Reduction of scattering loss in fluoroindate glass fibers

The current fluoroindate glass optical fiber loss is dominated by extrinsic absorption and scattering loss. Attempts were made to reduce fluoroindate glass fiber loss by optimizing glass melting conditions, preform extrusion process and fiber drawing conditions. Our results show that fluorination of the glass batches (with 99.99% InF3) at 450 °C by addition of ammonium bifluoride reduced un-dissolved particles (potential scattering losses) in the glass. Glass flow analysis was carried out to provide insights into the glass temperature-viscosity behavior and the relationship between preform surface roughness and extrusion temperature, which enabled fabrication of preforms with low surface roughnesses and eventually reduced the fiber scattering loss. Fiber surface crystallization was reduced via conducting chemical etching and polishing (with colloidal silica) on both glass billets and preforms, extending the heating zone for fiber drawing, and applying additional weight at the bottom of preforms. As a consequence, the fiber surface roughness decreased, resulting in decreased fiber scattering loss and enhanced fiber strength.