical simulation of the RPDL under different lateral force is developed, and the simulation results show that the response of RPDL is very sensitive to lateral force. Peak height and peak position change greatly with force. Conducting a large number of experiments, experimental results accord with theoretical analysis; moreover, the results show the changing curves of RPDL peak height and peak position within a certain range are in good linear relationship. Therefore RPDL can achieve the sensitive monitoring to the changes of force field information, and a new method for FBG to demodulate exactly is provided.