Sulfide glass fibers for infrared transmission

Germanium sulfide glasses were drawn into fibers with optical losses lower than 1 dB/m. The glass fibers were coated with Teflon FEP or silicone resin according to their thermal properties. Loss increase caused by coating was not observed. The main problems in obtaining low-loss fibers were investigated. Sulphur evolution in fiber drawing was avoided by choosing the appropriate glass compositions and drawing conditions, OH and SH impurities were reduced to $\text{1}\text{4}$ of initial values using the S₂Cl₂ chemical reaction with water at 400–600°C. The possibility of ultra-low loss fibers using sulfide glasses is discussed in terms of intrinsic losses and impurity-related absorption losses.