By conventional melt-quenching techniques, a series of Dy3+-doped (0.1 to 1.0 wt%) Ga5Ge20Sb15S60 bulk glasses were fabricated and their potential for developing mid-infrared fiber laser beyond 4 mu m were evaluated, in which the optimal Dy3+ doping concentration was found to be 0.3 wt% and the largest laser quality factor value (sigma(e) x tau(mea) = 2.62 x 10(-23) cm(2) s) among all of the Dy3+-doped chalcogenide glass was obtained. On this basis, through using the chemical purification methods with chlorine gas combined with the dynamic distillation process, the high-purity GGSS glasses with low O-H and S-H absorptions were successfully fabricated, which was confirmed by the optimized mid-infrared linear transmittance and improved fluorescent lifetimes of Dy3+: H-6(13/2), H-6(11/2) levels. Furthermore, for the first time to the best of our knowledge, the Dy3+-doped, single-mode, and double-cladding chalcogenide fibers with the core/cladding ratios of 125:60:11 and 125:66:11.5 were achieved by a multistage rod-in-tube fiber drawing process and extrusion methods, respectively. The GeS2-based fiber exhibits excellent transmission performance at 1.0-5.0 mu m: 3.0 dB/m at 2.9 mu m (O-H), 2.4 dB/m at 4.1 mu m (S-H). Combining the advantages of high-purity, high doping concentration and single-mode double-cladding structure, the optimized active fiber should be an ideal efficient and low-threshold medium toward mid-infrared fiber laser beyond 4 mu m.