外部调制光相干域分布式光纤传感技术研究

By manipulation in time-domain, frequency-domain, or coherence-domain, the distributed fiber-optic sensing technology realizes spatially resolved measurement along the optical path, and obtains the distribution information of measurands. The proposer of this research proposal, when studying and working in the University of Tokyo, jointly created and developed a coherence domain distributed fiber-optic sensing technique by controlling the coherence of continuous lightwave to realize spatial resolving, which is in the world-leading position in performance such as spatial resolution and measurement speed. Utilizing direct frequency modulation of the laser source, further improvement on the performance of the technique is limited by the property of available rapidly broadband-tunable laser source. Based upon the world-leading developed technique, this proposal introduces two novel external modulation methods. One adopts external frequency modulation, and realizes spatial resolving by adjusting the parameters of the frequency modulation. The other uses external intensity modulation by pseudo-random binary sequence (PRBS) signal where spatial resolving is done by delaying the modulation signal. In this way, the performance of the coherence domain distributed fiber-optic sensing technology can be enhanced greatly by breaking the limitation in the tuning property of the laser source. This technology can provide an efficient tool for the maintenance of fiber-to-the-home links, and diagnosis of fiber-optic devices, which are thought an industry-wide headache for optical fiber communication industry, and can be used widely in smart materials and structural health monitoring.

分布式光纤传感技术运用时间域、频率域或相干域的操作，实现沿着光路的空间位置的分辨，获取被测量的分布信息。本项目申请者在日本东京大学学习和任教期间，共同开创和发展了通过控制连续光的相干特性而实现位置分辨的相干域分布式光纤传感技术，目前在空间分辨率和测量速率等性能上处于世界领先地位。该技术由于采用光源频率直接调制，其性能的进一步提高受限于市场上可获得的快速宽带可调谐激光器的性能。本项目在原有技术的基础上，导入两种新型的外部调制方法。一种采用外部频率调制，通过改变频率调制参数进行位置分辨；另一种采用伪随机二进制序列（PRBS）外部强度调制，通过电信号的延迟进行位置分辨。由此突破光源调谐性能的限制，大幅提高相干域分布式光纤传感技术的性能。这种技术不仅能够对光纤到户通信线路的维修、光纤器件的诊断等光通信业界难题的解决，提供有效的方法，而且在灵巧材料的实现以及结构安全监视等方面，都有着广泛的应用。

项目研究计划执行过程中，我们已经充分完成了项目计划的外部调制OCDR法、采用外部调制法的基于布里渊散射的分布式光纤传感技术，通过四波混频等光信号处理方法的扫频扩频方案将外部调制频率增加到67GHz，在光相干域反射仪技术中实现了1.9 mm的空间分辨率，在基于布里渊散射的分布式光纤传感技术中实现有效传感点数的倍增。项目指标超过预期，主要原因是在研究过程中我们探索并实现了包括注入锁定法和扩大外部扫频范围的非线性光学信号处理技术方案，结合原有外部调制法技术方案得到了优异的空间分辨率性能。项目实施过程中，我们也做了开放性的研究拓展，针对光频域反射仪（OFDR）技术应用实现线性扫频100GHz的光源，在2km测量距离下实现1.1mm超高空间分辨率。项目执行过程中，总计发表论文38篇，其中SCI论文12篇，申请专利28项，培养博士研究生5人。