基于差分放大的高精度分布式布里渊传感系统研究

发布时间：2018-05-11 18:49

本文选题：光纤传感 + 布里渊散射　；参考：《西南交通大学》2017年硕士论文

【摘要】：近年来,布里渊光时域分析(Brillouin Optical Time Domain Analysis, BOTDA)作为一项应用在长距离上的分布式光纤传感技术,可以用于任意位置上的温度和应变测量。因为其独特的优势,BOTDA技术被广泛地应用在大型工程设施的结构健康诊断上。为了进一步提高BOTDA在长距离测量过程中的信噪比,本文采用了基于差分放大的方法,来改进BOTDA传感系统。介绍了布里渊散射形成的物理过程,以及BOTDA技术的传感机制,研究了直接探测与相干探测的信噪比,分析了直接探测和相干探测BOTDA系统的噪声来源。并且,针对使用对数检波器的单边带调制相干探测BOTDA系统在样机集成的过程中,由于数据采集卡性能限制而产生的较大量化噪声的问题,采用了差分放大的方法,用来减小该量化噪声,提高传感系统的信噪比。该方法使用一个频率可调的微波信号和另外一个频率固定的微波信号来调制光源发出的激光,这两个微波信号的功率相同,被调制的光信号分别作为探测光和参考光。其中,探测光的频率在布里渊增益范围内扫描,而参考光的频率在布里渊增益范围之外。因此,只有探测光和本振光之间的拍频信号携带布里渊增益信息,而参考光和本振光之间的拍频信号不具有布里渊增益。然后,在经过降频之后,参考光和探测光的功率由两个对数检波器分别探测得到。将探测得到的两路信号送入差分放大器中,就可以消除多余的直流信号,并且布里渊信号被放大。同时,为了证实这种差分放大方法的有效性,又采用对比实验的方法对其进行了验证。此外,为了提升BOTDA系统在实际测量温度和应变时的运行效率,使该传感系统向着产业化方向发展,我们研究和探讨了 BOTDA系统实现自动控制所需的相关技术方法,并且在LabVIEW环境下编写了一套上位机软件系统以实现上述功能。该软件系统实现了对BOTDA系统各个模块的综合控制、对采集到的数据的存储和处理。此外,我们还添加了对测量结果和警报的显示功能。
[Abstract]:Brillouin Optical Time Domain Analysis, BOTDA) (Brillouin Optical Time Domain Analysis, BOTDA), as a distributed optical fiber sensing technique applied in long distance, can be used to measure temperature and strain at any position in recent years. Because of its unique advantage, BOTDA technology is widely used in structural health diagnosis of large engineering facilities. In order to improve the signal-to-noise ratio (SNR) of BOTDA in the long distance measurement, the differential amplification method is used to improve the BOTDA sensing system. The physical process of Brillouin scattering and the sensing mechanism of BOTDA are introduced. The signal-to-noise ratio of direct detection and coherent detection is studied. The noise sources of direct detection and coherent detection BOTDA systems are analyzed. In order to solve the problem of large quantization noise caused by the performance limitation of data acquisition card during the process of prototype integration, the differential amplification method is used to detect the single sideband modulation coherent BOTDA system using logarithmic detector. It is used to reduce the quantization noise and improve the signal-to-noise ratio of the sensor system. The method uses one frequency adjustable microwave signal and another fixed frequency microwave signal to modulate the laser emitted by the light source. The two microwave signals have the same power and the modulated optical signal is used as the probe light and the reference light respectively. The frequency of the probe light is scanned within the Brillouin gain range, while the reference light frequency is outside the Brillouin gain range. Therefore, only the beat signal between the probe light and the local oscillator light carries Brillouin gain information, while the beat signal between the reference light and the local oscillator light has no Brillouin gain. Then, the power of the reference light and the detection light are detected by two logarithmic detectors after the frequency reduction. When the detected two signals are fed into the differential amplifier, the redundant DC signal can be eliminated, and the Brillouin signal is amplified. At the same time, in order to verify the effectiveness of the differential amplification method, a comparative experiment is used to verify it. In addition, in order to improve the operating efficiency of BOTDA system when measuring temperature and strain, and to make the sensor system develop towards industrialization, we study and discuss the relevant technical methods needed to realize the automatic control of BOTDA system. And under the environment of LabVIEW, a host computer software system is written to realize the above functions. The software system realizes the integrated control of each module of the BOTDA system and the storage and processing of the collected data. In addition, we have added the display of measurements and alerts.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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