【作者】 张森；

【导师】 荆振国；

【作者基本信息】 大连理工大学 ， 电子信息（专业学位）， 2023， 硕士

【摘要】 空芯光纤(Hollow Core Fiber,HCF)作为结构简单的反谐振(Antiresonant,AR)光纤,具有优良的物理性能、良好的机械稳定性和优异的环境适应性,成为制备基于光纤反谐振波导结构的光纤传感器的重要器件,引起光纤传感器研究者的特别关注。HCF与全内反射型光纤不同,全内反射型光纤的纤芯折射率高于包层折射率,光线的传输满足全反射原理。而HCF具有空气芯和二氧化硅包层,纤芯折射率低于包层折射率,传输光线会泄露到包层中,基于HCF的光纤传感器具有多种传感机理。空芯光纤的反谐振反射效应是以二氧化硅包层为谐振腔,对温度、应力、振动等环境参量的变化特别敏感。大芯径空芯光纤中由反谐振反射效应引导的透射光谱品质因子较低,在传感测量中灵敏度和精准度受到一定程度的限制。本论文主要研究了大芯径空芯光纤中的反谐振反射效应,提出了一种基于空心光纤的反谐振波导结构光纤传感器,利用四分之一节距大芯径渐变折射率多模光纤(Graded-Index Multi-mode Fiber,GIMF)对耦合到空芯光纤内的光模场进行精确控制,实现空芯光纤反谐振波导结构的高品质因数传输光谱。具有高品质因子特点的传输光谱,可进行高精度高灵敏度的传感测量。论文并对传感器在声传感和温度传感测量方面进行实验研究。论文的主要工作概括如下:设计了单模光纤-渐变折射率多模光纤-空芯光纤-渐变折射率多模光纤-单模光纤(SMF-GIMF1-HCF-GIMF2-SMF,SGHGS)结构的反谐振反射光纤传感器,对传感器的设计原理和制备工艺进行详细的研究。首先研究了内径为40μm和80μm两种HCF的单模光纤-空芯光纤-单模光纤(SMF-HCF-SMF,SHS)结构光纤传感器的光谱特性,其中80μm大芯径HCF的透射光谱对比度受到芯径的限制。其次利用数值仿真软件对SHS结构中光的传输分布进行了研究分析。然后从理论上推导了提高大芯径空芯光纤中反谐振反射效应引导的光谱对比度的方法,利用渐变折射率多模光纤(GIMF)的光线以正弦振荡形式传输的特点,对耦合到空芯光纤的光模场进行精确控制,设计了SGHGS结构的反谐振反射光纤传感器。最后研究了该结构传感器的制备工艺,制备出的反谐振波导结构光纤传感器的透射光谱对比度相比同参数SHS结构光纤传感器的透射光谱对比度提高了3倍左右,提高了传感器光谱的品质因子,谐振峰也更加尖锐。对提出的SGHGS结构反谐振反射光纤传感器在传感应用方面进行了进一步的探索研究。搭建了声传感实验系统,利用单波长强度解调的方式对传感器进行了声传感实验,结果显示提出的SGHGS结构反谐振反射光纤传感器在频率为290 Hz、5.6 k Hz、9.2 k Hz时,具有良好的声压响应,声压灵敏度分别为1.189 V/Pa、0.165 V/Pa、0.345 V/Pa,且实验结果具有良好的重复性。然后搭建了温度传感实验系统,利用谱峰追踪的解调方式进行了温度传感实验,SHS结构的传感器在30-130℃范围内的温度响应灵敏度为18.4pm/℃。SGHGS结构的传感器在50-300℃范围内的温度响应灵敏度为23.54 pm/℃。更多还原

【Abstract】 Hollow Core Fiber(HCF),a simple structured Antiresonant(AR)fiber,has excellent physical properties,good mechanical stability and excellent environmental adaptability,and has become an important device for preparing fiber optic sensors based on fiber antiresonant waveguide structure,which has attracted special attention from fiber optic sensor researchers.The core refractive index of total internal reflection fiber is higher than the cladding refractive index,and the light transmission satisfies the principle of total reflection.The HCF has an air core and a silica cladding,and the refractive index of the core is lower than the refractive index of the cladding,so the transmitted light will leak into the cladding.The anti-resonant reflection effect of air-core fiber is based on the silica cladding as a resonant cavity,which is particularly sensitive to changes in environmental parameters such as temperature,stress,and vibration.The quality factor of the transmission spectrum guided by the antiresonant reflection effect in large-core diameter hollow-core fibers is low,which limits the sensitivity and accuracy in sensing measurements to some extent.In this thesis,we focus on the anti-resonant reflection effect in large-core diameter hollow-core fiber,and propose an anti-resonant waveguide structure fiber sensor based on hollow fiber,using quarter-pitch large-core diameter gradient refractive index multi-mode fiber(GIMF)to precisely control the optical mode field coupled into the hollow-core fiber,and realize the anti-resonant waveguide structure of hollow-core fiber.High quality factor transmission spectrum of anti-resonant waveguide structure.The transmission spectrum with high quality factor characteristics enables high precision and high sensitivity sensing measurements.The paper and conducts experimental studies of the sensor in acoustic sensing and temperature sensing measurements.The main work of the thesis is summarized as follows:An antiresonant reflection fiber sensor with single-mode fiber-gradient refractive index multimode fiber-hollow core fiber-gradient refractive index multimode fiber-single mode fiber(SMF-GIMF1-HCF-GIMF2-SMF,SGHGS)structure was designed and the design principle and preparation process of the sensor were investigated in detail.Firstly,the spectral characteristics of the single-mode fiber-hollow-core fiber-single-mode fiber(SMF-HCF-SMF,SHS)structure fiber sensor with two types of HCFs with inner diameters of 40 μm and 80 μm were investigated,in which the transmission spectral contrast of the HCF with large 80 μm core diameter was limited by the core diameter.Next,the transmission distribution of light in the SHS structure was investigated and analyzed by using numerical simulation software.Then a method to improve the spectral contrast guided by the antiresonant reflection effect in the large core diameter hollow-core fiber is theoretically derived,and the antiresonant reflection fiber sensor of the SGHGS structure is designed by using the characteristic that the light of the gradient refractive index multimode fiber(GIMF)is transmitted in the form of sinusoidal oscillation and the optical mode field coupled to the hollow-core fiber is precisely controlled.Finally,the preparation process of this structured sensor is studied,and the transmission spectral contrast of the prepared anti-resonant waveguide structured fiber sensor is improved by about 3 times compared with that of the same parameter SHS structured fiber sensor,which improves the quality factor of the sensor spectrum and sharpens the resonance peak.The application of the proposed anti-resonant reflection fiber optic sensor with SGHGS structure is further explored.An acoustic sensing experiment system was established,and the acoustic sensing experiment was carried out on the sensor by means of single wavelength intensity demodulation.The results show that the proposed anti-resonant reflecting optical fiber sensor with SGHGS structure has good acoustic pressure response at the frequencies of290 Hz,5.6 k Hz and 9.2 k Hz.The sound pressure sensitivity were 1.189 V/Pa,0.165 V/Pa and 0.345 V/Pa,respectively,and the experimental results had good repeatability.Then,a temperature sensing experiment system was built,and a temperature sensing experiment was carried out using the demodulation mode of spectral peak tracking.The temperature response sensitivity of the sensor with the SHS structure was 18.4 pm/℃ in the range of 30-130 ℃.The SGHGS-structured sensor has a temperature response sensitivity of 23.54 pm/ C in the range of 50-300 ℃.更多还原