新型的分段结构光纤倏逝波传感器

Novel Segmented Structure Optic Fiber Evanescent Wave Sensor

提出一种基于倏逝波吸收原理的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一个界面上被反复地激发。分析不同结构、纤芯直径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,在传感直径相同的条件下,传感长度为5cm分段结构光纤倏逝波传感器的灵敏度为0.0135L/mmol,优于传感长度为6cm的传统的单一直形传感器的灵敏度0.0102L/mmol。分段结构光纤倏逝波传感器能有效地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,在物质光谱检测方面有着潜在的应用。

Based on evanescent wave absorbed theory,a segmented structure optic fiber sensor is proposed.The waveguide models of the segmented structure and straight are simulated and analyzed by using beam propagation method（BPM）,which shows the high-order modes are excited repeatedly at the first transition of the each segmented region in the segmented structure.The effects of the different structures,core diameters and concentrations of solution on the sensitivity of the sensors are investigated,and the sensitivity is tested by using the different concentrations of the methylene blue solutions.The experimental results show that,with the fixed core diameters,the sensing region length of segmented structure sensors is 5 cm,which is shorter than that of the conventional single straight sensor 6 cm. However, the sensitivity of segmented structure sensors is0.0135 L/mmol,which is higher than that of conventional single straight sensor 0.0102 L/mmol.The segmented structure evanescent wave sensor can effectively stimulate the fiber low-order modes to the high-order modes,and than the sensitivity is enhanced.The results are consistent with theoretical models and simulation analysis.The proposed sensor not only has a high sensitivity,but it is robust due to the larger core diameters and shorter length of the segmented region,which is suitable for materials spectrum measurements.