Abstract: An optical fiber comprising core glass having therearound a cladding comprising fluorine-containing quartz glass and a process for producing the same are disclosed. Said cladding is composed of an inner portion having a prescribed thickness and a constant fluorine content through its thickness and an outer portion having its fluorine content being gradually decreased in a radial direction so that its outermost surface has a fluorine content of about 0.7% by weight or less relative to SiO.sub.2.

Abstract: A method for producing a glass preform comprising flame hydrolyzing a glass raw material in an oxyhydrogen flame to form glass fine particles of quartz, depositing the glass fine particles on a seed member to produce a solid or hollow cylindrical soot preform at least of a part of which contains GeO.sub.2, and heating and sintering the soot preform by introducing it in an atmosphere comprising an inert gas at least a part of which is kept at a temperature not lower than 1,600.degree. C. at an introducing rate not smaller than 3 mm/min, from the glass preform produced by which method, an optical fiber having longitudinally homogeneous composition and low attenuation of light transmission is fabricated.

Abstract: A method for producing a glass preform for an optical fiber by an outside vapor-phase deposition method, which comprises forming fine glass particles by jetting gaseous glass raw material and fuel gas from a first burner to deposit the particles on a seed rod to form a soot rod at such a temperature that a specific bulk density of the soot rod being formed is low and subsequently heating the soot rod by a second burner so as to increase the bulk density of the soot and then sintering the soot rod to obtain a transparent glass preform for an optical fiber, by which method, a highly pure glass preform is produced in a good deposition yield without cracking.

Abstract: A method for producing an optical fiber preform comprising injecting a glass raw material, a gaseous fluorine-containing material and oxygen gas from a first nozzle, inactive gas from a second nozzle which surrounds the first nozzle and hydrogen gas from a third nozzle which surrounds the second nozzle, flame hydrolyzing the glass raw material to synthesis fine glass particles and depositing the fine glass particles on a tip of a rotating seed rod to produce the optical fiber preform containing fluorine.

Abstract: A method for producing a glass preform for optical fibers by heating a glass soot preform consisting of glass fine particles made mainly of silicon oxide, which method comprises the steps of:(1) heating the glass soot preform to dehydrate and to remove impurities therefrom;(2) heating the glass soot preform in a gas atmosphere containing at least fluorine or fluorine-based compound to add fluorine to the glass soot preform; and(3) heating the glass soot preform to make it transparent, from the transparent preform prepared by which method, an optical fiber having superior transmission characteristics can be prepared.

Abstract: A high frequency induction coupled plasma torch is disclosed. The torch is comprised of a multi-pipe structure and is used for forming a plasma flame by high frequency power induction. The torch is comprised of a plurality of pipes which are coaxially arranged within each other. Each of the pipes has one or more flanged openings positioned on its surface whereby it is interconnected to the adjacent pipe. By means of the flanged openings any given pipe may be interconnected with any number of outer pipes. The torch can be economically produced and maintained.

Abstract: A process for producing high-purity silica glass wherein glass-forming chlorides, hydrogen gas, oxygen and an inert gas are supplied from a glass burner, the chlorides are decomposed by flame oxidation to form fine grains of glass which are deposited on a starting member and the glass deposit is sintered to provide a transparent vitreous substance, the volume ratio of oxygen gas to the sum of the chlorides and hydrogen gas being greater than about 0.6, preferably greater than about 1.0, and less than about 20.

Abstract: A process for producing a preform for glass fiber for optical transmission by heating supply gases to form fine particles that are deposited on a rotating starter member to form an aggregate of fine glass particles which are then sintered to give a transparent vitreous material, characterized by a first heating stage wherein the aggregate of fine glass particles is sintered by increasing the temperature at a constant rate in a gaseous atmosphere which contains a halogen or halide and which has dehydrating activity, followed by holding the aggregate for a given period of time at a temperature in the range that causes considerable shrinkage of the aggregate, and a second heating stage where said aggregate is heated to the vitrifying temperature.

Abstract: A process for producing an optical fiber preform which comprises forming a particulate glass rod in which the dopant concentration gradually increases toward the center of its cross section, and gradually heating the rod starting at a temperature below the minimum collapsing point of the fine glass particles in the center of the rod in such a manner that the softening of the rod proceeds from the center outward, to thereby produce a transparent glass rod.

Abstract: A method of manufacturing glass rod for optical waveguides is proposed. In this method, several gaseous mixtures or powdery mixtures of materials for glass forming are reacted at a high temperature and deposited on the top or end of a rotating glass rod which is initially deposited on a rotating base plate and grown in the form of a rod of a fixed powdery or vitreous state. It is possible to obtain the glass rod having a predetermined radial distribution of index of refraction.