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采用优化改进的CO_2激光器制备了两种不同刻槽深度的长周期光纤光栅(LPFG),实验研究了光纤光栅刻槽区结构对应变传感特性的影响。研究结果表明:单侧周期性刻槽会在光纤光栅表面形成应力集中区,在轴向应变作用下发生微弯形成波状型结构,从而极大地提高了其应变响应灵敏度,深刻槽光纤透射谱的谐振波长线性漂移达到-10.96 nm,应变灵敏度达到-19.37 pm/με,且测量误差小。利用有限元分析软件ANSYS对刻槽型光纤光栅进行网格建模和模态仿真分析,得到其刻槽结构区的应变分布图。结果表明,深刻槽型光纤光栅随着应变增加,轴向微弯形变量增大,从而激发高阶包层模的耦合,提高了应变灵敏度响应。
Two kinds of long period fiber grating (LPFG) with different groove depths were fabricated by the optimized and improved CO_2 laser. The influence of groove grating structure on the strain sensing property was studied experimentally. The results show that the one-side periodic groove will form a stress concentration zone on the surface of the fiber grating, and the wavy-shaped structure is formed by the micro-bending under axial strain, thereby greatly improving the sensitivity of strain response. The transmission spectrum of deep groove fiber The resonant wavelength linear drift reaches -10.96 nm, the strain sensitivity reaches -19.37 pm / με, and the measurement error is small. The finite element analysis software ANSYS was used to mesh and simulate the groove grating fiber grating. The strain distribution in the groove structure was obtained. The results show that the deep groove fiber gratings increase the axial micro-bending deformation with the increase of strain, so as to stimulate the coupling of high-order cladding modes and improve the strain sensitivity response.