Distributed Optical Fiber-Based Dosimetry With Optical Frequency Domain Reflectometry

We demonstrate a real-time high-spatial-resolution (3 cm) ionizing dose 2-D mapping sensor achieved by analyzing a phosphorus-doped silica-based optical fiber with a Rayleigh-optical frequency domain reflectometry (R-OFDR) interrogator. The dose is monitored through the radiation-induced attenuation (RIA) around 1550 nm measured on the OFDR traces. This study aims at studying the sensor performances and assessing its dose mapping capabilities. The RIA spectrum from the P-doped fiber is first characterized and the fiber radiation sensitivity is calibrated by evaluating the dose rate. Then, the dose-rate dependence (from 10 mGy/s up to 4 Gy/s) of the RIA levels and kinetics has been investigated up to a cumulated dose of 2 kGy (SiO2) . The achievable spatial RIA resolution with the R-OFDR is equal to 3 cm for precise distributed measurements. Finally, a 2-D square mapping of our X-ray beam has been performed during irradiation with a 10-s acquisition period. These results highlight the significance of distributed and active R-OFDR dosimetry for doses up to 2 kGy, as well as beam shape sensing with high spatial resolution.