This relates to a dosimeter including a light source capable of generating a light beam, an optical coupler-splitter, a radio-sensitive optical fiber, a first photodetector arranged to record a power measurement of the light beam transmitted through the radio-sensitive optical fiber, a reference optical arm, a second photodetector arranged to record a reference power measurement of the light beam transmitted through the reference optical arm, and an electronic system configured to extract a differential radiation induced attenuation measurement in the radio-sensitive optical fiber with respect to the reference optical arm. The light beam is non-polarized or depolarized, or, respectively, the light beam is polarized and the radio-sensitive optical fiber is a polarization-maintaining fiber.