Optical fiber gratings for structural health monitoring in high-temperature environments

Fiber gratings are proving to provide versatile discrete sensor elements for structural health monitoring systems. For example, they outperform traditional resistive foil strain gages in terms of temperature resistance as well as multiplexing capability, relative ease of installation, electromagnetic interference immunity and electrical passivity. However, the fabrication method and post-fabrication processing influences both performance and survivability in extreme temperature environments. In this paper, we compare the performance and survivability when making strain measurements at elevated temperatures for a range of fabrication and processing conditions such as UV-laser and electric-arc writing and post-fabrication annealing. The optimum method or process will depend on the application temperatures (e.g., up to 300°C, 600°C or 1000°C), and times at these temperatures. As well, other sensing requirements, including the number of sensors, measurand and sensitivity may influence the grating choice (short or long period).

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