Reduction of OH-absorption in fluoride glasses

The thermodynamics of hydrolysis reactions show that hydroxyle groups are not stable in glass melt at high temperature. A refining stage carded out at 1000°C for 1 h results in low-OH-content bulk glasses. Preforms were prepared by this method and drawn into fibers. The maximum absorption of 2.9 μm was 110 dB/km and a minimum transmission loss of 16 dB/km was observed at 2.6 μm.