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提出一种基于倏逝波吸收原理的高灵敏度分段结构光纤倏逝波传感器。运用光束传播法(BPM)对分段和直形波导模型进行数值模拟,分段波导中高阶模在每次分段的第1个界面上被反复的激发和吸收。分析不同结构和溶液浓度对传感器灵敏度的影响,通过化学腐蚀方法制备出不同结构参数的倏逝波传感器,并用不同浓度亚甲基蓝溶液对传感器的灵敏度特性进行实验验证。实验结果表明,在传感直径相同和分段结构传感器的传感长度3cm短于传统的单一的直形传感器传感长度5cm的条件下,分段结构传感器的灵敏度是0.038 0L/g,优于直形传感器的灵敏度0.026 2L/g。分段结构光纤倏逝波传感器能有效激发光纤中低阶模到高阶模的转变,从而提高传感器的灵敏度。实验结果与模拟和理论结果相符。因此,分段结构光纤倏逝波传感器相对于传统的单一的直形传感器不仅具有较高的灵敏度,且机械强度较高。
A novel high-sensitivity optical fiber evanescent wave sensor based on evanescent wave absorption principle is proposed. The beam propagation method (BPM) was used to numerically simulate the segmented and straight waveguide models. The high-order modes in the segmented waveguide were repeatedly excited and absorbed at the first interface of each section. The effects of different structures and solution concentrations on the sensitivity of the sensor were analyzed. Evanescent sensors with different structural parameters were prepared by chemical etching method. The sensitivity of the sensor was experimentally verified by different concentrations of methylene blue solution. The experimental results show that the sensitivity of the sectionalized sensor is 0.038 0L / g under the condition that the sensing length of 3cm with the same sensing diameter and the sectional structure sensor is shorter than that of the conventional single straight sensing sensor with a sensing length of 5cm, which is better than Sensitivity of straight sensor 0.026 2L / g. The segmented optical fiber evanescent wave sensor can effectively stimulate the transition from low-order mode to high-order mode in the fiber to improve the sensitivity of the sensor. The experimental results are in agreement with the simulation and theoretical results. Therefore, the segmented optical fiber evanescent wave sensor not only has higher sensitivity and higher mechanical strength than the traditional single straight sensor.