Temperature Dependence of Low-Dose Radiation-Induced Attenuation of Germanium-Doped Optical Fiber at Infrared Wavelengths

Ge-doped optical fibers (OFs) are considered radiation-tolerant waveguides. Even if their transmission in the infrared (IR) domain is degraded under irradiation, for most of the applications, their radiation-induced attenuation (RIA) remains acceptable. Space harsh environment is characterized by low dose and dose-rate constraints meaning that germanosilicate fibers are often employed for data links. However, the temperature can largely vary in space and is known to impact the RIA levels and kinetics. We studied here systematically the combined temperature and radiation effects induced on the transmission, at the telecom wavelengths, of a Ge-doped fiber, between -80 degrees C and 80 degrees C up to a total ionizing dose (TID) of 10 kGy(SiO2)-1 Mrad. Our measurements highlight larger RIA levels at low temperatures than at room temperature (RT). At our highest TID, it increases by a factor of similar to 40 and similar to 20, respectively, at 1310 and 1550 nm, when the irradiation is performed at -80 degrees C instead of RT. A model is reported to study the activation energy of the radiation-induced point defects responsible for the IR-RIA. This simple model could help in predicting the fiber vulnerability for various mission profiles.