The lifetime of 1.3 mu m emission from Dy3+-doped Ge-As-S glass containing very small amount of Ga and CsBr reveals interesting temperature dependence; with the addition of Ga/CsBr up to similar to 0.2 mol% the life-time decreases with increasing temperature. When the concentration of Ga/CsBr reaches similar to 0.3 mol%, however, the lifetime remains relatively constant regardless of temperature change. For further addition up to similar to 0.5 mol%, the lifetime increases as temperature rises. This uncommon behavior is explained through our understanding of the different temperature dependences of multiphonon relaxation and spontaneous emission rates associated with the thermally coupled Dy3+: (H-6(9/2), F-6(11/2)) manifolds in our modified chalcogenide glass. (C) 2012 Elsevier B.V. All rights reserved.