基于双光栅级联结构的温度及浓度传感特性测试

Measurement of temperature and concentration sensing characteristics based on dual-grating cascade structure

研究了长周期光纤光栅(LPFG)级联布拉格光纤光栅(FBG)结构的温度及浓度传感特性。利用飞秒激光直写制作LPFG并级联FBG,且FBG波谷位于1 551.9 nm,LPFG波谷位置为1 560.5 nm。在30~50℃温度变化范围内对传感器温度特性进行测试,并在25℃超净环境下对浓度为3%~30%的葡萄糖溶液进行敏感性测试。实验结果表明:升温过程FBG中心波长发生红移,灵敏度26.36 pm/℃,线性度0.950 8;LPFG中心波长发生蓝移,灵敏度-24.55 pm/℃,线性度0.914 2。降温过程FBG中心波长发生蓝移,灵敏度25.00 pm/℃,线性度0.945 8;LPFG中心波长发生红移,灵敏度为-21.82 pm/℃,线性度0.921 2。FBG对浓度变化不敏感,当浓度由3%增至30%时,LPFG中心波长发生蓝移,灵敏度196.36 pm,线性度0.956 5。结果表明该光纤传感器灵敏度高,线性度好,可以同时动态实现温度和浓度的测量。

A dual-grating cascade structure based on long period fiber grating （LPFG） cascaded with fiber Bragg grating （FBG） for temperature and concentration measurement has been proposed. The proposed fiber sensor was cascaded by LPFG micromachined by the femtosecond laser and FBG, and the transmission spectrum has two valleys, namely FBG valley at 1 551.9 nm and LPFG valley at 1 560.5 nm. The temperature and concentration sensing characteristics of the proposed sensor were measured at 30-50℃ and 3%-30%, respectively. The experimental results show that when the temperature rises, the FBG shows red shift with increasing wavelength, the sensitivity is 26.36 pm/℃, and the linearity is 0.950 8; on the contrast, the LPFG shows blue shift with decreasing wavelength, the sensitivity is -24.55 pm/℃, and the linearity is 0.914 2. When the temperature falls, the FBG shows blue shift with decreasing wavelength, the sensitivity is 25.00 pm/℃, and the linearity is 0.945 8; the LPFG shows red shift with increasing wavelength, the sensitivity is -21.82 pm/℃, and the linearity is 0.921 2. The FBG is not sensitive to the concentration variation. When the glucose concentration rises from 3% to 30%, the LPFG shows blue shift with decreasing wavelength, the sensitivity is 196.36 pm, and the linearity is 0.956 5. The proposed sensor has high sensitivity and good linearity for dual-parameter measurements.