【作者】 陈琳；

【导师】 陈向飞；

【作者基本信息】 南京大学 ， 材料物理与化学， 2013， 硕士

【摘要】 在信息时代,传感器具有越来越重要的地位,是现代社会的重要技术基础。光纤光栅传感作为无源传感器中的杰出代表,自出现以来,就以其优良的特性成为各个国家竞相发展的重要技术。本文首先介绍了光纤光栅传感的发展,并研究总结了光纤光栅各种解调方式。相比于无源传感系统,本人在研究过程中,发现有源传感具有无源传感所不具有的一些优势如：高信噪比,高输出功率以及易于检测等特点。所以本文中我们将无源传感升级为有源传感,提出了光纤激光传感,它不但保留了光纤光栅传感的技术特点,同时又克服了无源传感技术的不足。而在光纤激光传感器中,拍频解调技术是结构最为简单、又低成本同时还具备高精度的技术。因此本文侧重发展基于此种解调方式的光纤激光传感器。在第二章中对比光纤光栅传感的六种波长解调方案,发现每种解调方案都有瑕疵,所以在具体选择确定解调方案的时候,必须结合实际工程应用要求来仔细研究,斟酌。既然这些传感方案都或多或少地存在些许瑕疵,我们把目光投向光纤光栅有源传感技术。正是在无源传感技术的基础上,光纤光栅有源传感技术不断发展,它是用光纤激光器取代光纤光栅来作为传感头,从而形成有源传感系统。这样可以很明显地提高传感信号的信噪比,同时我们研究的拍频技术的解调方案使得较难检测的波长信号转换成拍频,在电域范围内检测,大大降低了信号解调的难度,是一种十分具有应用前景的传感技术。在第三章中,我们提出了基于拍频解调的光纤激光传感技术,首先介绍了多纵模光纤激光传感原理,然后详细介绍了多纵模模式和模式之间生成拍频信号的原理,并且通过实验证明了模式跳变现象对于此类传感器的检测结果几乎没有影响。在三个实验中,我们不但分析了物理量作用在谐振腔上所产生的效应和原理,实现了单个物理量信号的测量,而且我们还通过纵模拍频和偏振模拍频信号同时的检测,实现了两个物理量的同时传感检测。另外我们还研究讨论了多纵模光纤激光器所产生的多个拍频信号的选择问题,从需要达到的检测灵敏度,拍频信号信噪比以及实验过程中所能提供的条件等方面考虑,选出最佳的拍频传感信号。在光纤激光传感系统中,拍频解调方法相比其它传统的解调方法来说,是一种相当简单、全电子的光信号解调技术。简单且价格低廉的频率计就能够实现高精度的解调,极大程度上降低了传感器的成本,具有广泛地市场前景。更多还原

【Abstract】 In the Information Age, as an important technical foundation of modern society, the sensor plays a more and more important role. Fiber Bragg grating sensor is a outstanding representative of the passive sensor. This paper first introduces the development of fiber grating sensor and studies all kinds of fiber grating demodulation technique. And we found that the active sensing has some advantages that passive sensing does not have such as:high signal-to-noise ratio, high output power and ease of detection, etc. Considering of these shortcomings of passive sensing, in this paper we will make passive sensing upgrade to active sensing and propose optical fiber laser sensor, it not only retains the technical characteristics of the fiber grating sensor, but also overcomes the shortage of passive sensing technology at the same time.In the second chapter, we compare six kinds of wavelength of fiber grating sensor demodulation scheme and find that each demodulation has its flaws. Since there are more or less flaws existing in all the sensing schemes, we turn our gaze to the active fiber grating sensing technology. On the basis of passive sensing technology, the active sensing technology constantly developed, the Fiber Bragg grating in the passive sensing system is replaced by fiber laser and then active sensing system is formed. It can clearly improve the signal-to-noise ratio of the sensor, and the beat frequency demodulation technology convert the difficult-detecting wavelength signals into the beat frequency which can be detected in the electric field, which greatly reduces the difficulty of signal demodulation, so it is a very promising sensing technology.In the third chapter, fiber laser sensing technology based on beat frequency demodulation is proposed. Firstly we introduced the principle of multi-longitudinal-mode fiber laser sensing, and the principles of the beat signals generated between multi-longitudinal mode patterns and patterns, and we proved that mode hopping phenomenon almost has no effect on the detection result of such sensors through experiments. In the three experiments, through analyzing the principle of a physical quantity acting on the resonator, we can not only realize a single physical quantity signal measurement, but also achieve two physical quantities detection at the same time by detecting the longitudinal mode beat frequency and polarization-mode beat frequency signal. In addition, we also studied and discussed how to choose the best beat frequency signal from a large number of beat frequency signals generated in the multi-longitudinal-mode fiber laser sensor, the signal we choose should has high sensitivity and high signal-to-noise ratio at the same time. In the fiber laser sensor system, the beat frequency demodulation method is a very simple and full-electronic optical signal demodulation technique. The simple and inexpensive frequency-meter is able to achieve high-precision of demodulation, and it can reduce the cost of the sensor largely. In brief, the optical fiber laser sensor based on beat frequency demodulation has broad market prospects.更多还原