【作者】 杨光；

【导师】 裴丽；

【作者基本信息】 北京交通大学 ， 电磁场与微波技术， 2011， 硕士

【摘要】 近年来,准分布式光纤光栅传感技术凭借着测量精度高、测量距离远、可多点分布式测量、寿命长、适应各种恶劣环境等优势,在现代工程长期实时健康监测领域中的应用越来越广泛,而作为整个传感系统核心器件的法布里玻罗腔滤波器(FP腔滤波器)更是目前的研究热点之一。本文利用重叠写入啁啾光栅技术,分别应用不同方法形成FP腔滤波器,应用耦合模理论对其进行理论分析,并结合实验及仿真结果对各种方法进行比较。本文的主要工作及创新点如下：1.概述光纤及光纤传感技术的发展历程及其在实际中的应用现状,分析比较了目前几种主要FP腔滤波器的结构和特点。2.详细阐述FP腔滤波器的原理,分析了FP腔滤波器的装置结构,调谐过程以及自由光谱范围。介绍光纤光栅的理论模型,并应用耦合模理论,分析啁啾光栅的光谱特性和折射率调制。基于对FP腔滤波器和啁啾光栅的研究,利用重叠写入啁啾光栅形成FP腔滤波器。3.比较了三种形成FP腔滤波器的方法,即啁啾光栅串联法,施加应力重叠写入啁啾光栅法和移动相位掩模板重叠写入啁啾光栅法。啁啾光栅串联法结构简单,但由于啁啾光栅长度过长,梳状透射光谱不明显。应用施加应力法重叠写入啁啾光栅法,可形成明显梳状透射光谱,证明了利用重叠写入啁啾光栅形成FP腔滤波器的可行性。移动相位掩模板法可形成明显的梳状透射光谱,并且可精确控制两段啁啾光栅中心波长的偏差,透射光谱的自由光谱范围明显展宽。4.理论分析了移动相位掩模板重叠写入啁啾光栅法制作FP腔滤波器的特性,获得高精细度谐振峰的参数特性,并分析了啁啾光栅的啁啾量大小对FP腔滤波器性能的影响。结果表明,两段啁啾量为3nm的啁啾光栅重叠写入同一段光纤后,透射光谱可形成精细度良好的谐振峰,自由光谱范围可达1.3nm；重叠写入啁啾量4nm的啁啾光栅后,自由光谱范围可达1.7nm,重叠写入啁啾量5nm的啁啾光栅后,谐振峰仍保持较高的精细度,自由光谱范围可达2nm,完全满足单路传感光栅波长解调的要求。5.分别采用施加应力法和移动相位掩模板法进行实验,在同一段光纤中,重叠写入啁啾光栅形成FP腔滤波器。两种方法,都可形成明显梳状透射光谱,且使用移动相位掩模板法,透射光谱的自由光谱范围可达0.6nm。实验结果表明,利用廉价而又成熟的啁啾光栅重叠写入技术可以形成FP腔滤波器。更多还原

【Abstract】 In recent years, taking the advantages of the high accuracy, the long distance of measuring, multiple-point measurement, the long lifetime, adapted to all kinds of severe environment and so on, the applications of quasi-distributional optical fiber grating sensing technique, are getting more and more widespread in the long-time and real-time health monitoring of modern projects, then as the key device of the whole sensing system, Fabri-Perot cavity filter(FP cavity filter)is one of hot spots of research at present.This article makes use of the technique of superimposing chirped Bragg gratings to form FP cavity filter with different methods, analysis its theory with the coupled mode theory, makes comparison to each method combining with the results of experiments and simulations. The major and innovation work is as follows:1. Summarized the development process and the current application situation of optical fiber as well as the optical fiber sensing technique, introduced several main kinds of FP cavity filter’s structures and the characteristics.2. Elaborates the FP cavity filter’s principle in detail, analyzed the mechanism structure of FP cavity filter, harmonious process as well as free spectral range; Introduced the theoretical model of fiber Bragg gratings, and using pair matched molds theory, analysis the spectral characteristic and the modulation of refractive index of superimposed chirped Bragg gratings. Proposed the FP cavity filter formed by superimposed chirped Bragg gratings based on the research of FP cavity filter and the chirped Bragg gratings.3. Compared three methods of forming FP cavity filters, method of chirped Bragg gratings series, superimposing chirped Bragg gratings with method of forcing stress, superimposing chirped Bragg gratings with method of phase mask shifting.The structure is simple in using method of series chirped Bragg gratings, but there is no obvious comb-like transmission spectrum because the chirped Bragg gratings are too long. There is obvious comb-like transmission spectrum after superimposing chirped Bragg gratings with method of forcing stress. This method had proven the feasibility of forming the FP cavity filter with superimposing chirped Bragg gratings.. With the method of method of phase mask shifting to superimpose chirped Bragg gratings, there is also comb-like transmission spectrum, and the gap between two chirped Bragg gratings’ central wavelength can be controlled accurately, in addition, the free spectral range in transmission spectrum is wider obviously.4. Analyzed the characteristics of FP cavity filters by superimposing chirped Bragg gratings with method of phase mask shifting in theory, then obtained the parameters of resonance peak with nice fineness, and analyzed the influence of chirp quantity to the performance of FP cavity filters. The simulation result indicated that after superimposing chirped Bragg gratings with chirp quantity of 3nm, there is resonance peak with nice fineness, and the free spectral range could reach 1.3nm; after superimposing chirped Bragg gratings with chirp quantity of 4nm, the free spectral range could reach 1.7nm; after superimposing chirped Bragg gratings with chirp quantity of 5nm, the fineness of resonance peak also remained nice,the free spectral range could reach 2nm.It is enough for single channel demodulation of wavelength.5. Made experiments with methods of stress forcing and phase mask shifting separately, superimposed chirped Bragg gratings in the same fiber to form FP cavity filter. There are both comb-like transmission spectrums with both two methods. And the free spectral range could reach 0.6nm with the method of phase mask shifting. It indicate that it can formed FP cavity filter with the mature and cheap technique of chirped Bragg gratings superimposing by the result of the experiments.更多还原