研究了局部压力条件下光纤光栅偏振相关损耗(PDL)的光谱表征。针对次峰现象,详细研究了压力幅度、受压长度和受压位置对次峰产生条件的影响。采用传输矩阵法进行了数值模拟,理论分析和数值仿真显示,受压长度对次峰随压力变化的幅度和波长位移灵敏度有重要影响。在不同的受力长度下,产生次峰需要的受力幅度不同。该研究对利用PDL次峰进行传感具有很好的理论指导意义。 The spectral characterization of polarization dependent loss (PDL) of a fiber grating under local pressure conditions was investigated. In view of the second peak phenomenon, the influences of pressure amplitude, compression length and compression position on secondary peak generation conditions are studied in detail. The transmission matrix method is used to conduct numerical simulation. The theoretical analysis and numerical simulation show that the compression length has an important influence on the magnitude of sub-peak pressure variation and the wavelength sensitivity. Under different stress lengths, the magnitude of force required to generate secondary peaks is different. The study of the use of PDL secondary peak sensing has a good theoretical guidance.