Résumé
We investigate the growth kinetics of the radiation induced attenuation of 25-km long commercial Ge-doped optical fiber coils during a long-term gamma irradiation at different very low dose rates. Moreover, X-ray irradiation accelerated tests were also performed allowing a total comparison at room temperature over 6-decades of dose rates, from 19.8 mGy(SiO 2 )/h to 13.8 kGy(SiO 2 )/h. We confirm that the RIA levels increase with the dose rate for a given TID, with level differences up to a factor of 10 comparing our lowest and highest dose rates. Accelerated tests lead to higher RIA, and therefore have to be considered as "worst-case" studies for qualification irradiation campaign. Then, we investigate how ambient light can influence the RIA kinetics of our samples, emphasizing the importance of controlling this parameter to ensure the most consistent irradiation tests possible. Results show that this parameter can be negligible for very low dose rate (~20 mGy/h) tests but must be handled for accelerated tests, especially if optical fibers are exposed to the light for a long time. Finally, we perform several Monte-Carlo simulations to estimate how the TID is indirectly deposited by photons in the cores of our very long fiber coils.