【作者】 刘华伟；

【导师】 孙小菡；

【作者基本信息】 东南大学 ， 物理电子学， 2020， 硕士

【摘要】 以相位敏感光时域反射计(φ-OTDR)和偏振敏感光时域反射计(P-OTDR)为代表的分布式光纤振动传感(DOFVS)技术已在大型设施健康监测、重点设施周界安防、管道防护、海洋工程等领域展现出重要的应用价值和前景。然而,DOFVS系统在工程应用时出现了定位漂移较大、多点振动检测难度较大、恶劣环境下误报率较高、数据处理算法实时性较差等问题。偏振相关性是导致DOFVS系统恶化性能的主要因素之一。本文针对系统偏振相关性带来的工程应用问题,提出了三种解决方案,建立了仿真和实验系统,验证了方案的可行性。首先,定义了传感光子“组合态”和“能级裂变”的概念,给出了考虑偏振态的传感光子态函数表达式,建立了DOFVS系统的量子传感模型,给出了DOFVS系统传感原理的量子解释。建立了考虑偏振态的DOFVS系统光传输矩阵模型,推导得出考虑偏振态时微分干涉型DOFVS系统输出信号表达式,仿真分析了系统功率传输系数与延时光纤、传感光纤、入射光的偏振角之间的关系,提出了抑制DOFVS系统中偏振衰落现象的措施。接着,提出了一种基于联合卡尔曼滤波和信息融合的振动定位逼近算法。分析了偏振相关振动感知脉冲的随机漂移原因,建立起其随机漂移模型。实验研究了基于幅度-矩、空间漂移特征的预定位结果,以及将两者滤波、融合后的定位逼近结果。结果表明:在传感距离为10km、采样30次条件下,平均定位离散度<0.65m、最大定位离散度<2.2m、响应时间<80ms;与滑动平均、小波去噪法相比,该算法平均、最大定位离散度分别降低了75%、83%。然后,提出了一种基于P-OTDR谐波累加的DOFVS系统多点振动定位算法。推导出了振动感知信号频率与各振动频率之间的关系,证明了利用谐波累加实现多点振动定位的可行性。建立了系统仿真模型,仿真研究和实验验证了算法性能。结果表明:该算法可以解决多振动事件的叠加串扰问题,实现多点振动检测,同时避免了传统谱分析方法在定位多点不同频振动时的漏报问题。最后,提出了一种自适应偏振衰落抑制DOFVS系统和两种长距离DOFVS系统。分析了系统功率代价,证明了两种长距离DOFVS系统可将传感距离提升10km。推导出了无、有振动时系统中背向散射信号表达式,仿真分析了有振动时的背向散射迹线、基于功率极差、标准差的定位结果、系统频率响应特性,以及定位特征值与延时光纤的关系,结果表明基于φ-OTDR的长距离DOFVS系统定位性能更加优异。更多还原

【Abstract】 Distributed optical fiber vibration sensing(DOFVS)technology represented by phasesensitive optical time domain reflectometer(φ-OTDR)and polarization-sensitive optical time domain reflectometer(P-OTDR)has been used in large facility health monitoring and key facility perimeters Security,pipeline protection,marine engineering and other fields show important application value and prospects.However,the DOFVS system has problems in engineering application,such as large positioning drift,difficult multi-point vibration monitoring,high false alarm rate in harsh environments,and poor real-time data processing algorithms.Polarization correlation is one of the main factors that cause the deterioration of the performance of the DOFVS system.In this paper,three solutions are proposed for the engineering application problems caused by the polarization dependence of the system.The feasibility of the solution is verified by establishing simulation and experimental systems.Firstly,the concepts of sensing photon ‘sensing state’ and ‘energy level fission’ are defined,the expression of sensing photon state function considering polarization state correlation is given,the quantum sensing model of DOFVS system is established,and the quantum interpretation of sensing principle of the DOFVS system is given.The optical transmission matrix model of DOFVS system considering polarization state is established,and the output signal expression of differential interference DOFVS system considering polarization state is derived.The relationship between the power transmission coefficient of the system and the delay optical fiber,the sensing optical fiber,the interference phase difference of the light wave and the polarization angle of the incident light is analyzed by simulation,and the measures to suppress the polarization fading phenomenon in the DOFVS system are proposed.Next,a vibration location approximation algorithm based on joint Kalman filtering and information fusion is proposed.The causes of random drift of polarization-dependent vibration sensing pulses are analyzed,and the random drift model is established.The experiment studies the pre-positioning results based on the spatial drift feature and the amplitude-moment feature,and the positioning approximation result after filtering and fusing the two features.The results show that the proposed algorithm can achieve an average positioning dispersion of less than0.65 m and a maximum positioning dispersion of less than 2.2m within a response time of 80 ms.Compared with the moving average and wavelet denoising methods,the average and maximum positioning dispersion are reduced 75% and 83%.Then,a P-OTDR multi-point vibration positioning algorithm based on harmonic accumulation is proposed.The relationship between the frequency of the vibration sensing signal and each vibration frequency is derived,which proves the feasibility of using harmonic accumulation to achieve multi-point vibration positioning.The simulation model of the system is established,and the performance of the algorithm is verified by simulation and experiment.The results show that the algorithm can solve the problem of superimposed crosstalk of multivibration events,realize multi-point vibration detection,and avoid the problem of underreporting of traditional spectral analysis methods in multi-point vibration detection with different frequency.Finally,an adaptive polarization fading suppression DOFVS system and two long-distance DOFVS systems are proposed.The power cost of the system is analyzed,and it is proved that the two long-distance DOFVS systems can increase the sensing distance by 10 km.The expression of the backscatter signal in the system with and without vibration is derived,and the backscatter trace with vibration,the positioning results based on power range and standard deviation,the frequency response characteristics of the system,and the relationship between the positioning eigenvalues and the delay optical fiber are simulated and analyzed.The results show that the positioning performance of the long-distance DOFVS system based on φ-OTDR is more excellent.更多还原