Recent Advances in Fluoride Glass Fiber Optics in the USA

Optical fibers based on heavy metal fluoride glasses are of interest because of their low intrinsic loss. Oxide-based fibers have a minimum attenuation of 0.15 dB/km at 1.55 mu m. This operational window is limited by Rayleigh scattering at short wavelengths and by multiphonon absorption at long wavelengths. In contrast, fluoride glasses have lower Rayleigh scattering as well as a multiphonon edge that is shifted to longer wavelengths. This permits fluorozirconate glasses to have a theoretical minimum attenuation of < 0.01 dB/km at 2.55 mu m. Possible applications for these fibers include ultra-low loss communication links, radiation resistant links, remoting of IR focal planes and IR power delivery. Most of the interest in this field has been sparked by the potential for ultra long (thousands of kilometers), repeaterless undersea communication systems. Such repeaterless links may decrease system cost and cable weight, while increasing overall reliability and ease of repair compared to conventional silica-based optical fibers. Other applications such as remoting of IR focal planes take advantage of the high IR transparency of these fluoride waveguides. 7 ref.--AA