Abstract: Glass material for infrared ray-transmitting optical fibers comprises a three-component material made of a 28 mol % to 38 mol % BaF.sub.2 -2 mol % to 7 mol % GdF.sub.3 -58 mol % to 69 mol % ZrF.sub.4 -based composition. The glass material is cast in a metal mold with a hollow section which is preheated to a temperature of at least 100.degree. C. but below the glass deformation temperature and annealing the melt in the metal mold to form a glass rod. The glass rod forming step includes heating the melt in the temperature range of between about 200.degree. C. and less than the glass deformation temperature and cooling the melt. The glass rod is removed from the metal mold and optically polished at the ends and sides and is then drawn into a fiber while applying tension to the tip of the glass rod while the glass rod is being heated. The glass rod is drawn into a glass fiber while maintaining the temperature at the end portion of the glass rod constant.

Abstract: Glass for optical fibers is made of material of a binary system containing a fluoride selected from BaF.sub.2, SrF.sub.2 CaF.sub.2 and PbF.sub.2 and another fluoride selected from AlF.sub.3 and ZrF.sub.4.