Absorption and emission cross section of Er(3+) doped silica fibers

A detailed set of measurements is presented on determining the emission and absorption cross sections of Er(3 ) doped fibers for the (4) < e1 > I < /e1 > (13/2)- > (4) < e1 > I < /e1 > (15/2) transition. Two techniques are employed: the Fuchtbauer-Ladenberg analysis, based on spectroscopic data, and a more direct technique involving optical saturation of the transition. The cross sections, and in particular their ratio, are significantly different for the two techniques. Possible reasons for this are discussed, and it is concluded that the Fuchtbauer-Ladenberg approach is inappropriate in this situation