Reliability of optical fiber Bragg grating sensors at elevated temperature

The mechanical and optical reliability of two types of stripped and polyimide recoated optical fiber Bragg gratings at operating temperatures up to 250 °C was demonstrated. Mechanical strength is critical for Bragg gratings stripped and recoated for UV radiation. For long-term monitoring, BG proof tests can eliminate samples weakened during manufacturing. Drift in grating wavelength and reflectivity with time can be reduced by properly pre-annealing the gratings prior to their application. Changing any fabrication parameter in production may considerably change model parameters and lifetime predictions.