High-Temperature Fiber Grating Technologies for In Situ Interrogation of Damage States in Structural Materials

Fiber optic gratings are critical components for advanced multi-point sensor systems that can be used to assess the remaining lifetime of components in highly complex mechanical systems. . Standard gratings, however, degrade at temperatures below the melting point of glass. Thus, the gratings lose their sensing capability in thermally harsh environments. To respond to the Air Force's need for in situ harsh environment sensing technologies to interrogate material and damage states for engine, airframe, and hot structure components, Intelligent Fiber Optic Systems (IFOS) is proposing a grating writing method to significantly extend the operating range of grating-based sensors to temperatures close to the melting point of glass. IFOS will develop a robust high-temperature grating fabrication process and design a multi-point sensor system to demonstrate survivability and operation at high temperatures. The system, which will include a compact interrogator, can simultaneously measure strain, vibration, acceleration, and temperature. The system can be deployed for physical as well as chemical and bio-agents sensing, and is thus applicable to gases in combustion environments and high temperature spectroscopy. It allows for distributed and remote measurement in harsh environments. Sensor readout is accomplished at extremely high speed and high resolution using secure fiber optic links.