Optical fiber with varied flat chromatic dispersion

• Comparison of refractive index decreasing dopants favors fluorine over boron oxide. • We demonstrate specialty optical fibers with variable flat chromatic dispersion. • Dispersion values and regime is tunable by changing core radius. • Simple manufacturing compared to microstructural optical fibers. This paper investigates the design and properties of the conventional all-solid silica based flat dispersion specialty optical fiber. The design utilizes depressed-clad type of refractive index profile which allows for precise control of the optical fiber modal properties, particularly the chromatic dispersion. Specifically designing the dopants concentrations and depressed clad to core diameter ratio allows to obtain optical fibers with flat chromatic dispersion ranging from anomalous to normal dispersion regime. The regime and the values of chromatic dispersion in optical fibers is obtained through the change of the core diameter with the refractive index profile being the same in all optical fibers. The influence of the dopant choice on the mechanical and optical properties is shown using finite element method (FEM) studies. The study demonstrates that fluorine is a better candidate than boron for optical fiber designs that require precise chromatic dispersion characteristics. Six optical fibers were manufactured with the same refractive index profile differing with core radius. This allowed to obtain optical fibers that have chromatic dispersion in anomalous region (17.82 ps/(nm∙km) at 1.96 µm) for the fiber DCFDF1 and normal region (−115.14 ps/(nm∙km) at 1.57 µm) for the fiber DCFDF6.