Abstract
The total flux of upconversion spectral power distributions was quantitatively investigated for erbium-doped fibers with different ion concentrations using an integrating sphere. The dependence of gain on the signal output power at 1530 nm was measured. The small-signal gain decreased with increasing Er3+ ion concentration and the gain decreased with increasing signal power. Evidence of signal laser contribution to green upconversion was observed. It was found that the contribution of the signal laser to the green upconversion decreased with increasing Er3+ ion concentration.