We demonstrate, for the first time to our knowledge, the strong recovery of the optical-optical slope efficiency of gamma-ray-irradiated Tm-doped fiber under 793 nm laser diode (LD) pumping. The fiber optical-optical slope efficiency, the fiber cladding absorption spectra, and the fluorescence spectra of the Tm-doped fiber before and after 500 Gy gamma-ray irradiation have been measured for comparison. It is found that the fiber optical-optical slope efficiency had significant degradation from 56.3% to 26.7% after irradiation and recovered to 40.8% after 15 h pump bleaching. Based on comparative analysis of fiber cladding absorption spectra among pristine fiber, irradiation, and bleaching, the reasons for the strong recovery have also been discussed.

Yb-doped double-clad fibers are prepared through a conventional modified chemical-vapor deposition technique and solution doping method: each fiber contains a core of around 10 μm in diameter. These fibers are divided into groups under 60Co γ radiations of different doses, and we investigate the fiber absorption spectra and laser spectral properties before and after irradiation. Experimental results show that with increasing the irradiation dose the absorption of the fiber after irradiation increases significantly in the visible region, we believe that the enhancement of optical fiber absorption in the visible region may be due to the color center defects existing already in the fiber (such ODC (Ⅱ)) and the color center defects produced by the irradiation (E'center, POR and Yb2+ions). We also analyze slope efficiencies, bare efficiencies, and transmission characteristics of the fiber before and after laser irradiation. Finally, we use the power-law to fit the radiation-induced losses of the fiber under different radiation doses, and the results obtained in this paper provide a theoretical basis for studying the anti-radiation of optical fibers.