Radiation and temperature effect of fiber Bragg grating sensor under Co-60 irradiation

Highlights: • Study of the effect of repeated irradiation on the thermo-optical coefficient of fiber Bragg grating. • Development of a mathematical algorithm for the temperature compensation of the fiber Bragg grating dosimeter. • Study of the effect of cumulative dose from Co-60 gamma rays on Bragg wavelength shift. This work aims to develop and characterize a mathematical algorithm for the temperature compensation of the fiber Bragg grating dosimeter and study of the effect of cumulative radiation dose on the Bragg wavelength shift (BWS). Studies on the BWS and the influence on the thermo-optic response coefficient of FBGs caused by the Co-60 gamma irradiation are performed. The BWS shows a linear dependence on temperature, and the inherent thermo-optic coefficients of the FBGs range from 10.1 to 24.0 pm/°C. The thermo-optic coefficient of FBGs is measured immediately after every 2-h irradiation. It turns out that the thermo-optic coefficient is not affected by the cumulative radiation dose and the fluctuation caused by radiation is under 2.2%. The BWS caused by 6.75 kGy gamma rays in 15 h shows a linear increase after correcting the interference of temperature. The radiation-induced coefficient is 5.18 pm/kGy and the lowest cumulative dose detection limit can be achieved at 116 Gy, which is assessed in the specific situation. The study of wavelength recovery after 3.375 kGy irradiation shows that the BWS can be recovered by around 7 pm from the 15 pm redshift, which indicates that the damage caused by the 3.5-h irradiation can be partly self-healed. This study shows the application feasibility of FBG as an online and remote radiation dosimeter.