International audienceA comprehensive numerical model of a thulium-doped silica-based fibre amplifiers is presented. The model is spectrally and spatially resolved and is general in terms of pumping scheme used. The application of the model for predicting the S-band amplifier performance and for optimization of amplifier parameters is shown. For optimized Tm-doped fibre with 3 H4 level lifetime of 45 ls, which is the maximum value in the Tm-doped silica fibres prepared by the authors, above 20 dB of gain with 2000 mW pump power at the 1050 nm pump band can be expected according to the simulations

The role of some glass network modifiers on the quantum efficiency of the near-infrared fluorescence from the 3 H 4 level of Tm 3+ ion in silica-based doped fibers is studied. Modifications of the core composition affect the spectroscopic properties of Tm 3+ ion. Adding 17.4 mol% of AlO 3/2 to the core glass caused an increase of the 3 H 4 level lifetime up to 50 ls, 3.6 times higher than in pure silica glass. The quantum efficiency was increased from 2% to approximately 8%. On the opposite, 8 mol% of PO 5/2 in the core glass made the lifetime decrease down to 9 ls. These changes of Tm 3+ optical properties are assigned to the change of the local phonon energy to which they are submitted by modifiers located in the vicinity of the doping sites. Some qualitative predictions of the maximum achievable quantum efficiency are possible using a simple microscopic model to calculate the non-radiative de-excitation rates.

We present preparation and spectroscopic characterization of thulium-doped fibers with enhanced 3 H 4 fluorescence lifetime obtained by codoping with alumina. With an alumina content of 10 mol%, a fluorescence lifetime of 58 ls is achieved. For the first time we study and optimize the thulium-doped fiber amplifier (TDFA) with a dual-wavelength (800 + 1400 nm) pumping scheme, where the pump at 800 nm propagates in the cladding and the pump at 1400 nm propagates in the core. In the study we use numerical simulations and experimentally obtained fiber characteristics. The results are compared with those obtained for numerical simulation of a TDFA pumped at a single wavelength in the 1050 nm band.