基于光纤F-P干涉波长的溶液浓度测量系统研究

Solution Concentration Measurement System Based on Fiber Fabry-Perot Interference Wavelength

为了消除光源强度波动对测量结果的影响 ,根据溶液浓度与其折射率的关系和光纤法布里 -珀罗 (F- P)干涉仪透射光谱中心波长与干涉仪腔内介质折射率之间的关系 ,利用其透射光谱的中心波长进行透明溶液浓度的精确测量 ,开发出测量实验系统。采用可调光学滤波器对传感信号进行采集。对浓度为 5 %～ 80 %的酒精进行了实际测量实验 ,浓度最大测量偏差为 0 .0 0 3%。该系统具有如下特点 :1)与 CCD测量技术相比 ,采用法布里 -珀罗干涉系统透射光谱的波长信号进行溶液浓度测量 ,可实现连续大范围、高精度测量 ;2 )消除了光源波动对测量结果的影响 ,可实现连续高精度测量 ,且测量范围宽 ;3)直接利用光电探测器 PIN进行传感信号的检测 ,使系统计算简单 ;4 )便于实现分布式遥测系统 ;5 )直接拟合出 F- P干涉波长与溶液浓度之间的关系 ,使其更适合于工程实际的应用。

To essentially eliminate the measurement errors arisen from light source power fluctuation, a measurement method of solution concentration was proposed. The method is based on the relationship between transmission optical spectrum central wavelength of fiber Fabry-Perot (FFP) interferometer and the refractive index of medium in the cavity, as well as the relationship between solution refractive index and its concentration. Such a measurement system was developed. A tunable fiber optical Fabry-Perot (F-P) filter was used to collect the sensing data. Different concentrations of a set of alcohol solution, with the concentration being from 5% to 80%, were measured experimentally. The maximum absolute measurement bias is no more than 0.003%. This measurement system possesses following advantages: 1) It can be used to precisely measure the resolution concentration with a large dynamic span, comparing with a system comprises CCD (charge coupled device) camera; 2) it is immune to the fluctuation of light source, and thus a wide range precise and continuous measurement can be achieved; 3) The test system is largely simplified through employing a PIN photodetector to collect the sensing signal directly; 4) It is easy to fulfill a distributed remote measurement; 5) The proposed system is quite suitable for field applications because the concentration of the measurand can be elicited from the light wavelength.