The authors report on the GeSx glass system as host glass material for Pr3+-doped fiber amplifiers in the 1.3 mm telecommunications window. GeS2 glass is easily devitrified by a dopant level of 50 ppm Pr but in GeS2.015 glass 200 ppm Pr is sol.; by adding a small amt. of S the host glass is stabilized. The 1G4-3H5 luminescence of 200 ppm Pr-doped GeS2.015 peaks at 1.34 mm. The photoluminescence decay of the Pr3+ 1G4 state in this glass is nonexponential but can be characterized as a 2-exponential decay, with ta = 175 +- 40 ms and tb = 830 +- 100 ms. For GeSx with x >= 2.05 the soly. of Pr is low. At a dopant level of 200 +- 50 ppm phase sepn. of a secondary submicron phase gives glass-ceramics.