具有温度自补偿的级联光栅传感特性研究

Research on sensing technology of cascade grating with temperature compensation

通过对长周期光纤光栅(LPFG)与Bragg光纤光栅(FBG)级联结构进行研究,利用传输矩阵法详细分析了正反向芯模与包层模之间的耦合机理,得到结构参数改变对级联光栅传输谱的影响规律,并对其温度和折射率传感特性进行探讨.实验室成功制备了LPFG-FBG级联光栅,观察到明显的耦合双峰现象.理论分析和实验结果表明,双峰中由FBG芯模与包层模耦合形成的谐振峰对折射率不敏感,而由LPFG包层模与FBG芯模前后向耦合形成的谐振峰对折射率敏感,且二者对温度变化具有相同响应.利用此特性,可实现温度与折射率的同时测量,且能消除温度变化的影响,实现温度自补偿的折射率传感.

By studying the cascade structure of long-period fiber grating (LPFG) and Bragg fiber grating (FBG),the coupling mechanism between forward and backward core modes and cladding modes is analyzed in detail by transfer matrix method.The influence of structural parameters on the transmission spectrum of the cascade grating is obtained,and the temperature and refractive index sensing characteristics are discussed.And the cascade grating of LPFG-FBG is constructed successfully in this experiment.The results show that,the resonant peak formed by the coupling of the FBG mandrel and the cladding mode in the bimodality is insensitive to the refractive index,while the resonant peaks formed by the coupling between LPFG cladding mode and FBG core mode are sensitive to refractive index,and both of them have the same response to temperature variation.In this way,simultaneous measurement of temperature and refractive index can be realized,the influence of changing temperature can be eliminated,and the refractive index sensing of temperature self-compensation can be implemented.