Nonlinearity in Fluoride Glass Single-Mode Fibers for Optical Communication

The low projected attenuation loss of fluoride glass down to 0.02 dB/km in the wavelength region around 2.5 μm has motivated the development and characterization of fluoride fiber, in particular ZBLAN-based fiber, for use in long-range optical links. At this attenuation value, repeaterless systems up to approximately 500 km in length should be realizable while undersea or transcontinental links would still require a few repeaters for attenuation and/or dispersion compensation. Analogous to silica fibers, the fiber nonlinearity may be employed as a means of overcoming the dispersion limitation to the maximum achievable bitrate through soliton pulse propagation while stimulated Raman scattering is capable of supplying distributed gain over a broad frequency range in both linear and nonlinear systems. The soliton-based system places, however, comparatively stringent demands both on the soliton source and on the distance between repeaters to maintain the soliton energy and stability. After presenting the relevant physical properties of the fiber, this work therefore first questions the viability of soliton versus linear pulse transmission for communication purposes in fluoride fiber by comparing their single-channel information carrying capacities.