A fiber laser using a thulium-doped ZBLAN gain medium was used to generate laser radiation simultaneously at 1461, 1505 and 1874 nm, with > 5 mW output power at each of the wavelengths. The laser was used to quantify the near-infrared absorption of liquid water in acetone. Additionally, near-infrared spectra were recorded using a broad band source and were interpreted using parallel factor (PARAFAC) analysis to rationalize the concentration-dependent peak shifts.