基于薄包层极大倾角光纤光栅的灵敏度增强型振动传感器

Sensitivity-enhanced Vibration Sensor Based on Thin-cladding Excessively Tilted Fiber Gratings

提出了一种薄包层极大倾角光纤光栅悬臂梁振动传感器,采用基于标准单模光纤的极大倾角光纤光栅,从理论上分析包层半径的减小对波导色散因子、包层模的有效折射率、轴向应变灵敏度因子、轴向应变灵敏度及模式阶数的影响,并进行数值仿真,为其振动传感增敏方法提供理论依据。然后使用氢氟酸腐蚀光纤包层,构成不同直径的极大倾角光纤光栅并进行相关振动传感实验。实验结果表明:在40~200 Hz的频率范围内,随着包层直径的减小,极大倾角光纤光栅振动传感器在C波段的同阶和不同阶TE/TM模加速度灵敏度逐渐增大,且两者之间具有较好的线性关系;其中,同阶TE和TM模的最大加速度灵敏度分别可达到100.46 mV/g与88.68 mV/g,相对于标准直径极大倾角光纤光栅振动传感器分别提高了1.36倍、1.53倍;不同阶TE和TM模的最大加速度灵敏度可达到159.35 mV/g与133.37 mV/g,分别提高了2.15倍、2.31倍。

A thin-cladding Excessively Tilted Fiber Gratings(ExTFG)cantilever beam vibration sensor is reported in this paper.Using the ExTFG written in the standard single-mode fiber,the effects of the decrease of the fiber cladding radius on the dispersion factor of the waveguide,the effective refractive index of the cladding mode,the axial strain sensitivity factor,the axial strain sensitivity and the mode order are theoretically analyzed,and the corresponding numerical simulations are performed,which provide the theoretical foundation for the enhancement method of vibration measuring sensitivity.And then,hydrofluoric acid is used to etch the fiber cladding to fabricate ExTFGs with different diameters and the related vibration sensing experiments are conducted.The results show that in the vibration frequency range of 40~200 Hz,with the decrease of cladding diameter,the acceleration sensitivity of ExTFG vibration sensor in C band of the same order and different order TE/TM mode increases gradually,and there is a good linear relationship between them.The maximum acceleration sensitivity of the TE and TM mode with the same-order cladding mode is 100.46 mV/g and 88.68 mV/g,respectively,which is increased by 1.36 times and 1.53 times,respectively,as compared with the standard diameter one.And the maximum acceleration sensitivity of those with different-order cladding modes can reach 159.35 mV/g and 133.37 mV/g,respectively,which is increased by 2.15 times and 2.31 times.