基于相位生成载波算法的混合型光纤传感系统的研究

On account of exploring the application of optical fiber sensing technology in the field of oil and gas exploration, the project creatively proposes a hybrid optical fiber sensing system based on a phase-generated-carrier algorithm to meet requirements of high fidelity, high signal to noise ratio and high resolution of geophysical equipment. Because of the novel architecture, the hybrid system has the advantages of high signal to noise ratio and multi sensing nodes, which compromises the merits of distributed acoustic sensing technology and fiber laser sensing technology. The project intends to develop a phase generated carrier demodulation technique with a character of high rate, quasi-parallel and large capacity of mixed data. In addition, a noise and crosstalk model of the hybrid system will be established. On the other hand, through study on the characteristics of Rayleigh scattering light in the fiber, the effects of coherent Rayleigh scattering polarization fading and interference fading will be eliminated. There are two key scientific problems in the hybrid system, i.e., signal fading in distributed acoustic sensing technology and the characteristics of noise and crosstalk of the system, the research of which will be carried out in the project.

本项目以光纤传感技术在油气物探领域的应用为背景，瞄准物探装备高保真度、高信噪比和高分辨率的“三高”应用需求，创新性提出一种基于相位生成载波算法的混合光纤传感系统。该系统融合了分布式声传感技术和光纤激光传感技术两种技术，具有信噪比高、节点数多等优势。项目拟开发高速、准并行和大容量数据混合型的相位生成载波解调技术，搭建系统噪声和串扰模型；通过研究光纤中瑞利散射光的特性，消除混合系统中相干瑞利散射光偏振衰落和干涉衰落的影响；对于混合系统中分布式声传感技术的信号衰落问题、混合系统的噪声和串扰特性等关键问题开展研究。

随着地震勘探技术的发展，对地质结构的描述向着更深、更小、更薄的方向延伸，进而对地震勘探仪器的要求越来越高，即高度保持地震波的真振幅和尽量提高地震资料的信噪比和分辨率。本项目通过整合光纤激光传感和分布式光纤声传感，开展基于相位生成载波算法的混合型光纤传感系统的研究，既具有分布式声传感技术高空间分辨率，海量信号道检测的优点，同时兼顾了分布反馈式光纤激光器传感技术高灵敏度的特点，采用高速、大容量数据的准并行PGC解调算法实现的实时相位解调，克服数据离线处理导致的测量结果实效性差的不足。利用相位解调技术和多通道加权平均的方法来解决DAS技术中存在的干涉相消难点问题，同时降低了分布式光纤声传感技术中通道间噪声水平起伏波动大的问题。搭建了基于相位生成载波算法的实时混合型光纤传感系统样机，样机指标如下：传感距离10.1km，信噪比61.4dB，相位实时刷新率0.1s，测量频率范围1Hz-2.499kHz，动态范围120dB@100Hz。针对野外应用便携性要求，通过优化光学模块和电学模块，实现了国际上目前报道的最低功耗和最小尺寸的解调模块，并在此基础上在大庆油田，河北涿州，长庆油田，青海油田，海南三亚等地开展了开展了浅层地表成像，垂直地震测井，海洋物理，智慧校园，周界安防等领域的应用探索，充分验证了该系统的可靠性和有效性。