全光纤粗锥MZ级联PCF-FP结构双参数特性研究

为了在测量NaCl溶液浓度的同时实现对温度的监测，提出了一种基于马赫-曾德干涉仪（Mach-Zehnder Interferometer，MZI）级联法布里-珀罗干涉仪（Fabry-Perot Interferometer，FPI）的干涉型传感器。在单模光纤上通过熔融放电制作出一对腰锥直径155 m、间隔1.5 cm的MZI，其对比度为10 dB、周期29.85 nm；在MZI尾纤的一端与光子晶体光纤（Photonic Crystal Fiber，PCF）相对熔接并在距熔接点176 m处将PCF切平，形成对比度为8 dB、周期为5.71 nm的FPI。实验选取1 535~1 555 nm波段MZI和FPI的干涉波谷特征波长，在0~150℃的温度和0%~24%的NaCl溶液浓度变化范围内测得MZI的温度和折射率灵敏度分别为50 pm/℃和9.97 nm/RIU，线性度均大于0.97；而FPI的波谷特征波长对折射率不敏感，温度灵敏度约为8.3 pm/℃，线性度为0.98。最后，通过构建温度-浓度函数关系矩阵得出了对温度和NaCl溶液浓度的灵敏度矩阵。该干涉型传感器对温度和NaCl溶液浓度表现出良好的灵敏度和线性度，可实现上述双参数的同时测量。

Dual-parameter characterization based on all-fiber waist-enlarged-bitapers MZ cascaded PCF-FP

In order to meet the requirement of monitoring temperature change during the NaCl solution concentration measurement, an interferometric sensor based on Mach-Zehnder interferometer(MZI) cascaded Fabry-Perot interferometer(FPI) was proposed. The MZI was prepared by melting and splicing a single mode fiber to form a pair of tapers structure with diameter of 155 m at the waist an interval of 1.5 cm and the contrast and period of the MZI was 10 dB and 29.85 nm, respectively; Then a photonic crystal fiber (PCF) was spliced to one end of the MZI, cleaving the PCF at a distance of a 176 m from the splicing position, which a FPI was formed with contrast and period of 8 dB and 5.71 nm, respectively. By selecting the characteristic wavelength shifts of MZI and FPI interference dips in the range of 1 535-1 555 nm, in the temperature range of 30-150℃ and NaCl solution concentration range of 0%-24%, the temperature and refractive index sensitivities were 50 pm/℃ and 9.97 nm/RIU, respectively. The linearities were both greater than 0.97; While the interference dip of FPI was insensitive to the refractive index, and its sensitivity of temperature and linearity was 8.3 pm/℃ and 0.98, respectively. Finally, the sensitivity matrix for temperature and NaCl concentration was calculated by constructing the temperature-NaCl concentration function matrix. The interferometric sensor has good sensitivity and linearity to temperature and concentration of NaCl solution, which can realize the simultaneous measurement of the mentioned parameters.