Abstract: A surface of an optical fiber is coated by a method for coating a surface of an optical fiber with carbon comprising steps of introducing an optical fiber in a reaction chamber in the same direction as the flow of a coating raw material comprising carbon, hydrogen and halogen atoms and depositing on the surface of the optical fiber a carbon layer formed from the raw material by chemical vapor deposition, whereby the coated optical fiber has improved initial tensile strength and absorbs less hydrogen.

Abstract: A hermetically coated optical fiber comprising a core made of glass, a cladding made of quartz glass surrounding the core the outermost layer of which glass contains fluorine, and a carbon layer surrounding the fluorine-containing glass layer, which optical fiber has good initial strength and fatigue characteristics.

Abstract: A superconducting ceramic wire is produced by melting a superconducting ceramic-forming metal oxide composition, and quenching the melt into a glass which is then formed into a preform of thin plate. The preform is soften and wire-drawn without causing crystallization in a furnace into a flexible elongated thin tape having a thickness of e.g. 40 to 60 .mu.m. The tape is heat-treated for crystallization to obtain the superconducting wire. The disclosure mentions mainly Bi Bi-Sr-Ca-Cu-O superconducting systems.

Abstract: A hermetically coated optical fiber comprising a core made of glass, a cladding made of quartz glass surrounding the core the outermost layer of which glass contains fluorine, and a carbon layer surrounding the fluorine-containing glass layer, which optical fiber has good initial strength and fatigue characteristics.

Abstract: An optical fiberglass preform having fluorine selectively added to its cladding is produced by:depositing soot of quartz glass on a pipe from starting member by using burners for synthesizing glass soot to form a porous glass preform consisting of a core porous glass body a peripheral portion of which has a larger bulk density than the other portion and a cladding porous glass body,heating said porous glass preform in a dehydration atmosphere while supplying dehydration gas through the pipe form starting member andheating and vitrifying the dehydrated porous glass preform in an atmosphere containing a fluorine-containing compound.

Abstract: A surface of an optical fiber is coated by a method for coating a surface of an optical fiber with carbon comprising steps of introducing an optical fiber in a reaction chamber containing a coating raw material comprising carbon, hydrogen and halogen atoms and depositing on the surface of the optical fiber a carbon layer formed from the raw material by chemical vapor deposition, whereby the coated optical fiber has improved initial tensile strength and absorbs less hydrogen.

Abstract: A process for fusion-splicing hermetically coated optical fibers each of which comprises an inorganic coating, an optical fiber glass and optionally an organic coating, which process comprises removing the inorganic coating, fusion-splicing the fibers and then coating a portion where the inorganic coating is removed with an inorganic material.

Abstract: A superconducting ceramic wire is prepared from a superconducting ceramic-forming oxide composition by melting, the composition and quenching the melt to form a dense glass, which is soften and wire-drawn in a furnace. The resulting wire is heat-treated to form crystals and made into a superconducting ceramic wire. The wire has a flexibility and remarkable superconductivity which can further be improved by applying pressure to be made more dense and repeating the heat-treatment.

Abstract: A method of heating a quartz glass tube with microwaves, which method comprises supplying a gas for plasma generation in the quartz glass tube, applying microwaves to the quartz glass tube so as to generate a hot plasma in the quartz glass tube and to preheat the quartz glass tube, and then discontinuing the supply of the gas for plasma generation while applying the microwaves, whereby the quartz glass tube absorbs the microwaves to heat the quartz glass tube to a sufficient temperature in a very quick and clear manner.

Abstract: A method for producing a glass preform for an optical fiber comprising a core and a cladding containing fluorine is fisclosed. The method comprises forming a porous glass layer of substantially pure quartz on an outer surface of a fused glass rod consisting of a central portion of substantially pure quartz and a peripheral portion of quartz glass containing fluorine, and heating a composite of the fused glass rod and the porous glass layer in an atmosphere containing fluorine to add fluorine to the porous glass layer and to make it transparent, by which contamination of glass with hydroxyl groups can be prevented and light transmission characteristics of an optical fiber fabricated from the glass preform are improved.

Abstract: A method for producing a glass preform for use in the fabrication of an optical fiber which comprises inserting a core rod made of quartz glass in a cladding tube made of quartz glass added with fluorine, heating them from the outside of the cladding tube to fuse them together to form a primary glass preform comprising a core rod and a first cladding layer around the core rod, depositing SiO.sub.2 soot particles around the primary glass preform and thermally treating the soot deposited glass preform in the presence of a fluorine-containing compound to form a final glass preform from which an optical fiber is fabricated. From the glass preform produced by this method, an optical fiber having low attenuation of light transmission in a wide range of wave-length is fabricated.

