【作者】 王鹏；

【导师】 陈向飞；

【作者基本信息】 清华大学 ， 电子科学与技术， 2005， 硕士

【摘要】 因为色散斜率随着光纤长度、光纤非线性、信号功率波动、光纤类型和温度等因素的变化而变化,所以在未来动态可重构光网络中,色散斜率的补偿必须是动态的,可调谐的。而光纤光栅因其低损耗,低光纤非线性,小尺寸,价格便宜等优点,成为可调谐色散斜率补偿模块的有力竞争方案。为了利用光纤光栅进行可调谐色散斜率补偿,光栅群时延谱曲线必须是波长的三次函数,也就是说在各个波长处具有不同的色散斜率值。为了达到这个目的就必须实现沿光栅方向啁啾系数发生改变。本论文采用的方式是利用非线性啁啾的光纤光栅,不同工作点、即不同波长处的色散斜率不一样,只要改变光栅的工作点就可以实现可调谐色散斜率补偿。非线性啁啾的引入是制作这类非线性啁啾光纤光栅的难点,本论文利用具有取样周期啁啾的取样光纤光栅在其某个特定反射带内引入所需要的非线性啁啾。具有取样周期啁啾的取样光纤光栅可以等效为一个取样周期没有啁啾的取样光栅,而该等效取样光栅的各个反射带具有和其傅立叶级次成正比的等效光栅周期啁啾。与光栅周期啁啾的光纤光栅相比,取样周期啁啾光纤光栅具有设计和制作灵活、不需要啁啾相位模板、取样周期啁啾比光栅周期啁啾在实验上更容易控制等优点。与复杂应变分布的啁啾光栅相比,具有结构简单、体积小、易封装、无辐射模损耗等优势。本论文提出了一种基于取样光纤光栅的可调谐色散斜率补偿器的全新设计方法。对具有任意形式的三次群时延谱曲线,给出了利用等效啁啾法来设计目标取样光纤光栅的具体方法。对于最简单形式的三次群时延谱曲线给出了解析表达式,对于更为复杂的群时延谱曲线利用相同思路数值求解即可。对于某些情形,取样函数必须用等效重构算法进行修正。更近一步,本论文给出了利用上述全新设计方法制作的取样光纤光栅的实验结果。最终的实验结果不仅证明了设计方法的正确性,也完全达到了设计要求。实验部分的结论还对围绕取样光纤光栅所进行的其它研究工作有一定的借鉴意义。更多还原

【Abstract】 In the future reconfigurable optical networks, dispersion-slopecompensation must be tunable, because dispersion-slope varies with thevariation of optical fiber length, optical nonlinearity, signal power, opticalfiber type and the temperature of environment. Fiber Bragg Grating (FBG) is acompetitive solution to the tunable dispersion-slope compensation modulebecause of its low loss, low optical nonlinearity, small footprint and low cost.In order to compensate dispersion-slope with FBG, group delay curvemust be a third-order function of wavelength, which means thatdispersion-slope varies at different wavelength. To satisfy this requirement,the chirp of the FBG must vary along the FBG length. In this paper, by usingthe nonlinearly chirped FBG, dispersion-slope varies at different wavelength.Thus, dispersion-slope compensation can be tunable by varying the workingpoint of the FBG.The key point of fabrication of this kind of nonlinearly chirped FBG ishow to introduce the nonlinear chirp. In this paper, the introduction ofnonlinear chirp in some reflection band is realized by chirping the samplingperiod of Sampled Fiber Bragg Grating (SFBG). By properly designing chirpin the sampling period, the grating produce an equivalent nonlinear chirpprofile within reflection bands with non-zero Fourier orders. Compared withFBG with chirp in the grating period, SFBG with chirp in the sampling periodis more advantageous in that it is flexible in designing and fabrication, that itdoes not need chirped phase masks, and that the sampling period is easier tocontrol than the grating period. Compared with chirped FBG with complexdifferential stretching or hearting, it is more advantageous in that it has simplestructure and small footprint, and that it is easier to be sealed.In this paper, a novel design method of tunable dispersion-slopecompensator based on SFBG is presented. According to universal type ofcubic group delay curve, concrete design method based on equivalent-chirpmethod has been given to produce desirable SFBG. Especially, analyticalexpression solution to the simplest type of cubic group delay curve has beengiven. For some more complicated group delay curve, the solution can begained by some numerical methods in the same way. In some situations, thesolution of SFBG structure must be adjusted by reconstructionalgorithm.Furthermore in this paper, fabrication results of SFBG based onabove-mentioned design method are given. These results not only validate thecorrectness of the design method, but also fulfill the desirable requirements.At the same time, some conclusions of the results are helpful to some otherresearches about SFBG.更多还原