Effect of Drawing Conditions on Optical Properties of Bismuth-Doped High-GeO<sub>2</sub>–SiO<sub>2</sub> Fibers
Sergei Firstov, Andrei E. Levchenko, Aleksandr Kharakhordin, Aleksandr Khegai, Sergey Alyshev, Mikhail Melkumov, V. F. Khopin, Alexey Lobanov, Alexey Guryanov
Abstract
The effect of drawing conditions on the optical properties of the bismuth-doped high-germania-glass core fibers has been studied. It was found that the gain characteristics of these fibers become better with the increase of the drawing speed from 10 to 100 m/min. The small-signal absorption spectra of the Bi-doped fibers obtained at drawing speeds lower than 1 m/min are characterized by a high level of the unsaturable loss and the presence of an unstructured band situated within a wavelength region of 1100 - 1250 nm. The variation of drawing temperature ranging from 1770 to 1830 °C almost did not affect the optical properties of the fibers studied. It was shown that an optimization of the drawing parameters can significantly increase the performance of the developed bismuth-doped fiber lasers.