Fiber drawing ability and loss optimization of niobium rich borophosphate optical glass fibers

Abstract

Here we explore the manufacturing of niobium-rich borophosphate glasses into fibers with optical quality. Glass preforms of composition [(100-x) (0.95 NaPO3 + 0.05 Na2B4O7) - x Nb2O5] with x = 37, 38, 39, 40 were synthetized and thermally drawn. Viscosity measurements performed in the softening point range show that the optical fiber drawing temperature gradually increases with the amount of niobium oxide. X-ray diffraction and Raman structural analysis performed post drawing demonstrate that the BPN glass with 39% Nb2O5 represents the upper limit for fiber drawing under oxygen. Subsequently, preform quenching protocol was optimized to mitigate the density fluctuations within the glass matrix related to convection flows and compare with the conventional cast-in-mold method. Optical transmission and shadowscopy imaging highlight the improvement in the optical quality of the glasses produced following this new protocol. This observation is confirmed by cut back loss measurements which show a decreasing in the attenuation from 6.04 dB/m to 3.19 dB/m between the two methods. One believes the manufacturing of niobium rich borophosphate fibers with improved optical quality highlights their potential to be used as near-infrared highly nonlinear waveguide devices.