| 题名 | 复杂结构光纤光栅的逆工程设计和实验研究 |
| 作者 | 黄锐 |
| 学位类别 | 博士 |
| 答辩日期 | 2004 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 方祖捷 |
| 关键词 | 光纤光栅 逆工程设计 光通信 |
| 其他题名 | Synthesis and Experimental Research of Complex Structure Fiber Bragg Gratings |
| 中文摘要 | 人们对各种信息的巨大需求促使光纤通信系统不断发展。通信系统的发展和新功能的实现很大程度上取决于新型关键器件的开发和研制。光纤光栅以其优良的滤波特性、低插入损耗、偏振无关性、易于与其它光纤器件集成等特点，在光纤通信、光纤传感、激光和光信息处理等领域中获得了广泛应用。实际应用对光纤光栅的性能提出了越来越高的要求。也提出了多种具有复杂结构、性能特殊的光纤光栅的研发需求。本文对复杂结构光纤光栅的特性进行了理论分析和实验研究，改进了光纤光栅的性能；着重研究了进行逆工程设计的方法；应用该方法研制了新型光纤光栅；对光纤光栅在脉冲控制和传感中的应用进行了研究。本文的主要内容包括以下几个方面：比较分析了光纤光栅的各种理论描述和计算方法的优缺点，包括光栅的祸合模理论，多层膜理论，有效介质理论和相应的计算分析方法包括基于藕合模理论的龙格一库塔法，传输矩阵法，和基于多层膜理论的Rouard计算方法及傅立叶变换分析法。研究了光纤光栅的变迹技术，给出了光栅的常用变迹函数和变迹光栅的制作方法。在光纤光栅的相位版侧向写入技术的基础上发展了一种两步扫描曝光写入技术，实现了光纤光栅的纯变迹，大大抑制了反射峰的旁瓣，提高了器件的隔离度。提出了一种调节光纤光栅参数的方法，这对提高光栅的成品率，光栅参数的精确控制具有重要意义。理论分析了超结构光纤光栅，给出了提高超结构光纤光栅性能的方法。据此制作了间距为100GHz的取样光纤光栅。研究了取样光纤光栅长周期损耗效应带来的插入损耗特性，给出了降低这种插入损耗的方法。利用遗传算法，采用传输矩阵法计算光栅的光谱，以光栅的每一小段的折射率调制作为决策变量，采用浮点数编码方式，实现了光纤光栅的逆工程运算。利用遗传算法搜寻出了适合矩形光栅的折射率调制分布。利用遗传算法设计出了产生三角形光谱分布的光纤光栅的藕合系数沿光纤的分布。实验中，采用光束扫描法制备了反射带宽为0.77nm三角形光谱的光纤光栅。利用这根三角光栅作为波长读出器，进行了应变解调试验，即使在光源功率波动10％下，整个应变测量系统的精度依然可以低于1.5με，而且整个应变测量系统具有与光源功率波动、光源功率分布、传感光栅弯曲带来的损耗等因素无关的特性。研究了一种带宽大范围可调的斜边三角形光谱光纤光栅。基于遗传算法的逆工程设计表明，这种光纤光栅要求折射率调制函数为斜边三角函数。提出一种光纤外径沿轴向变化的结构，在拉应力下获得可调谐的斜边三角形光纤光栅，模拟计算了光栅结构参量对光栅反射光谱的影响。实验中用紫外激光光束扫描幅照法制作了斜边三角形光纤光栅；用程序控制的腐蚀方法制备光纤外径沿轴向的分布变化。在对光纤光栅施加不同的拉力，得到了不同带宽的斜边光纤光栅。斜边带宽调节范围为0.7nm到2.3nm。推导模拟了线性范围内超短脉冲在光纤光栅中的传输特性，对出射脉冲形状改变做了一个初步的理论说明。采用傅立叶变换法设计了使高斯脉冲变换到孤子脉冲的光纤光栅和使孤子脉冲变换到高斯脉冲的光纤光栅。数值模拟了所设计光栅的变换特性，模拟结果显示变换脉冲同目标脉冲波形符合的很好。最后设计出了一种用于ps级单脉冲变换到多脉冲的光纤光栅，并且变换输出光脉冲的谱形和脉宽与输入脉冲相同。这部分工作对于光栅在信号处理，多脉冲光源，超快光子学和光电子学、光学测量以及脉冲编码等领域中的应用具有指导作用。从分析光纤光栅的温度应变特性出发，分析了光纤光栅传感器的优点和特征，提出了两种用于同时测量温度和应变的光纤光栅。其一是利用宽取样光纤光栅的长周期损耗峰和布拉格反射峰的不同温度应变响应系数来同时测量温度和应变。其二是由两个周期相同但光纤直径不同的两个子光栅连接而成的复合光栅。理论分析和实验都证实了这两个子光栅具有相同的温度敏感性和不同的应变敏感性，由此实现光纤光栅传感器中温度和应变二参数的分离测量，而且这两个子光栅的中心波长间距可以直接测量应变大小，温度变化不影响所测量的应变值。 |
| 英文摘要 | The optical fiber transmission system has been growing rapidly driven by the great demands of the society for information. The development of communication system and the realization of new functions depend largely on the research of key devices. Fiber Bragg Gratings (FBGs) are widely used in the field of fiber communication, fiber sensing, laser technology and optical information processing due to their excellent characteristics, such as good filtering performance, low insertion loss, low polarization dependence and compatibility with fiber system. The practical applications require FBGs with better characteristics and with new and versatile functions. This dissertation puts emphasis on theoretical and experimental study of complex structure FBGs. The performance of FBG filters has been improved. The synthesis methods of FBGs have been developed; new FBGs have been synthesized and fabricated with the method; they are used in sensing. Applications of FBG in optical pulse reshaping have been also studied. The main research results in the dissertation include: Different theories and analysis methods of FBG have been compared, including coupled mode theory, multiple thin-film theory, effective medium theory, Runge-Kutta method and transfer matrix method based on coupled mode theory, Rouard's method based on multiple thin-film theory, and Fourier transform analysis method. Their advantages and disadvantages have been pointed out and discussed. Apodization technique of FBG has been studied, and apodization functions have been provided. A two-step scanning technique has been developed for pure apodization. The sidelope of the apodized FBG has been suppressed and the isolation has been improved. A trimming method for FBG parameters has been presented; the performance of FBG and the reproducibility