对光纤布拉格光栅法布里-珀罗腔纵模间隔问题的研究

对光纤布拉格光栅(FBG)法布里-珀罗(F-P)腔的透射特性进行了深入分析，指出了FBG F-P腔透射谱中纵模位置的影响因素，讨论了与普通F-P腔的联系和区别.应用光栅的有效镜面模型对FBG反射主瓣内反射系数的相位因子进行线性模拟，定义了FBG有效长度的概念并得出其表达式.提出将FBG的有效长度纳入到FBG F-P腔的等效腔长中，用等效腔长来计算FBG F-P腔中的纵模间隔.数值仿真和实验结果都表明，用等效腔长计算所得的纵模间隔与实际的FBG F-P腔中的纵模间隔符合很好，误差极小. 关键词： 光纤布拉格光栅 法布里-珀罗腔 纵模间隔 有效镜面模型

A study on the interval between longitudinal modes of Fabry-Perot cavity composed of fiber Bragg gratings

The characteristics of transmission spectrum of the Fabry-Perot (F-P) cavity composed of two fiber Bragg gratings (FBG) are analyzed detailedly in this paper. The influencing factors of the position of the longitudinal mode are pointedout. The relationship and difference between the FBG F-P cavity and normal F-P cavity are discussed. The phase factor of the amplitude reflection coefficient in the range of the FBG main lobe is simulated linearly using the effective mirror surface model. The effective length of the FBG is defined and the expression of the effective length is obtained. Furthermore， the effective length of the FBG is brought into the equivalent cavity length of the FBG F-P cavity. The interval between longitudinal modes of the FBG F-P cavity is calculated using the equivalent cavity length. Both the numerical simulation and experimental results show that the interval calculated using the equivalent cavity length accords well with the true interval between longitudinal modes of the FBG F-P cavity.