Sumitomo Electric Industries, Limited

Mitsubishi Chemical Corporation

Nippon Telegraph and Telephone Corporation

Mitsubishi Kasei Corporation

Other

Masumi Ito

Sumio Hoshino

Toshio Danzuka

Hiroo Kanamori

Shinji Ishikawa

Masayoshi Murayama

Kenji Shima

Yuichi Ohga

Ichiro Tsuchiya

Masakatsu Hatano

Hiroshi Yokota

Akira Inoue

Haruhiko Aikawa

Masakazu Shigehara

Masahiro Takagi

Tatsuhiko Saito

Yasushi Tsurita

Maki Inai

Eisuke Sasaoka

Masayuki Nishimura

Tatsuya Konishi

Masayuki Shigematsu

Toshifumi Hosoya

Masatoshi Hayakawa

Kazuyuki Sohma

Tadashi Enomoto

Seiko Mitachi

Toru Iwashima

Tatsuhiko Saitoh

Yoshiaki Miyajima

Kazuhiro Kuwa

Shin-ichi Furukawa

Maki Ikeji

Katsuzo Mukai

Ken Shiraga

Takeshi Kyogoku

Hisasi Izumita

Ichiro Tuchiya

Takehiko Kito

Provided is a glass fine particle deposit in which a pH of glass fine particles on a surface of the glass fine particle deposit is 5.5 or more and less than 8.5, in which a color difference ΔE*ab with respect to a white calibration plate when the surface of the glass fine particle deposit is measured by the SCI method using a spectrophotometer is 0.5 or more and less than 5. Provided is a method for manufacturing a glass preform including: manufacturing a transparent glass preform by heating a glass fine particle deposit in which a pH of glass fine particles on a surface of the glass fine particle deposit is 5.5 or more and less than 8.5; and measuring the surface of the deposit by the SCI method using a spectrophotometer and determining whether a color difference ΔE*ab with respect to a white calibration plate is 5 or more.

Glass fine particle deposit and method for manufacturing glass preform

An optical fiber sheetincludes an optical fiberand a wirethat are arranged between a first sheet and a second sheet. The optical fiberis a multi-mode optical fiber having a core of silica glass to which a refractive index adjuster is added, has a numerical aperture equal to or less than 0.30 and a flexural rigidity equal to or less than 0.50 N&#xb7;mm, and is bent to be arranged between the first sheet and the second sheet. The wireintersects the optical fiberbetween the first sheet and the second sheet.

Optical fiber sheet

For an index change of an interfacial region which is formed in a boundary between core region and cladding region and which decreases its refractive indices from the core region side to the cladding region side, a change rate in relative index difference (0.5&times;&Dgr;n)/(d/r) normalized by a core radius r, obtained for a domain of change from 0.8&times;&Dgr;n to 0.3&times;&Dgr;n relative to a relative index difference &Dgr;n of the core region , is used as an index for evaluation of refractive index change and an allowable range of values thereof is set to a range of the lower limit of 0.4% to the upper limit of 4.0%, whereby a single-mode optical fiber capable of low loss phototransmission can be realized while reducing influence of a tail spread and strain in the optical fiber.

Single-mode optical fibers and fabrication methods thereof

In a soot-deposition container, raw material gas and at the tip of a starting glass rod, combustion gas, and carrier gas are supplied to a core-depositing burner and raw material gas, combustion gas, carrier gas, and gas for doping of fluorine are supplied to a cladding-depositing burner, thereby forming porous glass soot comprised of glass soot for core and glass soot for cladding. With growth of soot, the supply amount of the fluorine-doping gas is increased while supply amounts of the other gases are kept constant. Next, dehydration process and transparentizing process of soot are carried out to obtain a glass preform for optical fiber. Fabricated in this way is the glass preform for optical fiber having the silica glass portion doped with low-concentration fluorine with high uniformity in the growth direction.

Increasing a fluorine compound flow rate during a VAD process

The present invention relates to an optical fiber grating as an optical component comprising an optical fiber having a core and a cladding, and a grating photowritten in the optical fiber. In particular, in the optical fiber grating in accordance with the present invention, the optical fiber into which the grating periodically changing the refractive index in the waveguide along the advancing direction of light is photowritten has a depressed cladding type refractive index profile. Accordingly, when the configuration of the optical fiber having a depressed cladding type refractive index, employed as the object in which the grating is photowritten, is changed, the stability in characteristics as the optical component or the like can easily be improved.

