单/双泵浦BOTDA系统弹性非线性效应影响及抑制研究

Brillouin optical time-domain analysis (BOTDA) system has found wide applications in the fields of security monitoring such as electric power transportation, petroleum and chemical industry, and large-scale building structure. Recently, as the sensing distance increases, elastic fiber nonlinearity has placed restrictions on longer range of the system. Based on single-pump and double-pump BOTDA systems, this project focuses on the topic of elastic nonlinear effects. Firstly, a theoretical model will be proposed, which is mainly about the influences of pulse rising edge, trailing edge and top flatness on Brillouin gain spectrum through self-phase modulation (SPM) and cross-phase modulation (XPM). The pulse will be optimized considering both the power variation steepness and the lasting time. Secondly, the effects of modulation instability (MI) and four-wave mixing (FWM) on Brillouin gain will be simulated in the presence of phase noise. The influences of MI and FWM on the signal-noise-ratio (SNR) and sensing distance of the system will also be researched experimentally. Thirdly, based on the research about using fiber Bragg grating (FBG) to suppress MI, the physical mechanism of Brillouin gain flat region versus pump power will be searched. Finally, FWM and MI will be suppressed from the phase-mismatch viewpoint, using the double-pump BOTDA system. This project will enhance our understanding of the elastic nonlinear effects in the BOTDA system, and is of great significance for the suppression of elastic nonlinear effects and increasing of the sensing distance.

布里渊光时域分析系统在电力输送、石油化工、大型土木结构的安全监测等领域具有广阔的应用前景。近年来随着系统传感距离的增加，光纤的弹性非线性问题成为制约进一步远程传感的瓶颈。本课题以单泵浦和双泵浦布里渊光时域分析系统为对象，围绕系统中弹性非线性效应这一主题，首次提出建立脉冲上升下降沿、顶部平坦度等脉冲细节通过自相位调制和交叉相位调制影响布里渊增益谱的理论模型，结合功率变化陡度和持续时间对脉冲进行优化；仿真相位噪声存在时调制不稳定性和四波混频对布里渊增益的影响，在此基础上实验研究二者对系统信噪比和传感距离的影响；基于窄带光纤光栅滤波抑制调制不稳定性的研究，探索布里渊增益出现平坦区的物理机制；最后结合双泵浦布里渊光时域分析系统结构，提出从相位失配角度对四波混频进行抑制。本课题的开展有助于深化人们对布里渊光时域分析系统弹性非线性问题的理解，对抑制系统中弹性非线性效应、增大系统传感距离具有重大意义。

布里渊光时域分析系统在电力输送、石油化工、大型土木结构的安全监测等领域具有广阔的应用前景。近年来随着系统传感距离的增加，光纤的弹性非线性问题成为制约进一步远程传感的瓶颈。本项目以单泵浦和双泵浦布里渊光时域分析系统为对象，围绕系统中弹性非线性效应这一主题，建立了脉冲上升下降沿、顶部平坦度等脉冲细节通过自相位调制和交叉相位调制影响布里渊增益谱的理论模型，结合功率变化陡度和持续时间对脉冲进行了优化；仿真了相位噪声存在时调制不稳定性和四波混频对布里渊增益的影响，在此基础上实验研究了二者对系统信噪比和传感距离的影响；基于实际系统开展了抑制调制不稳定性的研究，探索了布里渊增益出现平坦区的物理机制。在上述工作基础上，本项目还对光纤环形腔孤子、光纤环形腔激光器、干涉型光纤传感系统中的非线性效应等内容进行了深入研究。本项目的开展有助于深化人们对布里渊光时域分析系统弹性非线性问题的理解，对抑制系统中弹性非线性效应、增大系统传感距离具有重大意义，所得结果对于光纤环形腔和干涉型传感等研究也有促进作用。在本项目资助下，发表SCI论文8篇，EI检索的国际会议论文6篇（口头报告2次），申请和授权专利2项，很好的完成了研究内容，实现了研究目标。