Reduction of Impurities in Fluoride Glass Optical Fiber

A sublimation purification technique was developed for fluoride fiber materials, ZrF4, BaF2, GdF3, and AlF3. Using these purified materials and a “build-in casting” method, the low-transmission-loss of 8.5 dB/km at 2.12 µm was o btained, which is the lowest loss in an infrared ray transmitting fluoride glass fiber. The impurity level of the fiber was estimated as below 0.5 ppm by loss-factor analysis.