中文摘要：

研究了在均匀光纤光栅中对称地插入两个π相移时透射谱的特性，通过矩阵法详细计算和分析透射谱双峰的波长间隔、线宽、波谷深与光栅各段长度的关系，获得设计双π相移光纤光栅的准则，即：双π相移光纤光栅的双峰波长间隔主要由两个π相移的距离决定，谱线宽和波谷深主要由光栅π相移两端的长度决定．

英文摘要：

The transmission spectra with dual peaks of double-π phase-shifted fiber Bragg gratings were analyzed. Two π phase shifts were placed in the grating symmetrically. The wavelength difference between the two peaks, the linewidth of the peaks, and the depth of the spectrum valleys are calculated by matrix method. Their relations with the length of each part of the gratings are analyzed specifically. The rules for designing the double-π phase-shifted fiber Bragg gratings are obtained that the wavelength difference between the two peaks depends on the distance of the two n phase shifts; the linewidth and the depth of the spectrum valleys are dependent on the length from the two n phase shifts to the ends of the fiber grating.