同时测量折射率和温度的光纤传感器

Optical fiber sensor for simultaneous measurement of refractive-index and temperature

为了实现折射率(RI)和温度的同时测量,提出了一种双长周期光纤光栅(LPG)结构的光纤传感器.该传感器由两段LPG组成,两段LPG所激发的包层模阶数不同,且两段LPG的包层直径也不同.理论分析了该传感器实现折射率和温度同时测量的原理,两段LPG对折射率具有较大差异的灵敏度,而温度灵敏度也略有不同,利用灵敏度矩阵可以同时得到折射率和温度的变化.实验中,采用两个不同的周期使得两个LPG分别激发不同阶的包层模,利用化学腐蚀方法使激发高阶模的LPG包层直径减小,利用不同折射率的液体作为样本进行实验测量.实验结果表明,该传感器能实现折射率和温度的同时测量,并具有高灵敏度和好的线性度.

An optical fiber sensor based on long-period gratings （LPGs） was proposed for simultaneous measurement of refractive-index （RI） and temperature. The sensor consists of two LPG sections exciting different order cladding modes and having different cladding diameters. The principle of simultaneous measurement was theoretically analyzed. The two LPGs have different RI sensitivities but similar temperature sensitivities, which construct the sensitivity matrix. The variation of RI and temperature can be deduced by the sensitivity matrix. Two different grating-periods were used to enable the LPGs exciting different order cladding modes and a chemically wet etching was processed on one LPG section to decrease the cladding diameter. The sensor was measured in liquid with different RI. Experimental results show that the LPG-based sensor can discriminate between RI and temperature and has a good performance in terms of sensitivity and linearity.