Study on the sensing characteristics of a local micro-structured long period fiber grating

A simple and effective method employing a local micro-structured long period fiber grating （LMS-LPFG） for the simultaneous measurement of temperature and refractive index is proposed and investigated experimentally. The LMS-LPFG is formed by using the partial etching technique with hydrofluoric （HF） acid in a standard LPFG, in which there are discontinuities in the effective refractive index of cladding modes. Similar to the phase shift theory, a narrow passband and two stopbands are formed. The temperature and the surrounding refractive index （SRI） characteristics of the two stopbands and passband are studied. The temperature sensitivities of the two stopbands and passband are 0.05 nm/℃ approximately. The SRI sensitivity ofpassband （-61.56 nm/RIU） is bigger than that of the two stopbands （-35.62 nm/RIU）. Thus, with the sensitive matrix, we can simultaneously measure the changes of temperature and refractive index.     

一种新型光纤光栅温度传感特性的实验研究

研制出一种具有微结构缺陷的新型光纤光栅,并对其温度特性进行了实验研究。该光栅是利用不同浓度的氢氟酸溶液对光纤布拉格光栅进行选择性刻蚀得到的,刻蚀区域改变了光纤的局部有效折射率,引入附加相移从而形成两个谐振峰。实验研究结果表明该新型光栅具有不同的温度灵敏系数,在20℃~90℃的温度范围内,随温度升高两谐振峰波长分别向长波方向移动了0.8127 nm和0.7329 nm,其温度灵敏系数分别为0.01161 nm/℃和0.01047 nm/℃,线性拟合度分别为0.991和0.998,新型光纤光栅两谐振峰随温度的变化呈现良好的线性关系。