Effect of adhesives on the spectral response of Bragg gratings embedded on sapphire wafer in extreme cryogenic temperatures

Emerging fusion energy and electric aviation technologies rely on superconductors that work in extreme cryogenic environments. Fiber Bragg gratings (FBGs) have emerged as critical components in temperature profiling under such extreme environments. In this study, we characterize a temperature sensor for the superconducting dynamo-based power supply using FBGs. We studied the spectral response of FBGs at cryogenic temperatures using different bonding adhesives. Among the different cryogenic adhesives used, the FBGs bonded with Apiezon N were found to be more reliable.