基于周期压力单模光纤长周期光栅的折射率传感特性研究

利用交替放置的两个相同周期性刻槽板,对放置于套管中的单模裸纤和待测媒质施力,形成了具有复合光波导结构的长周期光纤光栅(LPFG)。实验研究了不同折射率待测媒质对LPFG传输谱的影响。结果表明:复合波导光栅的光谱呈现双谐振峰现象,且中心谐振波长随待测媒质折射率增大向短波长方向移动;包层模阶次越高,其中心谐振波长移动量越大。当折射率从1.33变化到1.43时,LP14包层模的中心谐振波长变化了7.2nm,所对应的传感器折射率灵敏度约为2.78×10-4 RIU。

Investigation on refractive index sensing characteristics of pressure-induced long-period fiber grating written in a single-mode fiber

The pressure-induced long period fiber grating(LPFG) is formed by pressing the composite waveguide,which consists of a single-mode fiber with a portion of its coating stripped away,and the medium to be measured within a teflon-cannula from double sides with two identical periodically grooved plates.The influence of medium with different refractive indices on the transmission spectrum of the LPFG is investigated experimentally.The results show that the spectrum of the composite waveguide-based grating presents dual-peak resonance,and the central resonant wavelength shifts towards short wavelength as refractive index increases.The higher order of cladding mode is,the greater of the central resonant wavelength movement of the LPFG will be.The central resonant wavelength of the LP14 cladding mode exhibits a total blue shift of 7.2 nm,which corresponds to a sensitivity of 2.78×10-4 RIU,when refractive index changes from 1.33 to 1.434.