对相移长周期光栅进行了理论分析，在此基础上，运用传输矩阵法对它的透射光谱进行数值计算，分析了相移量大小、平均折射率变化以及光栅长度等结构参数变化对相移长周期光栅透射谱的影响，并根据这些变化规律适当调节它的结构参数，使其透射光谱与平坦 EDFA的目标光谱在一定程度上相符。平坦后的 EDFA增益谱在 34 nm范围内最大波动不超过 ±0.7 dB。根据此方法设计的增益平坦滤波器只包含一个器件，体积小，便于制造和封装，具有很好的市场应用前景。

Based on the theoretical analysis of phase-shifted long-period grating, the transmission spectrum of phase-shifted long-period grating is studied by transfer matrix method. The impacts of magnitude of phase shift, change of average refractive index and length of grating on transmission spectrum of phase-shifted long-period grating are discussed. According to the rules, the structure parameters of phase-shifted long-period grating are properly adjusted to make its transmission spectrum correspond with the target spectrum for flattening EDFA to some extent. Maximum fluctuation of flattened gain spectrum of EDFA does not exceed ±0.7 dB in the range of 34 nm. The gain flattening filter designed by this method only contains one device, and it has favorable market prospects due to small size and ease of manufacturing and packaging.