【作者】 孙琪真；

【导师】 刘德明；

【作者基本信息】 华中科技大学 ， 电子科学与技术， 2008， 博士

【摘要】 光纤传感技术是20世纪70年代伴随着光纤通信技术的发展而迅速发展起来的,以光波为载体,光纤为媒介,感知和传输外界被测量信号的新型传感技术。分布式光纤传感技术可以在整个光纤长度上对沿光纤分布的环境参量进行连续测量,同时获得被测量的空间分布状态,在民用和军事上具备广泛的应用前景,因此成为目前国内外研究的热点。本论文从长距离、高精度、多信道及信号解调简单等研究角度,针对全分布式、准分布式光纤传感和信息处理技术进行了深入的理论和实验研究,并探讨其应用价值。主要研究成果如下:(1)提出全分布式长程马赫-泽德干涉(MZI)及直流光环路定位两项创新技术,研究直线型和环型结构的两种新型MZI分布式光纤振动传感器,分别适合于长距离管线监测和周界监测,并实现了多点振动的高精度检测和准确定位。(2)提出一种环路反馈型非平衡MZI传感技术。通过无源或有源光纤反馈环路,在MZI中引入多光束干涉。相比传统MZI,其相位检测灵敏度提高2～3个数量级。(3)提出一种连续内刻高密度全同弱布拉格反射周期结构的新型传感光纤以及一种基于时间域和频率(波长)域二维空间数据分析的“光波长时域反射”的创新技术,可同步实现精密传感与准确定位,并由此构建大容量、长距离、精密测量、准确定位的准分布式光纤传感系统。(4)提出一种多信道的温度异常报警传感技术。利用多波长啁啾取样光栅的多信道波长反射特性,每个信道波长对应一个温度监测点,通过波长比对检测,结合时分复用技术实现超温报警与定位位置。这种传感器不需要波长解调,不同位置温度报警阈值可灵活设计,响应速率较高,非常适合于火灾探测报警。(5)提出一种基于线性啁啾光栅(LCFBG)的光波时延调制型光纤传感创新技术。利用LCFBG的线性群延时谱,通过测量单色脉冲光波经过光栅后引起的光时延变化确定待测参量大小。其优点是结构简单,在时域解调信号,从而省去波长解调器。这种传感器单元在准分布式传感中有很好的应用价值。更多还原

【Abstract】 Optical fiber sensing technology has been expanding rapidly along with the development of fiber communication technology from 1970’s, which employs the light wave as carrier and the fiber as medium to sense and transmit the measured external signals. The distributed sensing technology is able to continuously detect the environment parameters along the whole fiber, and obtains their spatial distribution. Therefore, the distributed sensing technology has broad application prospect in the civil and military fields, and becomes the investigation hotspot both in domestic and foreign countries.In this dissertation, the full-distributed and quasi-distributed fiber-optic sensing and information processing technologies are comprehensively investigated both in theories and experiments, according to the research points of view such as long distance, high precision, multi-channel, and easy signal demodulation. Also, their application value is discussed. The main research achievements are as follows:Firstly, the novel full-distributed vibration sensing technique which adopts the long distance Mach-Zehnder interferometer (MZI), and the novel direct current light and fiber loop based real-time and dynamic locating technique are proposed. Moreover, two full distributed vibration sensing systems, which are respectively based on the linear MZI and the ring MZI structure, are discussed and demonstrated. The two sensors can be used to achieve the long distance pipe-line and perimeter monitoring, respectively, by exploiting only one MZI. It should be noted that the ring MZI based sensor is capable of precisely detecting and exactly locating the multiple vibrations.Secondly, the new interferometric sensor with ring feedback non-balanced MZI is proposed and analyzed. By introducing the passive or active ring feedback, the multi-light-wave interference is generated in MZI. Compared with the conventional MZI, such sensor is able to boost the phase sensitivity by two to three orders.Thirdly, the novel distributed fiber in which high density identical periodic structures with low Bragg reflective are written, and the detecting technique named“Optical Wavelength Time Domain Reflection (OWTDR)”which utilizes the two dimension data analysis method of time domain and frequency (wavelength) domain are presented. Combined with the detecting technique, the special fiber is able to precisely sense and exactly locate the external signals simultaneously. As a result, the new quasi-distributed fiber sensing system of large capacity, long distance, precise measurement and exact locating is constructed.Fourthly, the multi-channel temperature abnormal warning sensing technique is presented. Based on the multi-channel wavelength reflection characteristic of the multi-wavelength chirped sampled fiber Bragg grating (FBG), each reflective channel wavelength corresponds to one different monitoring positions. The sensor examines whether the temperature exceeds the tolerable value by comparing the nominal wavelength of the sensing FBG to the corresponding channel wavelength, and locates the abnormal temperature with the time-division-multiplexed (TDM) technique. Due to the reasons of no need of wavelength demodulation, flexible setting of the tolerable temperature at different positions, and quick response, such sensor is very suitable for fire detecting.Finally, the novel optic time-delay modulation based sensing technique is presented. The key sensing principle is the linear group delay of the chirped FBG (LCFBG). When a pulsed monochromatic light is injected to the LCFBG, the resultant time-delay of the reflected pulse light varies with the value of the measured parameter. The sensor has several advantages, such as simple structure and no need of wavelength demodulation, to be well applied in the quasi-distributed sensing network.更多还原