Nowadays, long distance optical fibre transmission systems use polarization diversity multiplexed signals to enhance transmission performance. Distributed acoustic sensors (DAS) use the same propagation medium, i.e., single mode optical fibre, and aim at comparable targets such as covering the highest distance with the best signal quality. In the case of sensors, a noiseless transmission enables us to monitor a large quantity of mechanical events along the fibre. This paper aims at extending the perspectives of DAS systems with regard to technology breakthroughs introduced in long haul transmission systems over the past decade. We recently developed a sensor interrogation method based on coherent phase-sensitive optical time domain reflectometry (ϕ-OTDR), with dual polarization multiplexing at the transmitter and polarization diversity at the receiver. We name this technique coherent-MIMO sensing. A study is performed from a dual-polarization numerical model to compare several sensor interrogation techniques, including coherent-MIMO. We demonstrate that dual-polarization probing of a fibre sensor makes it insensitive to polarization effects, decreases the risks of false alarms and thus strongly enhances its sensitivity. The simulations results are validated with an experiment, and finally quantitative data are given on the performance increase enabled by coherent-MIMO sensing.

中文翻译：

---

引入相干MIMO感测，这是一种针对ϕ-OTDR的衰落，回弹性，偏振无关的方法。

如今，长距离光纤传输系统使用偏振分集复用信号来增强传输性能。分布式声学传感器（DAS）使用相同的传播介质，即单模光纤，并瞄准可比较的目标，例如以最佳信号质量覆盖最大距离。就传感器而言，无噪音传输使我们能够监控光纤上的大量机械事件。本文旨在就过去十年在远程传输系统中引入的技术突破扩展DAS系统的观点。我们最近开发了一种基于相干相敏光时域反射仪（ϕ-OTDR），在发射机处进行双极化复用，在接收机处进行极化分集。我们将此技术命名为相干MIMO感测。从双极化数值模型进行了研究，以比较几种传感器询问技术，包括相干MIMO。我们证明了光纤传感器的双偏振探测使其对偏振效应不敏感，降低了误报的风险，从而极大地提高了其灵敏度。通过实验验证了仿真结果，最后给出了有关相干MIMO传感实现的性能提升的定量数据。