超短光纤光栅刻写及其切趾方法研究

Research on the inscription and apodization method of ultra short fiber Bragg grating

常用的光纤光栅的栅区长度为厘米量级,影响了其在非均匀物理场测量的应用。将光栅的栅区长度压缩到百微米以下,可以解决非均匀场的测量和光谱变形的问题。本文通过设置狭缝光阑以及调节掩模板与光纤之间的距离,实现了光栅有效长度的大幅度缩短,刻写出长度分别为0.1 mm、0.2 mm、0.5 mm,3 dB带宽为7.9 nm、4.2 nm、2.1 nm,反射率为5%、10%、30%的超短光栅,通过调节掩模板与光纤的距离,实现了栅区长度为0.05 mm,3 dB带宽为14 nm的超短光纤光栅的刻写。本实验采用单缝衍射的方法来控制光束强度的分布,从而对光栅进行切趾,此方法可以实现边模抑制比大于30 dB、长度为0.5 mm的光栅刻写。

The length of ordinary uniform fiber gratings is gauged in the order of centimeters,which restricts the spatial resolution of the measurement,and produces spectral distortion for the measurement of non-uniform fields,which affects the measurement accuracy.The length of the gate region of the ultra-short FBG is measured in the order of 10~100μm,which can solve the problems of non-uniform field measurement and spectral distortion.In this paper,the effective length of the grating is greatly shortened by setting the slit diaphragm and adjusting the distance between the mask and the optical fiber,and the ultra short gratings are produced with a length of 0.1 mm,0.2 mm,0.5 mm,and a 3 dB bandwidth of 7.9 nm,4.2 nm,2.1 nm,and a reflectivity of 5%,10%,30%.By adjusting the distance between the mask and the fiber,ultra-short fiber gratings with a gate length of 0.05 mm and a 3 dB bandwidth of 14 nm can be written.In order to suppress the side mode suppression ratio of ultra-short fiber gratings,the grating apodization was performed using a single slit diffraction modulated beam intensity distribution,and the writing of a 0.5 mm grating with a greater than 30 dB side mode suppression ratio is realized.