长周期光纤光栅的传感解调研究

发布时间：2018-01-13 19:13

本文关键词：长周期光纤光栅的传感解调研究　出处：《广西师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：光纤光栅在光纤通信、光纤传感和光信息处理等领域的应用非常重要。根据折射率调制周期的长短可以分为长周期光纤光栅和布拉格光纤光栅,由于长周期光纤光栅是同向传输的纤芯基模和包层模之间的耦合,因此其谐振波长和损耗峰幅值对外界的温度、应力、折射率等因素的变化非常灵敏,与布拉格光栅相比,长周期光栅的灵敏度更高,测量精度会更高；同时长周期光纤光栅是一种透射型光纤光栅,没有后向反射,在传感测量系统中不需要使用隔离器。但长周期光纤光栅在传感方面的应用却远远不如布拉格光栅,最主要的原因就是没有合适的解调技术,而且长周期光纤光栅具有较大的损耗峰带宽,目前对于长周期光纤光栅的研究主要是在实验室,研究出低成本,高性能的解调仪器是长周期光栅传感研究的重点。文章对于长周期光纤光栅的发展研究有一个大体的概括,本文从麦克斯韦波动方程出发,通过耦合模理论对长周期光纤光栅进行分析研究,长周期光纤光栅是同向传输的模式之间进行耦合,分别推导纤芯基模和包层模式在传输过程中的色散方程,讨论不同模式之间的耦合,光纤光栅的谐振波长等问题,利用Matlab仿真出长周期光纤光栅的透射谱。长周期光纤光栅对外界环境敏感,温度,应力,折射率等因素的变化都会引起纤芯导模或包层模的有效折射率的改变,或者是引起光栅周期的变化,从而透射谱就会发生变化,谐振波长发生偏移,损耗峰幅值也会产生变化等等,通过分析透射光谱的变化情况可以得到外界温度、应力等参量的变化,从而能够实现解调的目的。针对长周期光纤光栅的传感特点,文章提出了一种基于可调谐F-P的解调方案,将传感光栅的透射光强转化为压电陶瓷施加电压的大小,通过电压大小的变化还原光强的变化,F-P解调的光谱范围比较广,精度比较高,是一种可行的长周期光纤光栅的解调方案。长周期光纤光纤有得天独厚的优势,制约其发展的主要因素是没有好的解调方法,找到合理的解调方法,长周期光纤光栅在传感领域必能会发挥更大的作用。
[Abstract]:The applications of fiber grating in optical fiber communication, fiber sensing and optical information processing are very important. According to the length of refractive index modulation period, it can be divided into long-period fiber grating and Bragg fiber grating. Because the long-period fiber grating is the coupling between the coaxial core and cladding mode, the resonant wavelength and the amplitude of the loss peak are sensitive to the temperature, stress, refractive index and other factors. Compared with the Bragg grating, the long period grating has higher sensitivity and higher measurement accuracy. At the same time, the long-period fiber grating is a kind of transmission fiber grating, which has no backward reflection. There is no need to use isolator in sensor measurement system, but the application of long period fiber grating in sensor is far less than that of Bragg grating, the main reason is that there is no suitable demodulation technology. And the long-period fiber grating has a large loss peak bandwidth. At present, the research of the long-period fiber grating is mainly in the laboratory, and find out the low cost. High performance demodulation instrument is the focus of long period grating sensor research. This paper has a general summary of the development of long period fiber grating, this paper starts from Maxwell wave equation. The long-period fiber gratings are analyzed by coupling mode theory. The long-period fiber gratings are coupled between the coaxial transmission modes, and the dispersion equations of the core based mode and the cladding mode are derived respectively. The coupling between different modes and the resonant wavelength of fiber grating are discussed. The transmission spectrum of long period fiber grating is simulated by Matlab. The long period fiber grating is sensitive to external environment, temperature and stress. The change of refractive index and other factors will cause the change of effective refractive index of the core guiding mode or cladding mode, or the change of grating period, so the transmission spectrum will change and the resonant wavelength will shift. Loss peak amplitude will also change and so on. By analyzing the change of transmission spectrum, we can get the change of external temperature, stress and other parameters. According to the sensing characteristics of long period fiber grating, a demodulation scheme based on tunable F-P is proposed. The transmission intensity of the sensing grating is converted into the applied voltage of piezoelectric ceramics, and the spectrum range of F-P demodulation is wider and the precision is higher. LPFF is a feasible long period fiber grating demodulation scheme. LPFF has unique advantages, the main factor restricting its development is that there is no good demodulation method to find a reasonable demodulation method. Long-period fiber grating will play a more important role in sensing field.
【学位授予单位】：广西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253

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