Improved radiation resistance of an Er-doped silica fiber by a preform pretreatment method.

We report a novel pretreatment method to improve the radiation resistance of Er-doped fiber (EDF). The processing object of this method is EDF preform, and the pretreatment processing involves three steps: deuterium loading, pre-irradiation, and thermal annealing. The effects of pretreatment conditions on the optical loss, gain performance, and radiation resistance of EDF were systematically studied. The relevant mechanisms were revealed using Fourier transform infrared (FTIR), radiation-induced absorption (RIA), and electron paramagnetic resonance (EPR) spectroscopies. The results show that the pretreatment can not only greatly reduce the hydroxyl content of the EDF core, but it can also effectively improve the radiation resistance of EDF. The online test results show that the gain of the commercial, pristine, and pretreated EDFs were reduced by 19.0, 4.2, and 1.3 dB, respectively, corresponding to a decrease of 68.1, 16.2, and 4.7% after 98 krad X-rays irradiation. The high vacuum experiments show that the pretreatment method can maintain long-term stable high radiation resistance. This work provides a reference for the development of high-performance radiation resistant EDFs for use in the lower, middle, and geosynchronous earth orbit.