基于调频脉冲和稀疏采样的分布式声场传感技术研究

Acoustic field detection plays an important role in the fields of large structural defect detection, aircraft vibration modal analysis, and fault diagnosis of ship and automobile. Optical fiber distributed acoustic field sensing offers a number of advantages over conventional sensors, including the anti-electromagnetic interference, high-temperature tolerance, and multi-point measurement, which is very suitable for online acoustic field sensing in complex industrial environments. However, due to the low measurement accuracy, and the restriction in the frequency response range and sensing capacity, the application of fiber distributed acoustic field sending is limited. To enhance the sensing performance, this project proposes a sensing method based on frequency modulation laser pulse and sparse sampling. In order to improve the sensing accuracy, the transmission and restriction mechanism of signal to noise ratio of frequency modulation pulse based system is studied in the context of optical nonlinear effects and laser frequency drift. Then the sparse sampling model and waveform reconstruction algorithm are established based on compressed sensing theory, and the frequency response range would be widened without broadening the system modulation bandwidth. The high spatial resolution is ensured by the large modulation and detection bandwidth in experiment. Finally, the 2D acoustic field will be reconstructed, and the structural health state can be characterized by the properties of the detected acoustic fields. The obtained results can not only help to realize a high-precision, wide-frequency and large-capacity fiber-optic distributed acoustic field sensing system simultaneously, but also provide a new measurement method for structural defect detection and equipment fault diagnosis.

声场探测在大型结构的缺陷检测、航空航天器的振动模态分析、船舶和汽车的故障诊断等工程领域具有重要作用。光纤分布式声场传感具有抗电磁干扰、耐高温恶劣环境、多点同时测量等优势，非常适合于复杂环境中大型结构的在线声场传感，但目前由于测量精度不足、频响范围和传感容量之间彼此制约等问题，限制了其在声场健康监测领域的深入应用。本项目提出调频脉冲和稀疏采样结合的方法，研究调频脉冲在光学非线性效应和激光频率漂移等因素下的信噪比传递和制约机制，提高声场传感精度；研究基于压缩感知的低冗余稀疏采样模型和波形重构算法，在不影响系统脉冲调制带宽的前提下拓宽声场频响范围；提高脉冲调制和信号探测带宽确保系统的空间分辨率，并利用二维声场传播特性表征结构健康状况。研究成果有望同步实现高精度、宽频响和大容量的光纤分布式声场传感，为基于声场传感的结构缺陷检测和设备故障诊断提供新的测量手段。

近年来，在“一带一路”和新型城镇化新时代背景下，以油气、交通运输、电力、水利等方面为代表的基础设施建设成为我国经济快速增长的主要动力之一，而针对已建成和正在筹建的重大工程健康监测问题，成为新时代传感技术持续关注的焦点。长距离光纤分布式声/动态应变传感在油气管道等大型基础设施监测、矿产资源开发、地质灾害预防和城市地下空间监控等领域具有重要作用，但目前长距离光纤分布式声/动态应变传感存在探测精度不足、频响范围和空间分辨率无法同时提高等问题。为了突破长距离声/动态应变性能下降的瓶颈，本项目深入探索了频率调制光在分布式传感中的技术难题，研究了基于调频光的光纤分布式声传感和动态应变传感的关键性能参数，掌握了基于稀疏采样的分布式声信号采样原理和频率拓展规律，实现了非线性调频脉冲稀疏声信号采集系统、大动态应变准分布式声传感系统、光学啁啾链动态应变系统的参数优化和信号测量，为宽频、高精度、大范围的动态应变和声信号测量提供了有效解决途径。