一种双段多层长周期光纤光栅光谱特性研究

长周期光纤光栅(LPFG)传感器具有非常广泛的应用价值,而有效解决物理量交叉敏感问题是其实用化的关键。基于LPFG对包层外介质折射率和厚度的敏感性,提出一种双段多层折射率横向分布结构的新型LPFG传感器的设计,并利用耦合模理论和传输矩阵方法分析了镀膜材料折射率、膜层厚度和镀层长度对新型LPFG传感器光谱特性的影响。软件仿真结果证明,这种LPFG由于结构设计上的特殊性,将使LPFG的谐振峰发生分裂,即一个透射峰分裂为两个。由于两个分裂峰对应力和温度的灵敏度不同,利用该结构的LPFG作为传感器,可以实现温度、应力等物理量的同步测量,从而解决LPFG传感器的交叉敏感问题。

Research on Optical-Spectral Characteristics of Two-Section and Multi-Layer Long-Period Fiber Grating

Long-period fiber grating (LPFG) has a wide range of potential applications. But it is necessary to solve the cross sensitive problems of different physical quantities effectively before its practical application. Based on the sensibility of LPFG to the thickness and refractive index of cladding material, a new-type LPFG sensor composed of two-section multilayer transversely distributed refractive index is proposed. The influences of refractive index, thickness and length of the coating layer on the spectral characteristics of the new-type LPFG are analyzed by using coupling mode theory and transfer matrix method. The simulation results show that the resonant band splits due to the particularity of the LPFG structure. It can be concluded that this LPFG design can solve the cross sensitive problem and then can realize synchronous measurement of temperature, strain and other physical quantities.