Modeling erbium–thulium-co-doped fiber amplifier for 1400–1650 nm band

We present numerical models of tri-valence erbium ion and thulium ion-co-doped fiber amplifiers pumped by 800-nm and 980-nm lasers. The rate and power propagation equations of the models are numerically solved to analyze the gain as a function of co-doping concentrations, fiber length and signal wavelength. The results reveal that with 800-nm or 980-nm pump, gain competition exists between 1470- and 1530-nm bands, which may arise from the pump absorption competition and complicated energy transfer between the two types of active ions, and the results further show that the gain spectra may cover 305 nm (1375–1680 nm) for 800-nm pump and 160 nm (1400–1560 nm) for 980-nm pump. The doping concentrations and fiber length may be tuned to reduce the ripple of the gain spectra.