Gain dynamics play a crucial role in the design of laser oscillators and amplifiers. In order to expand the understanding of gain dynamics into the spectral 2 μm region, this study presents the experimental characterization of transfer functions in thulium-doped fiber amplifiers associated with the 3F4 → 3H6 transition that governs emission in this spectral range. The transfer functions for both the signal and pump are thoroughly investigated, providing detailed information on their magnitude and phase. We find a damped high-pass and a low-pass filtering behaviour for the respective signal and pump transfer function of thulium-ions in silica glass.