Compact multimode pumped erbium-doped phosphate fiber amplifiers

The performance of compact multimode pumped erbiumdoped phosphate fiber amplifiers is presented. A fiber amplifier with a small signal net gain of 41 dB at 1535 nm and 21 dB over the full C-band is demonstrated using a newly developed 8-cm-long erbium-doped phosphate fiber excited with a 1-W, 975-nm multimode laser diode. A theoretical model is developed for the multimode pumped amplifier based on modified rate equations and an effective beam propagation method. Close agreement between experimental and modeling results is observed.