A novel fiber-optic magnetic field sensor with high interrogation speed and resolution by using an etched fiber Bragg grating (FBG) in conjunction with a dual-loop optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. A commercial FBG is firstly dipped into mixed hydrofluoric acid solution to remove the cladding layer and then is embedded with the magnetic fluid (MF) as a sensing element. The central wavelength reflected from the FBG is related to the overall time delay of the dual-loop OEO, which determines the oscillating frequency of the OEO. Therefore, the magnetic field can be estimated by measuring the oscillating frequency shift of OEO. The experimental results show that the oscillating frequency linearly increases with the increment of the magnetic field, achieving the sensitivity of 16.3 Hz/Oe with an R-square of 0.991 in the range of 5 mT-10 mT. In addition, the maximum error is within ±0.05 mT in the range of 7 mT-8 mT, which offers potentials in many fields where the high-precision magnetic field measurement is required.

提出并制备了一种基于本征倏逝波原理的温度及葡萄糖溶液浓度传感器.通过研究腐蚀包层厚度与透射光谱之间的关系, 确定较为合适的腐蚀厚度.将标准单模光纤包层腐蚀至2.4 μm, 利用光纤倏逝波对外界介质变化敏感的原理, 通过测量输出光功率的变化量实现温度及葡萄糖溶液浓度传感.实验结果表明：传感器在10~70 ℃的温度范围内具有9.58×10－3 dBm/℃的灵敏度, 线性度达到99.36%; 在葡萄糖溶液0~3%的浓度范围内具有0.126 dBm/(g/L)的灵敏度, 线性度达到97.95%.该传感器的响应时间小于30 s, 具有操作简便、测量准确度高、重复性好、适用范围广等优点, 具备良好的应用价值.

提出一种基于光纤腔衰荡系统并以一小段包层腐蚀光纤作为传感头的液体挥发测量方法, 同时搭建相应的实验装置进行了实验研究.从模式理论出发分析单模光纤传输模场的能量分布, 并采用有限元法数值模拟光纤端面能量的分布, 结果表明: 包层越细的单模光纤对应越大的消光系数, 即泄露出来的倏逝波能量越大, 从而对外界环境更敏感, 但是较细包层的单模光纤存在的损耗更大.综合分析得出腐蚀光纤的最佳直径应为26 μm, 最佳腐蚀长度为1 cm.通过实时监测衰荡谱的衰荡时间变化, 得到了30 ℃恒温环境下, 乙醇与丙三醇混合溶液中乙醇浓度随挥发时间的变化曲线.实验结果表明, 混合溶液中乙醇的浓度随挥发时间呈单指数规律衰减, 该变化规律与理论分析相符.由于液体浓度与其折射率成正比, 随着乙醇的挥发, 混合溶液的折射率逐渐接近光纤包层的折射率, 使其对腐蚀光纤纤芯中泄漏的倏逝波能量的吸收程度逐渐增大, 环腔的衰荡时间也相应逐渐减小.此外, 该监测方法在常温下具有较低的温度交叉敏感性.

Using a center etched single mode optical fiber, a simple vibration senor is designed to monitor the vibrations of a simply supported beam. The sensor has high linear response to the axial displacement of about 0.8 mm with a sensitivity of 32 mV/10 μm strain. The sensor is tested for periodic and suddenly released forces, and the results are found to coincide with the theoretical values. This simple design, small in size and low cost sensor may find applications in industry and civil engineering to monitor the vibrations of the beam structures and bridges.