Infrared optical fibers

A state of the art review of nonsilica based infrared fibers is presented. Two types of fiber materials have been investigated- crystals and glasses. Crystal fiber work appears to be focused on development of short haul CO2laser power delivering lines at 10.6 μm. The maximum delivering power of the CW CO2laser has reached up to about 100 W by the polycrystalline KRS-5 fiber. A number of glass fibers are being developed in fluorides, sulfides, and heavy metal oxides. The best optical attenuation of each glass fiber has been respectively reduced to 21 dB/km at 2.55 μm for ZrF4-based glass fiber with a core-clad structure, 78 dB/km at 2.4 μm for As-S unclad glass fiber, and 13 dB/km at 2.05 μm (70 dB/km at 2.40 μm) for GeO2-Sb2O3glass fiber with a core-clad structure. Recent progress of these infrared fibers offers great potential for new wavelength fiber links operating in the m region which have not been realized by silica-based fiber.