随着科学技术的发展，世界进入一个以传感器为基础、万物互联的信息时代。相较于传统电子传感器，光纤传感器体积小、重量轻、成本低、抗电磁干扰、远程测量、灵敏度高、耐用性好，已被广泛运用到土木建筑、航空航天、精密加工、生物医药等各行各业。干涉型光纤传感器是一种光纤点式传感器，具有广泛的应用前景。传统干涉型光纤传感器的灵敏度受石英材料的特性所限，在一些需要超高灵敏度的应用场景下并不适用。因此，寻求新的增敏机制来改善干涉型光纤传感器的性能具有实际研究价值。由于光对传播介质折射率变化十分敏感，可通过引入折射率变化显著的功能材料来提高干涉型光纤传感器性能。此外，根据干涉光谱类似标尺的等宽特性，光学游标效应被引入干涉型光纤传感系统，用于放大传感信号，实现传感器的增敏。本文研究了基于功能材料和游标效应增敏的干涉型光纤传感器，主要工作内容如下：（1）提出一种基于功能材料聚乙烯醇的光纤温度探针。在该温度探针中，聚乙烯醇用于填充二氧化硅微管，并与单模光纤集成。由于聚乙烯醇良好的热性能，该温度探针能在所测温度范围内同时通过干涉峰波长，干涉峰强度以及干涉条纹对比度来解调温度变化，降低检测的不确定度。此外，该温度探针体积小，通过收集反射式信号进行检测，在有限空间和远程探测中优势明显。（2）针对单个传感器传感灵敏度、探测范围固定的应用场景，提出一种基于游标效应的灵敏度、探测范围可调谐光纤温度探针。其通过串联可调谐非本征法珀干涉仪与基于保偏光纤的反射式利奥滤波器，在高灵敏度的基础上实现灵敏度、探测范围可调。该传感器可灵活适用于不同灵敏度和检测范围的应用场景。 （3）在传统的基于游标效应的光纤干涉温度传感系统中，游标光谱包络的高消光比与参考臂的温度不灵敏性往往不可兼得。为克服这个问题，我们提出一种基于混合熔接无芯光纤和空心光纤的在线式马赫-曾德尔干涉仪作为光纤干涉温度传感系统的参考臂。该干涉仪自由光谱范围可调，且干涉消光比几乎不变。此外，该干涉仪结构紧凑，降低传统基于游标效应温度传感系统的体积，增加其实用性。
With the fast development of science and technology, the world has entered a sensor-based information era with the interconnection of all things. Compared with traditional electronic sensors, fiber optic sensor is compact, lightweight, low-cost, anti-electromagnetic, remote operation, highly sensitive, durable, and has been widely employed in various industries including urban construction, aerospace, precision processing, and biomedicine. An interferometric fiber optic sensor is a kind of point-type sensor, which has a comprehensive application foreground. The sensitivity of traditional interferometric fiber optic sensors is limited by the intrinsic physicochemical properties of silica, thereby not suitable for some application scenarios requiring ultra-high sensitivity. Therefore, it is of practical significance to seek new sensitization mechanisms to improve the performance of interferometric fiber optic sensors.Light is sensitive to refractive index change of the propagation medium, therefore, functional materials with huge refractive index change can be introduced to be integrated with interferometric fiber optic sensors to improve the sensing performance. Besides, the Vernier effect is introduced into the interferometric fiber optic sensing system to amplify the signal shift, according to the unique spectral characteristics of interferometers, which is similar to the ruler. In this dissertation, interferometric fiber optic sensors based on functional materials and the photonic Vernier effect are systematically studied. The main works include:(1) A fiber optic temperature sensing probe based on polyvinyl alcohol (PVA) is proposed. In this device, the silica tube is filled with PVA and is integrated with single-mode fiber. Due to the good thermal performance of PVA, the temperature change can be demodulated by monitoring the wavelength shift, the intensity variation, and the fringe contrast evolution of the interferometric spectrum to reduce the uncertainty of detection in the temperature range. In addition, the temperature sensing probe is ultra-compact and can perform by analyzing the reflected signals, which is promising for the space-limited environment and with remote operation ability. (2) A fiber optic temperature sensor with controllable sensitivity and detection range based on the photonic Vernier effect is proposed. The sensitivity and detection range of the temperature sensor can be tuned on the basis of high sensitivity by cascading a tunable extrinsic Fabry-Perot interferometer (FPI) with a reflected polarization-maintaining-fiber-based Lyot filter. The sensor can be applied for application scenarios which need different sensitivities and detection ranges.(3) In the traditional Vernier effect-based fiber optic interferometric temperature sensing systems, the high extinction ratio of the Vernier spectral envelope and the temperature insensitivity of the reference arm are hardly compatible. To fix this problem, an on-line Mach-Zehnder interferometer (MZI) based on the hybrid fusion of no-core fiber (NCF) and hollow capillary fiber (HCF) is proposed as the reference arm of the Vernier effect-based fiber optic interferometric temperature sensing system. The free spectral range (FSR) of the interferometer is adjustable by modulating the length of the HCF and the extinction ratio is almost constant. In addition, the compact structure of the interferometer can greatly reduce the size of the Vernier effect-based sensing system and increase its practicality.
