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结合色散光纤在线滤波和W型光纤的长波长截止性能,研究了W型色散光纤的带通滤波特性。选取SiO2作为纤芯,一定掺杂浓度的SiO2-F和SiO2-B2O3分别作为内外包层,经过设计,实现了带通滤波功能。通过有限元法仿真及数值计算,得出了基模的能量损耗谱及通带内外各个波长处的横截面能量分布图,其截止波长和带宽可以通过控制掺杂浓度和结构参数来调整。此外还进一步分析了纤芯半径大小及中心空气孔凹陷的存在对滤波特性的影响,结果表明,减小纤芯半径和增大空气孔能减小带宽和增大通带边缘的陡度。
Combined with the on-line filtering of dispersion fiber and the long wavelength cut-off of W-type fiber, the band-pass filtering characteristics of W-type dispersion fiber are studied. Select SiO2 as the core, a certain concentration of SiO2-F and SiO2-B2O3, respectively, as the inner and outer cladding, designed to achieve the band-pass filtering. Through the finite element method simulation and numerical calculation, the energy loss spectrum of the fundamental mode and the energy distribution of the cross section at each wavelength inside and outside the passband are obtained. The cutoff wavelength and bandwidth can be adjusted by controlling the doping concentration and the structure parameters. In addition, the influence of the size of the core radius and the hollow of the center air hole on the filter characteristics is further analyzed. The results show that reducing the core radius and increasing the air hole can reduce the bandwidth and increase the steepness of the passband edge.