Thulium-doped silica-based optical fibers for cladding-pumped fiber amplifiers

We present preparation and spectroscopic characterization of thulium-doped fibers with enhanced 3H4 fluorescence lifetime obtained by codoping with alumina. With an alumina content of 10mol%, a fluorescence lifetime of 58μs is achieved. For the first time we study and optimize the thulium-doped fiber amplifier (TDFA) with a dual-wavelength (800+1400nm) pumping scheme, where the pump at 800nm propagates in the cladding and the pump at 1400nm 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 1050nm band.