Abstract: A glass preform for use in the fabrication of a dispersion shifted single mode optical fiber is produced by a method for comprising steps of inserting a core member consisting of an inner core part made of a germanium-added quartz glass which optionally contains fluorine and an outer core part made of a quartz glass having a refractive index smaller than that of the inner core part in a glass tube made of a fluorine-added quartz glass having a refractive index smaller than that of the outer core part, heating the core member and the glass tube to collapse the glass tube and fuse them together to produce a glass perform. The glass preform comprises a core member consisting of an inner core part made of GeO.sub.2 -SiO.sub.2 glass or GeO.sub.2 -F-SiO.sub.2 glass and an outer core part made of F-SiO.sub.2 glass and a cladding made of F-SiO.sub.2 glass and provides a dispersion shifted single mode optical fiber having reduced attenuation of light transmission in the 1.5 .mu.m wavelength band.

Abstract: A method for producing a glass preform for optical fibers in which fluorine is efficiently incorporated into the preform without incorporation of Fe or Cu. A fine glass particle mass, made primarily of quartz, is converted into transparent glass by heating it in a gas atmosphere containing at least a fluorine-based compound gas and a chlorine-based compound gas. The preferred heating range is 1,100.degree. to 1,400.degree. C.

Abstract: A rod-in-tube method for producing a glass preform for use in the fabrication of an optical fiber, which comprises steps of inserting a glass rod constituting a core material in a glass tube constituting a cladding material, heating the rod-tube composite by an outer heating source with introducing, in the gap between the rod and the tube, a gaseous mixture containing a silicon halogenide, a fluorine-containing compound and oxygen gas in which a ratio of silicon and fluorine (Si/F) is larger than 1/300 and smaller than 1/5, and heating and fusing the composite at a temperature not lower than 1,900.degree. C. with filling the gap by a gaseous mixture comprising a halogen-containing compound and oxygen gas; from which glass preform, an optical fiber with low attenuation of light transmission, particularly in a long wavelength range, is fabricated.

Abstract: A method for producing a glass preform for use in fabrication of an optical fiber, which comprises steps of forming a cylindrical rod of glass having a refractive index distribution with axial symmetry around the rod axis by an VAD method, stretching the rod glass to decrease its diameter, inserting the stretched rod in a glass tube having a refractive index distribution with axial symmetry around the tube axis and heating and melting a complex of the stretched rod and the tube to integrate them from the glass preform produced by the method, an optical fiber having precisely controlled refractive index distribution can be fabricated.

Abstract: A glass preform for an optical fiber having homogeneous distribution of bulk density in its radial direction is produced by a method comprising forming fine glass particles by jetting a gaseous glass material and a fuel gas from a burner, depositing the fine glass particles on a seed rod to form a soot rod with measuring a temperature of a part of the soot rod on which the glass particles are being deposited so as to control said temperature, and then sintering the soot rod to obtain a transparent glass preform.

Abstract: An optical fiber comprising a core essentially made of quartz and a cladding made of fluorine added quartz is fabricated with good productivity from a glass preform produced by a method comprising maintaining a hollow cylindrical porous glass preform in a first high temperature atmosphere comprising at least one fluorine-containing compound with jetting a cooling gas through the central hollow part of the porous glass preform to grade the amount of fluorine to be added in the radial direction of the porous glass preform and then sintering the porous glass preform in a second high temperature atmosphere kept at a temperature higher than the first high temperature atmosphere to make it transparent.

Abstract: A method for producing a glass preform for a single mode optical fiber comprising a core and a cladding, which method comprises depositing fine glass particle of a glass raw material on a periphery of a cylindrical seed member having a smooth and clean outer surface by flame hydrolysis to form a soot of the fine glass material, pulling out the seed member from the soot, inserting a core glass rod in a hollow portion of the soot and dehydrating and sintering a complex of a core rod and a cladding to produce a glass preform from which a single mode optical fiber having low attenuation of light transmission, particularly due to absorption by hydroxyl groups can be drawn.

Abstract: A rod-in-tube method for producing a glass preform for use in the fabrication of an optical fiber, which comprises steps of inserting a glass rod as a core material in a glass tube as a cladding material, fusing and closing one end of the cladding material, filling a gap between the core and cladding materials with an atmosphere containing at least one gaseous halogen-containing compound and then heating the core and cladding materials at a temperature not lower than 1,900.degree. C. to collapse the gap between them and to fuse them together, from which glass preform, an optical fiber with low attenuation of light transmission is fabricated.

Abstract: A method of producing a highly pure glass tube having a smooth inner surface, said method comprising the steps ofdepositing by the flame hydrolysis of a glass-forming raw material, a first layer of glass soot particles having a bulk density no greater than 0.2 g/cm.sup.3 on a seed member having a smooth and clean outer surface,depositing on the surface of the first layer of glass soot particles, a second layer of glass soot particles having a bulk density greater than that of the first layer by at least 0.03 g/cm.sup.3,drawing the seed member from the deposited two-layered glass soot preform to form a tube of glass soot particles,removing the first inner layer of glass soot particles from the second layer, either simultaneously with or subsequent to the drawing of the seed member from the soot preform, andheating and vitrifying the tubular glass soot preform to form a transparent solid glass tube.