Double-clad Er-doped fibers highly doped with aluminum (up to 3 mol.%) and fluorine (up to 1.5 wt.%) have been fabricated and studied. The fibers have a core numerical aperture of approximately 0.055, which allowed us to achieve a single-mode propagation regime for a fiber core diameter of 35 µ m. The possibility of increasing the pump-to-signal conversion efficiency in the L-band using the developed double-clad Er-doped fibers was demonstrated. Utilization of the F–GeO 2 –Al 2 O 3 –SiO 2 –Er fiber together with a P 2 O 5 –Al 2 O 3 –SiO 2 –Er fiber was found to be promising for single-frequency amplifiers because the fibers have negligible overlap of the stimulated Brillouin scattering gain. This feature allowed us to build a cascaded double-clad Er-doped fiber amplifier (two Er-doped fibers of different types were spliced one by one) with a threshold of stimulated Brillouin scattering greater...

中文翻译：

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Al 2 O 3 -SiO 2芯高度掺氟的包层泵浦掺Er（无Yb）纤维

已经制造和研究了高度掺杂有铝（最高3 mol。％）和氟（最高1.5 wt。％）的双掺Er光纤。光纤的纤芯数值孔径约为0.055，这使我们能够在纤芯直径为35 µm的情况下实现单模传播。证明了使用开发的双包层掺Er光纤在L波段提高泵浦信号转换效率的可能性。人们发现，将F–GeO 2 –Al 2 O 3 –SiO 2 –Er纤维与P 2 O 5 –Al 2 O 3 –SiO 2 –Er纤维一起使用对于单频放大器是有前途的受激布里渊散射增益的可忽略的重叠。