Rare-earth (RE) doped optical fibers based on silica glass are frequently used as active gain medium in optical fiber lasers or amplifiers. Amongst other RE ions, trivalent ions of erbium, Er3+, and thulium, Tm3+, are especially attractive thanks to emission in near-infrared region around 1.5 and 2 μm, respectively. The fluorescence lifetime of the NIR emission is an important parameter for the evaluation of spectroscopic quality of RE-doped optical fibers and their suitability for laser operation. Moreover, the fluorescence lifetime plays an important role in various theoretical tasks, such as simulations of laser operation or calculation of energy transfer coefficients. The precise knowledge of fluorescence lifetime is therefore essential for the efficient design of lasers based on rare-earth-doped fibers. In this contribution, a large set of thulium- and erbium-doped fibers was prepared and analysed, and the influence of material of composition and fabrication processing on fluorescence lifetime was evaluated