Improved gain characteristics of high concentration erbium-doped phosphate fiber amplifier

Both cooperative up-conversion and pair-induced concentration quenching of erbium-doped phosphate fiber with high doping concentration are considered for the first time in this letter. The dependence of the calculated gain on pump power is compared with measured data, and the results show that ion pair may exist in erbium-doped phosphate fiber with doping concentration of 3.8/spl times/10/sup 26/ ion/m/sup 3/. For several erbium-doped phosphate fibers with different lengths, improved gain may be obtained with higher doping concentration.