Phosphate glasses for optical fibers: synthesis, characterization and mechanical properties

Phosphate glasses (P2O5 - Al2O3 - Li2O - B2O3 - BaO - La2O3) are studied in the present work for the fabrication of passive optical fiber for amplifier and laser applications. Innovative phosphate glasses with large stability toward crystallization (more than 200°C), low transition temperatures (477 °C) and low thermal expansion coefficient (10 x 10-6 °C-1) have been successfully produced. Thermo-mechanical and optical properties of the glasses are presented and discussed with respect to the glass composition. Specific care was used to the design and fabrication of two glasses with adequate thermo-mechanical properties to be suitable in the fiber drawing process. Due to the inner surface quality of the tubes manufactured by the rotational casting, the fiber presents very high quality interface between the core and the cladding. Mechanical characterization of the obtained fibers allowed to evaluate tensile strengths of the order of 200-500 MPa and a Weibull modulus of about 10.