Gamma radiation effect on the fiber Fabry-Perot interference sensor

The variation of thermo-optic coefficient caused by gamma irradiation is investigated for the fiber Fabry-Perot interference (FFPI) sensor. The sensor is formed by fusing fibers with different core diameters, and its thermo-optic coefficient is measured during irradiation up to doses higher than 1 MGy. The method used to measure the thermooptic coefficient shows excellent agreement with Sellmeier equation with a difference of only 0.2%. Experiments show that the relative change of thermo-optic coefficient increases only by 2.1% and saturates at a total dose of 300 kGy, which suggests that the fiber FFPI sensor is suitable for use in harsh gamma radiation environments.