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题名	相移光纤光栅的光热效应研究
作者	丁孟
文献子类	硕士
导师	陈迪俊
关键词	相移光纤光栅 Phase-shifted Fiber Bragg gratings 光热效应 Photothermal Effects 激光器 Laser 损耗 Loss 滤波器 Wavelength Filtering Devices
其他题名	Research on The Photothermal Effect of Phase-shifted Fibre Bragg Gratings
英文摘要	相移光纤光栅是一种特殊设计的光纤光栅。它通过在普通光纤光栅某一位置引入相移的方式，在光纤光栅的反射带内打开了一个窄带透射峰。作为一种窄线宽在线光纤滤波器，在激光器、微波光子学、光纤传感等方面得到了广泛的应用。由于人们对光纤窄带滤波器的渴求，相移光纤光栅的刻写工艺逐步完善，透射峰线宽越来越窄，其光热效应越来越突出，成为制约其应用的一个因素。但是，在近透射峰波长的激光入射下，相移光纤光栅的光热效应并未得到仔细的研究。本论文系统地分析了影响相移光纤光栅透射峰的各种因素，对其光热效应从理论到实验上进行了全面的研究，同时将相移光纤光栅插入到基于SOA的光纤环形激光器中作为窄带滤波器，测量了输出激光的特性，并对输出激光的不稳定行为进行了解释。主要内容如下： 1、理论上基于耦合模方程建立了?相移光纤光栅光热效应的理论模型，针对透射峰漂移比较大时，不能再用?相移光纤光栅近似的情况，用等效F-P腔法进行了分析。由于相移光纤光栅是一种特殊的光纤光栅，本文首先从模式耦合理论出发，推导了弱波导近似下的光纤光栅的耦合模方程，在均匀调制条件下，求解了光纤光栅的耦合模方程，分析了紫外辐照导致的折射率本底增加值、均匀背景损耗和周期性背景损耗对光纤光栅的影响。用传输矩阵法仿真相移光纤光栅的传输谱时，由于所需取样点比较密集，数据量通常比较大，仿真耗时比较长。本文改进了传输矩阵法，提出了矩阵复乘法，使得用MATLAB仿真时效率提高了10倍以上。针对单峰相移光纤光栅，提出了等效F-P腔法，利用该方法分析了相移点位置、相移量和损耗对相移光纤光栅传输谱的影响，给出了一部分情况下的解析公式，给相移光纤光栅的应用提供了参考。 2、实验上设计了基于PBS偏振分束的“泵浦-探测”系统，测量了不同波长和功率的激光入射时光热效应的透射峰波长漂移现象和相移光纤光栅的透射谱以及不同环境下波长漂移量与入射激光功率的关系。利用动态扫描法分析了相移光纤光栅光热效应的动态响应。从理论上探讨了通过增加相移段长度这一手段减弱光热效应的可能性，得出了这种方法改善光热效应效果有限的结论。 3、将相移光纤光栅插入到基于SOA的光纤环形激光器中作为窄带滤波器，测量了输出激光功率、波长和光谱随泵浦电流变化的情况，发现一种奇特的不稳定现象，利用PSFBG的光热效应对这一现象作出了初步解释。; Phase-shifted fibre bragg grating (PSFBG) is one kind of specially designed FBGs. By introducing a phase-shifted region in a general FBG, it opens a ultra-narrow transmission peak in the reflection band of FBG. As a ultra-narrow in-line fibre filter, phase-shifted FBG finds a broad range of application in the field of lasers, microwave photonics, fibre sensing and optical calculator. Due to the desire of ultra-narrow fibre filter, phase-shifted FBG’ fabrication technologies are gradually improved so that the transmission peak linewidth is narrower leading to its more and more prominent photothermal effect which has become a factor restricting its application. However, the photothermal effect of phase-shifted FBG has not been studied carefully. In this thesis, the factors influencing the transmission peak of phase-shifted FBG are systematically analyzed, and the photothermal effect is studied from theory to experiment. At the same time, a phase-shifted FBG is inserted into the ring fiber laser cavity as a narrowband filter and its effect on the output performance of the laser is analyzed. The main contents of this paper are as follows: 1.A theoretical modal of pi-PSFBG’s photothermal effects is built. For the case that PSFBG cannot be approximated as pi-PSFBG because large peak shift, an equivalent FP cavity method is proposed. Since PSFBG is one kind of specially designed FBGs, firstly, the thesis deduced the coupled mode equations of FBG under weak waveguide approximation from the mode coupling theory. Under the condition of uniform modulation, the coupling mode equation of the FBG is solved, and the influence of the background value of the refractive index, the uniform background loss and the periodic background loss on the fiber grating is analyzed. The transfer matrix method is improved, making its operation speed in the MATLAB increased by 10 times. For single-peak phase-shifted FBG, an equivalent FP cavity method is proposed. The influence of the phase shift point position, phase shift amount and background loss on the phase-shifted FBG transmission spectrum is analyzed by this method. The analytical formulas under some case are given, which provides a reference for the application of phase-shifted FBGs. Then a theoretical modal of ?pi-phase-shifted FBG is built to analyse optical field distribution of phase-shifted FBG at different laser wavelength. The thermo-steady-state equation in the case of photothermal effect is deduced to solve the temperature field distribution of phase-shifted FBG. The drift of the transmission peak wavelength is simulated and the bistability that the transmission peak wavelength drift is different in the forward and backward scanning of the incident laser is analysed. 2.In the experiment, PBS-based polarization splitter “pump-detection” system is designed to measure the peak shift and the transmission spectra of the phase-shifted FBG at different wavelengths and powers, and the relationship between the wavelength shift and the incident laser power in different environments. The dynamic response of phase-shifted fiber gratings is analyzed by dynamic scanning method. When the transmission wavelength shift is relatively large, it no longer increase with the incident optical power in a linear relationship. The thesis gives a theoretical explanation to the phenomenon. The possibility of weakening the photothermal effect by increasing the length of the phase-shifted region is discussed theoretically, and the conclusion is drawn that the method has its limit of weakening the photothermal effect. 3.The phase-shifted fiber grating is inserted into a SOA-based fiber ring laser (SFRL) as a narrowband filter. The laser’s output power, wavelength and spectrum with the pump current were measured, and we found a strange instability phenomenon. A preliminary explanation of this phenomenon is made based on the photothermal effect of PSFBG.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31013]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	丁孟. 相移光纤光栅的光热效应研究[D].

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