The search for very low loss fiber-optic materials

Today's fiber-optic communications systems are fused-silica-based fibers for which signals require reamplification every 30 kilometers. Repeaterless long-haul (transcontinental and transoceanic) links can only be envisaged if a new fiber material with intrinsic power losses significantly lower than those of silica can be identified and developed. This article reviews the development of silica-based systems, details the physical mechanisms which produce signal attenuation in fiber materials in general, and identifies that class of materials from which ultralow loss glasses are most likely to be developed in the future.