保偏光纤光栅应变传感器的研究

Study on polarization maintaining fiber Bragg grating strain sensor

  • 摘要: 针对光纤布拉格光栅(FBG)温度和应变的交叉敏感问题,设计了一种带熔点保偏光纤光栅(PMFBG)结构。该结构通过将2段保偏光纤带加大推进量熔接,形成中间凸起结构,然后在熔点位置写入光栅。文中首先采用熊猫保偏光纤设计制作了该结构,并搭建实验装置测试其在(0~2)N轴向应力作用下的反射光谱,发现PMFBG快轴和慢轴的反射谱均分裂成2个峰值,随着轴向应力的增加,反射谱整体产生红移,同时分裂的2个峰值强度的比值单调减小,且不受温度的影响。随后,采用有限元法分析了该结构的轴向应变分布,并基于传输矩阵法仿真分析了该PMFBG反射光谱随应力的变化特性,仿真与实验结果的一致性较好。证实可利用PMFBG反射光谱的峰值之比消除轴向应变与温度的交叉敏感性,实现轴向应变的测量。

     

    Abstract: The special polarization maintaining fiber Bragg grating(PMFBG) with fusion spliced joint was proposed to overcome the cross-sensitivity of the temperature and the axial stain. The structure introduced a bulge by splicing the two fibers, then the FBG was inscribed symmetrically in the middle of the fusion spliced joint. The special PMFBG was manufactured by panda polarization-maintaining fiber and the reflection spectra was measured under 0~2N axial stress. It is found that the reflection spectra of the fast and slow axis split to two peaks respectively and shift towards the longer wavelength side with increasing axial stress, the ratio of the peaks decreases at the same time and is not affected by the temperature. Moreover, the axial strain character of the structure was simulated by the finite element method, and the reflection spectra of the PMFBG were calculated by the transfer matrix method. The simulation and experimental results are in good agreement, verifying that the peak ratio of the PMFBG reflection spectrum can be used to eliminate the cross-sensitivity of axial strain and temperature, and the measurement of axial strain can be realized.

     

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