A multiquantum-dot-doped fiber amplifier with characteristics of broadband, flat gain, and low noise

Doped with PbSe nanocrystals of different sizes, a multiquantum-dot-doped fiber amplifier (MQDFA) is proposed. Performance of the MQDFA is simulated by solving light-propagation equations and rate equations for a three-level system, and by applying superposed emission-absorption cross sections of the quantum dots (QDs). Pumped with 980 nm, this proposed MQDFA has characteristics of broader band, flatter gain, and lower noise than those of the erbium-doped fiber amplifiers at present. There is evidence to show that two factors, i.e., the equivalent Stokes shifts and the full wave at half maximum of the superposed spectra, dominate the performances of the MQDFA. Also, the equivalent Stokes shift and the FWHM are tunable by adopting the QDs in different sizes and choosing the doped number available. It is expected that such a MQDFA may be able to cover the all waveband in telecommunications if it is optimized on the doped number, sizes, and doped concentrations of the QDs.