Infrared radiation Induced attenuation of radiation sensitive optical fibers: influence of temperature and modal propagation

We investigate the X-ray (40 keV) and γ-ray (1.2 MeV) radiation responses of three different radiation sensitive Optical Fibers (OFs) up to 100 Gy(SiO$_2$). In particular, we study the Radiation Induced Attenuation (RIA) in the Near Infrared domain (NIR) for single mode OFs doped with Phosphorus (P), Aluminum (Al) and Phosphorus/Cerium (PCe) in their cores at three temperatures up to 50 °C. RIA levels and kinetics strongly depend on the operating wavelength and fiber composition. For both P and PCe-doped fibers, the P1 defects are the main contributors to the RIA, with Ce-codoping inducing a decrease of radiation sensitivity. For the Al-doped fiber, no specific absorption bands can be discriminated in the NIR. Both X- and γ-rays lead to the same RIA levels and kinetics. The RIA spectral dependences on dose and temperature highlight the potential of the three investigated fibers for radiation detection and dosimetry. To better discuss the properties of point defects responsible for the NIR RIA, we analyze how the fundamental mode propagation influences the RIA spectra of each fiber type. By reasonably assuming that the core RIA exceeds largely the cladding RIA and by calculating the mode Confinement Factor (CF), the RIA spectra of the core material are reconstructed and the spectral characteristics of defects are discussed for each type of fibers.