An experimental and theoretical study of the influence of Cerenkov radiation on optical fiber X-ray sensors

•The PDD curves of capped and uncapped fiber X-ray sensors are almost opposite.•A theoretical model was established to explain the different trend of PDD curves.•The peak or valley of the curves of Cerenkov radiation are at a depth of 1.5 cm. The use of optical fiber X-ray sensors is of great significance in X-ray detection. To reduce the influence of background noise attributed to sources such as Cerenkov radiation, the response of a plain (no scintillator material added) optical fiber to the X-ray radiation is investigated. The percentage dose-depth (PDD) of plain optical fibers with and without visible light blocking end caps are calculated and are clearly different. The leakage of Cerenkov radiation and presence of Compton scattering from water into the sensing probe is considered as the reason for the difference. A theoretical model to explain the difference is proposed. The experimental results fit well to the theoretical expectation.