Opt Lett. 2018 Sep 1;43(17):4200-4203. doi: 10.1364/OL.43.004200.
A refractive index sensor based on an in-line Fabry-Perot interferometer is proposed and experimentally demonstrated. Two lasers are combined and injected into the sensor head. The power responses of two wavelengths are measured by a dual-channel optical power meter simultaneously. The two reflected power signals distribute along an ellipse. The refractive index of the liquid is calculated from the half length of the longer axes of the fitted ellipse. The refractive index sensing system is demonstrated to measure the refractive index of the salt solutions with different concentrations. The demodulated results matched well with the refractive index measured by the Abbe refractometer, and a resolution of 0.0017 was obtained. Since the temperature is eliminated during the ellipse fitting, the measuring result is insensitive to the temperature fluctuation. The proposed refractive index sensing sensor has outstanding advantages, such as low demodulation cost, simple fabrication, easy cleaning, and good mechanical strength, and will be of importance in biological detection, chemical analysis, and water pollution monitoring.
提出并实验验证了一种基于光纤法布里-珀罗干涉仪的折射率传感器。两个激光器被组合并注入传感器头部。双通道光功率计同时测量两个波长的功率响应。两个反射功率信号分布在一个椭圆上。通过拟合椭圆的长半轴的半长度来计算液体的折射率。折射率传感系统被证明可以测量不同浓度的盐溶液的折射率。解调结果与阿贝折射仪测量的折射率吻合良好，分辨率达到 0.0017。由于在椭圆拟合过程中消除了温度的影响，因此测量结果对温度波动不敏感。所提出的折射率传感传感器具有成本低、制造简单、易于清洁、机械强度好等突出优点，在生物检测、化学分析和水污染监测等领域具有重要意义。
