中文摘要：

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。

英文摘要：

A high sensitivity segmented structure optic fiber sensor is proposed, which is based on evanes- cent wave absorbed theory. The modes of the segmented structure and straight waveguide are simulated and analyzed by using beam propagation method （BPM）, which shows that the high-order modes are ex- cited and absorbed repeatedly at the first transition of each segmented region in the segmented structure. The effects of the different structures, the core diameters and the concentration of solution on the sensi- tivity of the sensors are investigated,and the sensitivities are tested by using different concentrations of the methylene blue solution. The experimental results show that with the fixed core diameters,the sensi- tivity of segmented structure sensors is 0. 038 0 Ijg, which is higher than that of the conventional single straight sensor （0. 026 2 L/g）,while the sensing region length of the former （1 cm） are shorter than that of the latter （5 cm）. The segmented structure evanescent wave sensor can effectively stimulate the fiber low-order modes to the high-order modes, the sensitivity will be higher. The result is consistent with theoretical models and simulation analysis. The proposed sensor not only has a high sensitivity, but also is robust due to the larger core diameters and shorter length of the segmented region,which is suit- able for materials spectrum measurements.