Packaging of surface relief fiber Bragg gratings for use as strain sensors at high temperature

In this paper, we report the development of a new bonding agent and method for the surface mounting of optical fiber Bragg grating (FBG) strain and temperature sensors for use in high temperature environments - where there is a presence of water, moisture, dust, susceptibility to corrosion and/or elevated temperatures up to 800°C. To ensure a stable reflectivity response of FBGs and their survival at elevated temperatures, we are using surface relief fiber Bragg gratings (SR-FBG). These gratings, instead of being written in the core of a photosensitive or hydrogen-loaded fiber, are formed by introducing a periodic surface relief - through photolithographic and etching processes - in the cladding above the core. Samples of SR-FBGs were successfully encapsulated and mounted onto metal shims. The packaged sensors displayed a linear response with temperature and a sensitivity factor of 11pm/°C.