Abstract: An optical waveguide is disclosed which exhibits only slight attenuation over both the visible and near infrared range. The waveguide comprises an optical fiber whose core is made up of a fluorine-doped silica glass possibly comprising an oxide that increases the index of refraction of said silica.

Abstract: A process is described for making a doped-silica ingot useful in the manufacture of optical fibers. At least a silicon compound and a titanium compound are decomposed in the flame of the induction plasma burner in the presence of a determined supply of hydrogen and are reacted with the oxygen contained in the burner feed gas and/or in the vector gas to form SiO.sub.2 and H.sub.2 O against a heat-stable support. As a result silica and titanium oxide are deposited on the support in the form of a homogeneous vitreous mass exhibiting a selected concentration of hydroxyl groups between 10 and 50 parts per million. Fluorine-doped silica is deposited radially in the same way on the resulting ingot. The resulting semifinished product is a cylinder consisting of a titanium-doped silica core, whose TiO.sub.2 concentration by weight is about 0.1 to 8%, covered by a sheath of fluorine-doped silica, whose fluorine concentration is about 0.1 to 3%.

Abstract: The present invention relates to a process for the continuous manufacture of vitreous synthetic silica doped with fluorine. This process consists of decomposing a silicon compound free of hydrogen in the flame of an inductive plasma burner, thereby forming silica upon reacting with the oxygen contained in the burner feed gas. A gaseous inorganic fluorine compound free of hydrogen, is sent into the flame preferably from outside the burner. Said fluorine compound simultaneously with the silicon compound decomposes whereby fluorine is introduced into the silica, lowering its index of refraction. The doped silica is then deposited on a heat-stable support in the form of a vitreous mass. The doped synthetic silica is particularly useful for making preforms for optical transmission fibers.