Development of regenerated fiber Bragg grating sensors with long-term stability

The effect of annealing cycle on regeneration efficiency was investigated through isothermal treatments between 700 and 1000 degrees C. We determined an inverse relationship between the recovery rate of the peak reflectivity and temperature. A regeneration efficiency of 85.2% and long-term stability at 1000 degrees C for 500 hours were achieved via a slow regeneration process. Thermal sensors developed by isothermal regeneration were determined to be reliable up to 1000 degrees C (+/- 2 degrees C). Experimental findings suggest the involvement of both diffusion related phenomena and stress variation through densification of the fiber core in type-I FBG during the thermal regeneration process. (C) 2016 Optical Society of America