基于光纤激光器时域特性的液体浓度传感器

A Sensor for Measuring Solution Concentration Based on Fiber Laser′s Time Regime

报道了一种基于掺铒光纤激光器时域特性的新型液体浓度传感系统.用光纤环反射镜和光纤Bragg光栅(FBG)构成F-P线形腔.谐振腔内插入长周期光纤光栅(LPG) ,FBG的反射波长落在LPG的透射峰左侧.把LPG浸泡在待测液体中,利用LPG对环境折射率的敏感特性,即环境液体浓度的改变引起折射率改变,这将引起LPG透射谱平移,从而使腔内损耗发生变化,影响了激光器的瞬态时域特性.通过测量激光激射的延迟时间可以获得被测液体的浓度.在最佳工作条件下,系统的浓度分辨率为0 .015 %.

A novel fiber sensor for measuring liquid concentration is reported, which is based on the time regime of a Er-doped fiber laser. A Sagnac fiber loop and a FBG that also acts as the sensing element form the linear fiber laser cavity. The FBG＇s reflected wavelength is set to locate at the left of LPG＇s transmission spectrum with inserting a LPG into the laser cavity. LPG＇s transmission spectrum is sensitive with the refractive index, which means the refractive index changes with the change of liquid concentration. By dipping a LPG into the pending liquid, the transmission loss increases with the refractive index-induced shift of the LPG＇s transmission spectrum, which in turn modifies the laser build-up time. The liquid concentration can be obtained by measuring the laser build-up time. In the best experiment condition, the resolution of this sensor is 0. 015%.