Radiation Resistant Er-Doped Fibers: Optimization of Pump Wavelength

H-free and H-loaded pieces of a carbon-coated erbium-doped fiber (EDF) are gamma-irradiated to doses in the range 0.1-10 kGy. In three months after the irradiation, optical loss spectra and lasing efficiency of the fibers are studied. It is found that the slope efficiency of a laser based on an irradiated EDF quickly grows under the action of pumping at the wavelength of 980 nm, owing to photobleaching of radiation-induced color centers. Photobleaching is found to be much more efficient in H₂-loaded EDFs. No photobleaching occurs with pumping at 1480 nm. Pumping at 980 nm is argued to ensure a sufficiently long service life of H₂-loaded EDFs in space, much longer than in the case of pumping at 1480 nm.