Metallurgical Aspects of Ni-Coating and High Temperature Treatments for FBG Spectrum Regeneration.

The structural integrity of mechanical components is assessed by FBG sensors in many industrial fields. The FBG sensor has a relevant application at very high or low temperatures. To avoid the variability of the reflected spectrum and the mechanical properties degradation of the FBG sensor, metal coatings have been used to guarantee the grating's integrity in extreme temperature environments.

FBG Spectrum Regeneration by Ni-Coating and High-Temperature Treatment.

FBG sensors are used in many scientific and industrial fields for assessing the structural integrity of mechanical components and in very high (above 600 °C) or very low (cryogenic) temperature applications. The main concerns with the use of such sensors in applications involving extreme temperatures are related partly to the instability of the reflected spectrum, which tends to dissolve into the noise floor, and partly to the degradation of the mechanical properties of the optical fiber, which tends to worsen the inherent brittleness. All of this raises the need for a robust nickel protective coating to ensure the grating's integrity in high-temperature environments.

Critical Issues of Double-Metal Layer Coating on FBG for Applications at High Temperatures.

Use of fiber Bragg gratings (FBGs) to monitor high temperature (HT) applications is of great interest to the research community. Standard commercial FBGs can operate up to 600 ∘ C. For applications beyond that value, specific processing of the FBGs must be adopted to allow the grating not to deteriorate.