Mode Division Multiplexing for Distributed Sensing

在光纤中，传统上使用单模操作来执行感测，技术上表示为单模光纤（SMF）。这种操作大大降低了传感器信号处理的复杂性，但同时也大大限制了光纤传感器和传感系统的能力。在这个项目中，自适应光学方法与模分复用技术相结合，大大扩展了光纤传感器网络的整体传感能力，并减少了10至100的因素，每个传感器的成本。该项目中研究的新型模分复用（MDM）传感技术可以影响广泛的关键传感应用和数据通信，并将实现大规模低成本基础设施监控以及灵活和超高数据速率的互联网通信。从技术上讲，该项目旨在开发一种用于分布式传感的MDM传感器网络。该传感器网络的最关键元件是自适应光学组件，其可以：1）在多模光纤中实现高度选择性的模式激发，以及2）将询问信号动态地路由到不同的传感器子网络。具体来说，两个多模态传感器网络将被证明：一个准分布式的温度/应变传感，和一个完全分布式的光时域反射传感。我们的目标是证明，它是可能的，集成多个有效的传感器在一个单一的光纤，利用多模操作。第二个目标是确认模分复用与最先进的复用方法的完全兼容性。实现这两个目标将表明，通过采用利用M个模式的光纤模式，可以将任何现有光纤传感器网络的整体感测能力提高M倍。虽然该项目将限于双模式操作（M=2），这将导致给定光纤上可用的传感器密度加倍，但完全可以预期，所开发的原理将适用于M高达10至100的情况，对应于传感器密度增加十倍或百倍。

In optical fibers, sensing is traditionally carried out using a single mode operation, technically denoted as Single Mode Fibers (SMF). This operation greatly reduces the complexity of sensor signal processing, but at the same time, significantly limits the capabilities of fiber sensors and sensing systems. In this project, adaptive optics methodologies are employed in conjunction with mode division multiplexing techniques to greatly expand the overall sensing capacity of fiber optics sensor networks and to reduce their per-sensor-cost by a factor of 10 to 100. The novel mode division multiplexing, or MDM, sensing technology investigated in this project can impact a wide array of critical sensing applications and data communication, and will enable large-scale low-cost infrastructure monitoring as well as flexible and ultra-high-data-rate internet communications. Technically, this project aims to develop a first-of-its-kind MDM sensor network for distributed sensing. The most critical element of this sensor network is an adaptive optical component that can: 1) achieve highly selective mode excitation in a multi mode fiber, and 2) dynamically route the interrogation signals towards different sensor sub-networks. Specifically, two multi modal sensor networks will be demonstrated: a quasi-distributed one for temperature/strain sensing, and a fully distributed one for optical time-domain reflectometry sensing. The goal is to demonstrate that it is possible to integrate multiple effective sensors in a single fiber by exploiting the multi mode operation. A secondary goal is to confirm the full compatibility of mode division multiplexing with state-of-the-art multiplexing methods. Accomplishing these two goals will suggest that by employing fiber modes utilizing M modes, one can increase the overall sensing capacity of any existing fiber sensor network by a factor of M. While the project will be limited to two-mode operation (M=2), which will lead to the doubling of the sensors density available on a given fiber, it is fully expected that the developed principles will be applicable to cases with M as large as 10 to 100, corresponding to ten-fold or hundred-fold increase in sensor densities.