基于布里渊时域分析的长跨距单纤传感器关键技术研究

The optical fiber sensors based on Brillouin optical time-domain analysis (BOTDA) is always attracting research interests on temperature and strain measurement, because of the superiority in long distance sensor. However, its loop structure limits the geometric distance to half of its sensing ability and the noises of receiver limit the sensor performance. Moreover, in the conventional pulse coding technique, more than once pulse coding is launched into the sensing fiber to decode the information and pulse distortions will cause severe error. This project will focus on the study of these key technologies, which include the dual lasers is used in various positions instead of fiber loop configuration to avoid the depletion of the probe power in the leading fiber and achieve long sensing distance. And at the receiver part, an auto-balance low noise photo detector is proposed to reduce the influence of noise and lengthen the sensing distance, and novel pulse coding technique is also presented to achieve fast measurement with high SNR and enhance the tolerance to pulse power distortion. The study of these key technologies can develop the advantage of BOTDA technology and promote the development process of distributed sensor and attract more focus and discussion on the distributed sensor.

基于布里渊时域分析的光传感技术，由于其在长距离方面的突出优势，始终是分布式温度、应力传感领域的热门课题。但BOTDA系统实现长距离传感时环路结构的引入使得可检测的物理跨距减半，商用光接收机的底噪限制了系统性能、基于脉冲编码的应用需要多次打入脉冲进行解码且脉冲畸变会导致严重的解码错误等一系列技术难点仍待突破。为了解决BOTDA系统应用于长距离传感时存在的诸多技术瓶颈，本课题组提出使用2个异地锁频的激光器代替环路结构的方案，2个激光器处于不同地理位置，实现单纤长跨距传感；实现针对BOTDA系统大直流小信号特点的超低噪声自动平衡接收机，逼近噪声极限，降低了接收端噪声对系统的影响，进一步延长传感距离；提出新型编解码理论，实现快速动态测量，并降低因脉冲畸变导致的解码误差。这些关键技术的研究将使得基于布里渊时域分析的长距离分布式光纤传感器能够充分发挥其长距离传感的优势，推动分布式传感器研究的发展。

基于布里渊时域分析的光传感技术，由于其在长距离方面的突出优势，始终是分布式温度、应力传感领域的热门课题,但BOTDA系统实现长距离传感时环路结构的引入使得可检测的物理跨距减半，为了解决BOTDA系统应用于长距离传感时存在的诸多技术瓶颈，本项目展开了布里渊增益谱线宽压缩技术、热点附近布里渊频移提取技术、新型编解码技术、基于一阶拉曼放大的超长距离技术和单纤BOTDA系统研究，建立了编码BOTDA系统噪声模型。通过对这些技术的研究，实现了200公里、2m空间分辨率的长跨距的BOTDA系统，研究成果分别发表NATURE COMMUNICATIONS、OFS2022 PDP、JLT、OE等高水平杂志和会议上。通过本项目的研究，提出了编解码技术在BOTDA系统应用的极限增益模型、各种噪声对系统性能影响的理论模型、重新建立了在线拉曼放大技术应用于BOTDA系统时的能量转移模型，并通过超长距离实验验证。这些模型的建立，为实现BOTDA系统的极限性能提供了理论依据。

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