of FBG fabrication have been greatly improved. Characteristics of superstructure fiber Bragg gratings (SFBGs) were analyzed and discussed. SFBG with channel spacing of lOOGHz was fabricated experimentally. Insertion loss characteristics of SFBGs were also investigated theoretically and experimentally and a method for reduction the insertion loss was presented. A genetic algorithm for the synthesis of FBGs has been proposed. The refractive-index modulation of each section of FBG is used as the decision variable. By floating-point cording, fiber gratings inversion computations are realized, along with the transfer matrix method for calculating the reflection spectrum of fiber gratings. A coupling coefficient distribution along the grating length was acquired for a rectangle and a triangular spectrum FBG by using genetic algorithms synthesizing. A triangular FBG with 0.77nm reflection bandwidth was fabricated experimentally by using a scanning method. This triangular FBG was proposed to be a wavelength readout device for fiber sensors. A strain sensing system with the proposed wavelength readout device was studied experimentally. It was shown that the result was immune from the light source power fluctuations, uneven spectrum of the light source, and attenuation of the sensing FBG caused by micro-bend and so on. A resolution of better than 1.5 jus was evaluated at the light source power fluctuations of 10%. The index modulation function of edge fiber Bragg grating (EFBG) was also acquired by using genetic algorithms synthesizing. A method for fabricating tunable EFBG by changing the diameter of the fiber along its axis and applying tension to the grating has been proposed and testified. The influence of physical parameters of the device on the edge filter's reflection spectrum was analyzed. An EFBG was fabricated by ultraviolet laser-scan and programmed etching in HF acid. The edge bandwidth of the FBG may be adjusted by tension, and the edge bandwidth was increased from 0.7nm to 2.3nm as the tension increased. Transmission characteristics of ultra-short pulses propagating through an FBG has been discussed and simulated in linear scope. A simple explanation for the shape changing of output pulse from FBG has been proposed. FBGs that could transform Gauss pulses to soliton or inversely, and a single picosecond optical pulse to muti-pulses were synthesized by using Fourier transformation method. The characteristics of the reflected pulses from the designed FBGs were examined by numerical calculation. The proposed FBG is believed to find applications in the area of ultra-fast optics, optoelectronics and optical measurement. The merits of FBG sensors have been analyzed based on the temperature and strain characteristics of FBGs. Two kinds of FBGs used for simultaneous strain and temperature measurement have been proposed and experimentally testified. One is based on the different temperature and stain response between LPG loss peaks and FBG peaks of high-duty-cycle sampled FBG to measure strain and temperature simultaneously. The other is a combined device composed of two FBGs with same period but different fiber diameter. Theoretic analysis and experiment data show that the two FBGs have the same temperature response but different strain response. Their strain and temperature responses can be measured simultaneously, and the spacing between peaks of the two FBGs can be used to measure the strain temperature-independently. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15338]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 黄锐. 复杂结构光纤光栅的逆工程设计和实验研究[D]. 中国科学院上海光学精密机械研究所. 2004. |
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