Abstract The effects of Sn and Bi additions on the properties and structure in Ge 2Se 5Te 3 glass have been studied by X-ray diffractometry, differential thermal analysis (DTA), analysis of weight-loss in solution, infrared (IR) transmission spectra and far Fourier-transform infrared (far FTIR) spectra for the purpose of expanding the IR transparency region of the Ge-Se-Te system glass and to decrease the fibre's attenuation at 10.6 μm. The additional Sn atom, which has formed [SnSe 4] tetrahedra, another type of network former in the glass network, increased the glass transition and crystallization temperatures, T g and T c, respectively, anti-crystallisation stability, chemical durability and IR multiphonon edge. The optimum glass composition in this quaternary system has a quantitative ratio (mol) of Ge/Sn ≈ 2. The most outstanding advantages of the Ge-Se-Te-Bi glass system are its excellent chemical durability and broad IR transparency region (the multiphonon absorption edge has been extended to 17.6 μm, 1.2 μm longer compared with the Ge-Se-Te system glass). Meanwhile, other properties of this glass are still somewhat better than the original Ge-Se-Te glass. These two chalcogenide glasses are candidates for drawing fibres for far-infrared transmission, especially for CO 2 laser radiation (10.6 μm) delivery in various environments.