基于纤锥反射装置的有源查询技术的研究

【作者】 曹雪；

【导师】 余有龙；

【作者基本信息】 黑龙江大学 ， 光学， 2007， 硕士

【摘要】 本文在研究光纤光栅(Fiber Bragg Grating，FBG)及光纤环形镜(Fiber Loop Mirror，FLM)工作原理的基础上，对FLM的性能进行了实验研究，建立了基于FBG和FLM反射技术的有源查询系统，成功的对10个FBG组成的传感网络进行了查询，并利用非平衡扫描Michelson干涉仪对传感信号进行了解调。论文全文从以下四个方面报道了硕士课题期间所完成的研究工作：(1)从布喇格方程出发，分析了FBG传感的基本理论以及应力、压力、环境温度对FBG的影响，最终给出了这三种物理量同时作用于FBG时，其布喇格波长总漂移量的数学表达式；通过分析宽带耦合器的耦合理论，介绍了以熔融拉锥法制作宽带耦合器的原理。利用预拉法使参与制作耦合器的两光纤间因结构不对称而具有不同的传播常数，从而研制出耦合比对波长响应平坦的宽带耦合器；以3dB耦合器制作FLM，讨论了FLM具有“全反射镜”特性的条件，提出可以利用双折射效应使FLM的反射率(透射率)发生改变。(2)基于研制的2×2型3dB宽带耦合器制作了FLM，对其光学性能进行了全面的实验研究，并对结果进行了必要分析。实验中观察到在耦合器宽带性能良好的波段范围内，FLM具有很好的“全反射”特性，反射率高于99.9％(忽略FLM的各种损耗)。(3)根据FBG的带阻滤波和FLM的“全反射”特性，提出并建立一种基于FBG和FLM的线性腔光纤激光器结构。利用内置偏振控制器(Polarization Controller，PC)，扭转光纤环，通过影响环中光纤内的应力分布，产生双折射效应，进而影响透射率(反射率)大小，成功地实现对激光输出功率在(0.485，6.86)mW范围内的调节。借助等腰三角形悬臂梁对FBG的工作波长进行调谐，实现了激光波长在(1555.065，1557.240)nm内的可调输出。(4)结合FBG及FLM的工作原理及特性，提出了一种新型的基于闭合腔的有源查询装置，将10个FBG传感元内置于FLM中，利用F-P滤波器对传感阵列进行波长扫描，实现各传感元的地址的查询；借助非平衡扫描Michelson干涉仪对传感信号进行了高分辨率解调，利用相位计探测包含待测信息的相移信息，从而达到测量待测应变的目的。该系统的传感灵敏度为1.5835 Deg／με，在误差允许范围内与理论值1.6662 Deg／με基本相符，分辨率为6 nε。更多还原

【Abstract】 The properties of fiber Bragg grating (FBG) and fiber loop mirror (FLM) have been studied experimentally based on the study of their principle. An active interrogating scheme, in which a cased wavelength division multiplexed (WDM) FBGs and an FLM have been employed to act as the end mirrors, has been proposed. An FBG array constructed by with 10 sensor elements was addressed, successfully, by introducing a tunable filter, which performs the function of wavelength scanning and an unbalanced Michelson interferometer demodulator. The research work will be illustrated from the following four aspects:(1) The effects of strain, press and temperature on FBG have been studied based on the Bragg equation. Then the theory of wide band fuse-tapered coupler was introduced. The wide band coupler was manufactured by the pre-pulling manner, which can result different propagation constants of the two fibers. Finally, the reflectivity of the FLM made by 3dB wide band coupler was investigated; it indicated that its reflectivity (transmissivity) can be changed by birefringence.(2)The characters of the FLM made by 2×2 3dB wide band coupler have been studied experimentally, and the results were discussed. It shows that the FLM has a reflectivity greater than 99.9% in the wavelength-flattened band of the coupler (the losses of FLM were neglected).(3)A configuration of linear cavity fiber laser based on FBG and FLM was presented according to the character of FBG and FLM. The distribution of stress in the fiber is changed by a Polarization Controller (PC), which is introduced to twist the fiber ring. The change of the distribution can result the birefringence effect; therefore, the reflectivity (transmissivity) of FLM is varied. The fiber laser has regulated output power in the (0.485, 6.86) mW and tuned laser wavelength in (1555.065, 1557.240) nm by tuning worked wavelength of FBG with triangle cantilever beam.(4)A novel active interrogating setup based on closing cavity was demonstrated according to the characters of FBG and FLM. It can interrogate 10 FBG sensor array placed in the FLM successfully by an F-P filter. The sensing signals of the FBG system were demodulated by unbalanced scanning Michelson interferometer; and phrase-shift signals, the measured strain signals included, were detected by phase meter. The sensor sensitivity of the system, 1.5835 Deg/με, is in good line with the theoretical value of 1.6662 Deg/με, and its resolution was 6ne.更多还原