Chalcogenide glass multi-mode and single-mode fibers

Double-crucible, rod-in-tube and preform drawing techniques were applied for the preparation of different fiber structures based on arsenic sulfide. Because of the low crystallization tendency and the high mechanical and chemical stability, this glass is favoured for passive and active fiber applications. By modification the base glass with small amounts of germanium, gallium, surplus-sulfur and other elements, both optical properties (refractive index, absorption edge, attenuation, fluorescence) and thermal properties (glass transformation, crystallization stability, viscosity, thermal expansion) can be controlled in a wide range. Moreover, the solubility of rare earth elements is influenced by the co-dopants. The interplay of these parameters in the drawing process was studied and described by mathematical models which enable the defined preparation of fiber geometry and refractive index structure. Besides the basic glass properties, microscopic defects and inclusions in the material are important for the fiber properties. The origin of such imperfections and their role in the different drawing technologies were demonstrated. Possibilities and limitations of the fiber preparation with special regard of active fibers are discussed.