Abstract

There has been considerable interest in thulium-doped fiber amplifiers (TDFAs) for the S-band (1450-1530 mn) as a natural bandwidth extension in high-capacity WDM systems. Fluoride-based ZBLAN, the most efficient platform for S- band TDFAs, has the main disadvantage of host glass incompatibility with standard silica fibers and the resulting difficulty in fusion splicing, as well as suffering from hygroscopicity and mechanical and reliability problems. A reduced phonon energy silica-based host would resolve these problems. A previous work reported the development of a thulium-doped silica fiber with lùgli alumina content for reduced maximum phonon energy and resultant increased gain in the S-band when pumped at 1060 mn [1], In tins work we investigate for the first time the distributed gain of the silica-based TDFA using coherent optical frequency domain reflectometry (COFDR). COFDR results are being used to verify the numerical model and to provide accmate values for the required spectroscopic parameters for Tm-doped aluminosilicate fibers, a prerequisite for further progress in silica-based TDFA development. The obtained results will also be useful for applications of silicate TDFs for amplification in the 800 mn band and in lùgli-power 800 mn upconversion fiber lasers, as proposed recently in connection with sensitization of thulium by ytterbium [2].

© 2007 IEEE