Fabrication of extruded fluoroindate optical fibers

Abstract

Fluoroindate glasses are attractive materials for the fabrication of mid-infrared transmitting fibers with extended spectral range. Preparation of fluoroindate glasses under different melting conditions and preform fabrication using the billet extrusion technique were investigated in this study. Experimental results showed that the fluorination of the raw materials using ammonium bifluoride reduced OH content and oxide impurities, and enhanced the crystallization stability of the glasses. In addition, a shift of the IR absorption edge to longer wavelength was observed by using ammonium bifluoride. Casting and extrusion methods were compared for application to preform fabrication. In this work, the fiber with the lowest loss (~2 dB/m at 1.55 μm) was obtained using preform extrusion at 322 °C. The significantly reduced loss of the fiber made from the extruded preform compared to the fiber made using a cast preform is attributed to the suppression of scattering centers and the better surface quality of extruded rods compared with the cast rod.