Gamma-radiation impact on temperature and RH sensitivity of FBGs in a few-mode polymer CYTOP fiber

We characterize a fiber Bragg grating (FBG) inscribed in a few-mode polymer CYTOP® fiber for temperature and relative humidity (RH) response before and after gamma radiation treatment. The results demonstrate strong rise of RH sensitivity: from 13.3 pm/%RH for the pristine FBG up to 56.8 pm/%RH after receiving 520 kGy gamma radiation dose. Temperature response also becomes stronger and moreover, demonstrates change of sign: from 19.6 pm/℃ for the pristine case down to -38.9 pm/℃ after irradiation. The results show the possibility of temperature and RH response adjustment by gamma radiation, and suggest the existence of an optimal radiation dose which can eliminate temperature sensitivity.
This work has been sponsored by Fonds De La Recherche Scientifique – FRNS (T.0163.19 "RADPOF"). The research leading to these results has also received funding from the Horizon 2020 programme of the European Union (Marie Skłodowska-Curie Actions - Individual Fellowships) under REA grant agreement No.844618 (project POSPORI) and the Cyprus Research and Innovation Foundation (EXCELLENCE/0918/0324 "T-Sense").