Abstract: The invention concerns a reaction chamber comprising a first container (1), a second container (4) connected to a conduit (6), an outer tube (3) emerging into the container (1), an outer tube (8) emerging into the conduit. The container (1) is designed to receive a sleeve glass, and the container (4) a core glass for optical fiber. The method for using said chamber, after vacuum sealing in (3a) and (8a), and heating the chamber at a sufficient temperature for melting the glasses, the chamber being in the position represented with the tube (3) in vertical position, consists: in a 180° anti-clockwise rotation about an axis perpendicular to the figure. The sleeve glass flows into the tube (3) while the core glass remains confined in the container (4); cooling the tube (3), then returning to the original position; part of the sleeve glass, maintained in liquid form in the center of the tube (3), drops into the container (1); carrying out another 180°, rotation, but clockwise.

Abstract: Fluoroglasses, their preparation and intermediate products obtained. These glasses are characterized by containing as the forming element at least about 10% by moles of a metal fluoride or mixture of metal fluorides of the formula MF.sub.n, n being a number equal to 3 or 4, M representing a 5f transition metal when n=4 (fluoride MF.sub.4) and a 4f transition metal or yttrium when n=3 (fluoride MF.sub.3), it being understood that said glasses are free of hydrofluoric acid as the forming element.

Abstract: Halogen glass is treated, while heated above its fusion temperature, with carbon disulphide. The resulting halogen glass is essentially free of parasitic absorption bands in the infra-red spectrum. The treatment with carbon disulphide apparently lowers the hydroxyl ion content and the metal-oxygen bonds sufficiently to avoid the infra-red absorption bands.