Generally, Te based compositions are designed for optimal phase change materials for optical or electric storage of numerical data due to their strong tendency to crystallize.In another aspect, due to its unique transmission window up to 25 μm, telluride glasses have attracted much attention to the so-called Darwin mission by European Space Agency (ESA) whose objective is to discover extra solar earth-like planets and analyze their atmosphere in the spectroscopic band of 6~20 μm.However, the application in this area was rather limited by the poor thermal stability against devitrification during the process of sensing fiber drawing.In this work, bulk glass samples were designed in the Ge-Te-AgI quasi-ternary system and prepared.Some of their basic properties, such as thermal stability, IR transmission, density, optical band gap, etc.were measured or calculated.Results show that by adding AgI, thermal stability of the glasses was significantly enhanced while thehigh transparency in the far infrared region was maintained, making the system optimal for fiber drawing.Furthermore, after careful purification and distillation processes on the raw materials (Ge and Te) used, glass fiber based on the glass samplewith no crystallization peak at all, was successfully drawn.The attenuation test result gives a quite high minimum loss of 17 dB/m, which is caused by the scattering loss due to bubbles and defects formed during the preparation of the preform.By optimizing the heating process during preform preparation, bubbles were significantly eliminated.This helps dramatically decrease the minimum loss to only about 3 dB/m.With low attenuation and wide IR transmission window, the obtained single index fiber is a promising candidate for application in IR sensing.