Broadband submicron flattened dispersion compensating fiber with asymmetrical fluoride doped core

The goal of this paper is to investigate selected fluoride optical materials and to present a photonic crystal fiber designed for specific applications in dispersion compensation by using those materials. The idea how to restrict chromatic dispersion is to increase the index contrast by using calcium fluoride or barium fluoride in the first ring of holes, which lower the effective index. In general, fluoride materials compared to standard silica glass in many aspects offer better mechanical and optical properties. The use of fluorides allows achieving broadband dispersion suppression impossible to achieve in standard fibers with similar geometry. The presented result comprises a numerical model of a photonic crystal fiber in a submicron lattice, specific for its negative dispersion coefficient achieved for broad spectrum of telecommunication wavelengths, i.e. 1300 – 1700 nm. The core consists of pure silica surrounded by three doped regions and three air-holes. Holes doped with fluoride materials enhance negative dispersion coefficient to -438 ps.nm -1 .km -1 . The diameter of doped regions is about 1 micrometer. Simulations were done by using the full-vector FDFD method. The wavelength evolution of refractive index of materials was introduced by using the Sellmeier approximation. The major advantage of the designed fibers is their material composition, low attenuation and broadband utilization.