基于混沌布里渊动态光栅的分布式温度和应变无交叉敏感测量研究

The Brillouin-based distributed fiber sensing technology has important applications in many fields such as construction, electric power, chemical engineering and aerospace. However, the cross sensitivity of the temperature and strain in the practical measurement is an important scientific issue to be imminently resolved. The conventional solutions face the technological difficulty of the low temperature and strain measurement accuracy. The Brillouin dynamic grating (BDG) method can increase the measurement accuracy of the temperature and strain. However, the BDG method presents serious drawbacks. For example, the pulse-generated BDG is refreshed periodically, so its amplitude actually oscillated with time, and its effective grating length is limited by the phonon lifetime. For the sine-modulation-based BDG, the periodicity of the frequency-modulated CW signal leads to the creation of multiple BDGs. This severely limits the spatial resolution and sensing distance of the distributed sensing system..This project proposes a chaotic BDG-based distributed fiber sensing method. The output from chaotic laser source is served as two pump waves, and they are injected into a polarization-maintaining fiber (PMF) from both ends, respectively. The stimulated Brillouin scattering occurs at the meeting position. When one beam of chaotic pump light provides the gain to the other, the chaotic BDG simultaneously emerges due to the interference of two chaotic pump waves. On the one hand, the temperature and strain coefficients of Birefringence-induced frequency shift (BireFS) are obtained by reading the reflection spectrum of the probe pulse via the chaotic BDG reflection. On the other hand, the temperature and strain coefficients of Brillouin frequency shift (BFS) are achieved by measuring the Brillouin gain spectrum. Thus, the simultaneous temperature and strain measurement is realized without cross sensitivity of the temperature and strain. The chaotic BDGs have special advantages such as the creation of single, permanent and localized BDG and the grating length of an order of centimeter. This ensures that the chaotic BDG-based distributed fiber sensing technology has the technological advantages of the high spatial resolution and long sensing distance.

布里渊分布式光纤传感技术在土木、电力、化工、航天等领域具有重要应用，但在测量中存在温度和应变的交叉敏感，是该领域急需解决的重要科学问题。常规的解决办法面临温度和应变测量精度低的困难。布里渊动态光栅（BDG）法可以提高其测量精度，但因光栅长度受限于声子寿命、光栅不稳定、容易产生多光栅等问题，严重制约空间分辨率和传感距离。.本项目提出一种基于混沌BDG的分布式光纤传感方法。利用混沌激光作为两路泵浦光，分别从保偏光纤的两端入射其中，在相遇处发生受激布里渊散射，在一路混沌泵浦光为另一路提供增益的同时产生了混沌BDG。一方面，通过探测脉冲读取混沌BDG的反射谱，获得双折射频移的温度和应变系数；另一方面，通过测量布里渊增益谱，获得布里渊频移的温度和应变系数，从而实现温度和应变的无交叉敏感测量。混沌BDG因具有单光栅、长时间稳定维持、光栅长度为厘米量级的特性，确保了高空间分辨率、长传感距离的技术优势。

布里渊分布式光纤传感技术在土木、电力、化工、航天等领域具有重要应用，但在实际测量中存在温度和应变的交叉敏感，是该领域急需解决的重要科学问题。本项目采用基于混沌布里渊动态光栅（BDG）技术实现了温度和应变的无交叉敏感测量。主要开展的研究及取得的成果如下：提出了多个宽带混沌激光产生方案，实验获得了频谱带宽达50GHz的混沌激光。利用宽带混沌激光实验产生了单一的、长时间稳定维持且光栅长度可控、厘米量级的BDG，基于混沌BDG技术获得了温度精度为0.3℃、应变精度为11με的温度和应变同时测量。基于混沌BDG的布里渊光相关域分析（BOCDA）传感技术，实现了空间分辨率为3.1mm的温度与应变分布式测量，通过斜坡辅助技术又实现了动态范围为1200με、测量精度为3.9με的应变分布式测量。进一步拓展高性能拉曼分布式光纤传感仪样机的研制及在输电线路运行状况监测的应用研究。在项目支持下，发表期刊学术论文43篇，SCI收录31篇次，授权国家发明专利12项。获2019年山西省自然科学二等奖、2020年山西省专利二等奖、2021年中国专利优秀奖、2021年山西省技术发明二等奖等4项。培养博士研究生2名、硕士研究生10名，其中1名评为山西省优秀硕士学位论文。