Using optical frequency-domain reflectometry to reveal the gain distribution and allow us to optimize a thulium-doped fiber amplifier, we have demonstrated 18-dB gain by employing only 5 m of a 2000-parts-in- 10<sup>6</sup> –Tm-doped fiber pumped with 145 mW of power at dual wavelengths of 800 and 1050 nm. The role of the 800-nm pump, which by itself does not permit population inversion, was clearly observed experimentally.
© 2003 Optical Society of America
A. S. L. Gomes, M. T. Carvalho, M. L. Sundheimer, C. J. A. Bastos-Filho, J. F. Martins-Filho, J. P. Von der Weid, and W. Margulis, "Low-pump-power, short-fiber copropagating dual-pumped (800 and 1050nm) thulium-doped fiber amplifier," Opt. Lett. 28, 334-336 (2003)