Improved gain performance of high concentration Er/sup 3+/-Yb/sup 3+/-codoped phosphate fiber amplifier

The rate equations and power evolution equations of erbium/ytterbium codoped phosphate fiber amplifiers are solved numerically and its results are compared with measured data in literature. Based on the numerical analysis, optimal erbium and ytterbium codoping concentrations are supposed, and with a pump power of 224 mW and a fiber length of 3.6 cm, the internal gain of 31.0 dB and gain per unit length of 8.6 dB/cm may be achieved in the fiber with the optimal codoping concentrations.