FLUORESCENT SUBSTANCE OPTICAL FIBER

PURPOSE:To improve excitation efficiency and conversion luminescence luminance by adding Yb and one of Er, Tm, Ho, and Pr to a core composed essentially of a halide of an alkali metal, alkaline earth metal, or rare earth metal. CONSTITUTION:An essential component of a material forming a core is a halide of an alkali metal, alkaline earth metal, or rare earth metal, and at least Yb and one of Er, Tm, Ho, and Pr are added among rare earth metals to this core. As said halide, fluoride is preferably used. An optical fiber using such a compsn. as a core can achieve long distance transmission low in transmission loss when it transmits IR rays of excitation light. Since the IR and visible light conversion part can be united with a usual optical fiber to one body and constituted continuously, a high conversion efficiency of IR.visible light conversion is obtained without impairing the intrinsic merits of an optical fiber, i.e. thinness, toughness, and lightness.