非对称切趾对啁啾光纤光栅特性优化的分析

基于对啁啾光纤布拉格光栅反射谱和时延曲线的分析,引入非对称切趾技术。综合时延曲线纹波和反射谱纹波平滑两方面考虑,将对称切趾技术的最佳切趾比例、左移和右移两种非对称切趾技术以及采用不同切趾函数对光纤光栅特性参量的优化效果进行了分析和比较。结果表明,与对称切趾相比,左移非对称切趾可避免对称切趾中为增大反射谱带宽而减小切趾比例使时延纹波增大的缺点,在保持反射谱纹波基本不变的前提下将时延曲线纹波降低了43.5%(与实验结果39.9%相吻合)。此外,与仅用汉明函数切趾相比,光纤光栅左端采用超高斯函数、右端采用汉明函数的非对称切趾方式使反射谱平坦部分纹波减小了89.3%,对应的时延曲线拟合误差减小了16.7%,获得了更好的优化效果。

Optimization of Chirped Fiber Bragg Gratings by Asymmetrically Apodization Method

Asymmetrical apodization method is introduced to optimize chirped fiber Bragg gratings based on the analysis of its reflectivity spectrum and time delay response.The optimization effects for grating parameters,by the optimum apodization ratio of the symmetrical apodization,the left-shifted and right-shifted asymmetrical apodization methods and different apodization functions,are analyzed and compared.The results show that,compared with symmetrical apodization method,the asymmetrical apodization method can avoid the disadvantage of the former method that widens the reflectivity bandwidth by reduction of apodization ratio,which meanwhile increases the time delay ripple.The left-shifted apodization method can reduced the time delay ripple by 43.5%,adjacent with the experimental result of 39.9%,while the refectivity spectrum is nearly unchanged.Furthermore,better performance can be obtained with super-Gaussian function on left-side and Hamming function on right-side of chirped fiber Bragg gratings than Hamming function on both sides.The plain part of the reflectivity ripple is reduced 89.3%,as well as fitting error of group delay ripple 16.7%.