在多通道光纤布拉格光栅（FBG）滤波器的设计中，通道数目的增加会导致最大折射率调制深度的成倍增长，从而造成物理上的不可实现。为此，提出一种基于粒子群算法(PSO)与直接设计方法相结合的多通道FBG滤波器设计方法。该方法以最小化最大折射率调制深度为优化目标，在目标反射谱中引入一组群时延参数，为每个通道分配合适的群时延参数，建立群时延参数的优化模型。通过粒子群算法计算得到各通道群时延参数的优化分配值，提升折射率调制深度的均匀化分布程度，促使最大折射率调制深度降低到物理可实现的范围内。仿真实验结果表明设计的40通道数、106通道数的两种FBG滤波器的反射谱均匀性好，最大折射率调制深度均降到0.001以下。

With the increasing number of channels, fabricating a multi-channel fiber Bragg grating (FBG) filter requires a considerably high maximum index modulation, which is beyond a physically realizable level. Hence, an effective optimization method based on particle swarm optimization (PSO) algorithm and direct design method to design a multi-channel FBG filter is proposed. By introducing the tailored group delay coefficients into the target reflectivity spectrum, a mathematical model aiming at minimizing the maximum index modulation of the grating is established. The PSO algorithm is employed to find the optimal group delay parameter for each channel. It leads to a more even distribution of the refractive index modulation, thereby reduces the maximum index modulation to a physically realizable level. Design examples of the 40-channel and 106-channel FBG filters both with uniform reflection spectra demonstrate that the proposed method yields a remarkable reduction in the maximum index modulation which is below 0.001.