基于反射谱重构的光纤光栅再生过程研究

Study on Regeneration Process of Fiber Grating Based on Reflection Spectrum Reconstruction

提出一种新的光纤光栅反射谱重构方法,通过再生过程中反射谱的重构,对再生规律进行总结。基于耦合模理论,推导了光栅的主要参数,包括栅区长度、周期及折射率调制深度平均值的表达式。结合传输矩阵法中的特征参数,即光栅有效折射率和折射率调制深度对反射谱的影响规律,提出重构方法,并用相关系数进行了评价。进行光纤光栅再生实验记录反射谱的演变,重构出光栅参数变化。研究发现:再生过程中折射率呈幂指数函数形式,指数随退火时间增长而减小。据有效折射率退火时的变化,分析光栅再生时所产生的不同程度内应力的释放,引起有效折射率的周期性调制。

In this paper,a new method of reconstructing the reflection spectrum of fiber grating was proposed.The reconstruction law was summarized by reconstructing the reflection spectrum in the process of regeneration.Based on the coupled-mode theory,the expressions of the main parameters of the fiber grating,i.e.,the grating length,the period and the depth of the refractive index modulation,were derived.Combined with the characteristic parameters in transfer matrix,i.e the influence laws of effective refractivity and refractive index modulation depth,a reconstrution method was proposed and evaluated with the spectral correlation coefficient.The regeneration experiment of fiber grating was carried out.The evolution of reflection spectrum during regeneration process was recorded,and the change of grating parameters was reconstructed.It is found that in the process of grating regeneration,the refractive index distribution is in the form of exponential function,and the power exponent decreases with the increase of annealing time.According to the change of effective refractive index of grating during annealing,it is analyzed that the release of internal stress in different degree when the grating is regenerated,and then the periodic modulation of effective refractive index is caused.