Ultralow loss glasses.

Today's fiber-optic communications systems use fused-silica based fibers for which signals require reamplification every 30km or so. Repeaterless long-haul transcontinental or transoceanic links can be envisaged only if a new base fiber material with intrinsic power losses significantly lower than those of silica can be found and developed. This paper details the physical mechanisms which produce signal attenuation in solids in general and sets out the manner in which low loss limits depend on such fundamental properties as valence, both length, polarizability and molecular weight. In this manner the classes of materials from which ultralow loss glasses are most likely to be developed in the future can be identified. A brief review of the experimental progress made in the preparation and refinement of such candidate materials as chalcogenides, halides, and certain multicomponent oxides is also presented and a theoretical assessment of their ultimate loss capabilities given.