575818.fig.004a
(a)
575818.fig.004b
(b)
Figure 4: Fluorescence spectra of 1000 ppm Er-doped 2S2G glasses pumped at 804 nm. (a) 1.5 and 1.7 μm emissions and (b) 4.5 μm emission from a bulk glass, 20 cm of a 400 μm diameter monoindex fiber, and 20 cm of a 60 μm core diameter double index fiber [24].