Spectral Multiplexing of Fiber Bragg Grating Sensors for Low-Power Optical Sensor Networks

在大型复杂结构系统的整个使用寿命期间监测其结构完整性和性能是非常重要的。在役监测可以提高结构的安全性，减少维修的停机时间。本研究的目的是推导、实现和演示一种低功耗、基于光纤的应变传感器网络，该网络可以扩展到大量传感器，并应用于大型机械和航空航天结构系统的高速测试。低功耗、高数据采集速率传感器网络将在复合材料结构的两个关键应用中进行评估。首先，对复合材料汽车结构进行碰撞测试，进行事故生存能力分析，将更好地了解这些材料在碰撞过程中的行为和吸收能量的方式。在汽车结构中部署大量传感器的传感器网络将允许对碰撞过程中材料的动态失效进行详细分析。其次，将传感器网络应用于复合材料机体结构的雷击试验。由于复合材料固有的低电导率，雷击给飞机结构中的碳复合材料带来了很大的问题，当转换后的闪电电磁能量通过材料传播时，会导致材料的严重损坏。高密度传感器网络将允许雷击特性和所造成的材料损坏之间的详细关联。一种基于测量光纤光栅各自光谱特性的复用光纤光栅传感器的全新方法将被推导和测试。这种多路复用策略可以扩展到大量传感器和高速数据处理，从而能够使用单个低带宽、低功耗、低成本的激光源实现大量布拉格光栅传感器的多路复用。高复用光纤布拉格光栅传感器网络中的传感器数据识别和测量算法将基于形状剖面分复用和波分复用的组合，同时结合传感器网络响应的先验知识来提高精度。这项研究的结果将是光纤布拉格光栅传感器网络的多路复用能力，其功率要求比当前系统低几个数量级，使未来的光纤布拉格光栅传感器网络能够在无线传感平台上运行。

It is important to monitor the structural integrity and performance of large, complex structural systems throughout their service life. In-service monitoring can increase the safety of the structure and reduce downtimes for repairs. The aim of this research is to derive, implement and demonstrate a low-power, optical fiber based, strain sensor network that can be scaled up to a large number of sensors and applied for high-speed testing of large mechanical and aerospace structural systems. The low-power, high data acquisition rate sensor network will be evaluated for two critical applications of composite structures. First, crash-testing of composite automotive structures for accident survivability analysis will better enable the understanding of how these materials behave and absorb energy during a crash. The implementation of the sensor network with a large number of sensors in the automotive structure will permit a detailed analysis of the dynamic failure of the materials during the crash. Second, the sensor network will be applied to lightning strike testing of composite airframe structures. Lightning strikes pose a large problem for carbon composite materials in aircraft structures due to the inherent low conductivity of composite materials, leading to significant material damage as the converted lightning electromagnetic energy propagates through the material. The high-density sensor network will permit a detailed correlation between the lightning strike properties and the resulting material damage. A fundamentally new method for multiplexing fiber Bragg grating sensors based on the measurement of their individual spectral properties will be derived and tested. This multiplexing strategy can be scaled to both a large number of sensors and high-speed data processing, enabling the capability to multiplex a large number of Bragg grating sensors using a single low-bandwidth, low-power, low-cost laser source. An algorithm for sensor data identification and measurement in highly multiplexed fiber Bragg grating sensor networks will be derived based on combined shape profile division multiplexing and wavelength division multiplexing, while incorporating prior knowledge of the sensor network responses for increased accuracy. The outcome of this research would be fiber Bragg grating sensor network multiplexing capabilities with power requirements orders of magnitude less than current systems, enabling future fiber Bragg grating sensor networks on wireless sensing platforms.