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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。
In the design of multi-channel fiber Bragg grating (FBG) filters, an increase in the number of channels leads to a multiple of the maximum depth of modulation of the refractive index, resulting in a physically unrealizable implementation. Therefore, a multi-channel FBG filter design method based on Particle Swarm Optimization (PSO) and direct design method is proposed. This method minimizes the maximum modulation depth of refraction index, introduces a group of group delay parameters into the target reflection spectrum, allocates the appropriate group delay parameters for each channel, and establishes the optimization model of group delay parameters. Particle swarm optimization algorithm is used to calculate the optimal distribution of the delay parameters of each channel group, to improve the degree of uniform distribution of the refractive index modulation depth and to reduce the maximum refractive index modulation depth to the physically achievable range. The simulation results show that the two FBG filters designed with 40 channels and 106 channels have good reflection spectrum uniformity and the maximum depth of refraction modulation is below 0.001.