Evaluation of extrinsic scattering loss due to crystallization in fluoride optical fibers

Extrinsic scattering loss caused by crystallization in current fluoride optical fibers is evaluated in order to investigate the possibility of realizing long-length low-loss fibers. In the current fabrication process, which consists of melting, casting, and drawing, crystallization occurs mainly in the latter two heat processes. Crystal initiation and growth are simulated based on the thermal history during these processes. Scattering loss is calculated from the crystal distribution obtained. When the preform diameter is increased, scattering loss increases rapidly. A low scattering loss is essentially expected only for the fibers drawn from small diameter preforms, although drawing has a relatively large effect on crystallization