Low transmission loss optical fiber having a grating

This invention relates to an optical fiber grating and a method of manufacturing the same. According to the method, a hydrogen doping process is performed before ultraviolet irradiation in order to obtain a sufficient photoinduced refractive index change. In particular, a target for the hydrogen doping process of the method is characterized by a coated fiber obtained by covering the outer surface of the bared fiber having a core region and a cladding region with the resin. After the coated fiber is exposed in a hydrogen atmosphere in a predetermined pressurized state for a predetermined period of time, the resin is partially removed. An ultraviolet ray is irradiated on the predetermined area of the bared fiber from which the resin is removed, thereby forming a reflection grating in the core region. The method is also characterized in that the pressure of the hydrogen atmosphere is reduced from the pressurized state while adjusting the pressure reducing rate. Degradation of the bared fiber surface can be prevented, and generation of bubbles or the like between the bared fiber and the resin coating can also be prevented, thereby obtaining an optical fiber grating with high reliability.

Optical fiber grating and method of manufacturing the same

The optical connector according to the present invention comprises, at least, an optical filter with a waveguide structure having a grating with a predetermined reflection wavelength and a plug attached to a tip of the optical filter. The grating is disposed at a tip portion of the optical filter and accommodated in the plug attached to the tip portion of the optical filter. Further, the optical connector has various light-blocking structures for preventing unnecessary light from traveling a filter region of the optical filter including the grating.

Optical connector

A glass preform for an optical fiber is effectively drawn by connecting dummy rods to both ends of the glass preform and connecting the dummy rods to fitting members.

Method for drawing glass preform for optical fiber

This invention provides an optical waveguide having diffraction gratings with sufficiently high reflectivity, a waveguide member for obtaining the optical waveguide, and a production process thereof. An optical waveguide in which desired diffraction gratings are formed in a core and in a cladding at a predetermined portion by using a waveguide member in which germanium dioxide is added in the core and in the cladding and irradiating the predetermined portion of the waveguide member with interference fringes of ultraviolet light. By this, the optical waveguide according to the present invention reflects guided light throughout the entire mode field region, thus having a high reflectivity.

Optical waveguide and process for producing it

The present invention relates to a method for precisely elongating a glass preform of an optical fiber body having a desired outer diameter. In this method, a predetermined part of the glass preform is elongated as tensile stress is applied to one end of the glass preform while a predetermined part of the glass preform is heated and softened successively from one end toward the other end of the glass preform. In this elongating operation, while the outer diameter of the softening portion of the glass preform is measured, the tensile stress is adjusted such that the outer diameter of the softening portion coincides with a preset value of the control outer diameter. In particular, this method is characterized in that the preset value of the control outer diameter is changed at least during a predetermined period until termination of elongation or during a predetermined period from the start of elongation.

Method for elongating glass preform

In order to provide an improved process for the production of a glass preform for an optical fiber which includes substantially no bubble formation therein and also has a substantially uniform shape, the present invention provides a process for the production of a glass preform which is at least partially formed from silica. In particular, a body is formed on a rod by depositing fine glass particles thereon, preferably by the vapor phase reactions, and heating the body to vitrify under a reduced atmosphere or a vacuumed atmosphere so that the glass preform is produced. According to this process, the heating includes a first heating step of degassing the body at a first heating temperature, a second heating step of shrinking the body at a second heating temperature which is higher than the first heating temperature and which is lower than a third heating temperature, and a third heating step of vitrifying the shrunken body at the third temperature which corresponds to a vitrification temperature of the fine glass particles so as to produce the glass preform.

Process for production of glass preform for optical fiber including

A method of manufacturing an optical fiber in which the deviation of a cutoff wavelength from a design value can be minimized. It is found that, upon diameter reduction of a porous core glass body by heat treatment, when the diameter reduction ratio is set to a value larger than 0.90, a 'spike' in the refractive index distribution curve of a core can be prevented, and the deviation of the cutoff wavelength from the design value can be minimized. Therefore, there is provided a method comprising the first step of depositing fine SiO.sub.2 particles and fine GeO.sub.2 particles, which are produced by a core formation burner, to grow a porous core glass body from a distal end of a rotating starting rod in an axial direction, the second step of performing diameter reduction by heating the grown porous core glass body by heating means while growing the porous core glass body, and the third step of depositing fine SiO.sub.2 particles produced by a cladding formation burner to form a porous cladding glass layer on an outer surface of the diameter-reduced porous core glass body while performing growing and diameter reduction of the porous core glass body, wherein an outer diameter of the porous core glass body after the third step of depositing is larger than 0.90 times an outer diameter before diameter reduction.

Method of manufacturing single-mode optical fiber

A process for producing a vanadium-phosphorus oxide-containing catalyst precursor, which comprises (a) introducing into an organic solvent a vanadium alkoxide as a pentavalent vanadium compound and a phosphorus compound in the presence of a reducing agent capable of reducing the pentavalent vanadium compound to a tetravalent state, (b) hydrolyzing at least a part of the vanadium alkoxide before or after the introduction of the phosphorus compound, and (c) heating the vanadium-containing liquid medium obtained in step (b), in the presence of the phosphorus compound to reduce at least a part of vanadium to a tetravalent state.

Process for producing a vanadium-phosphorus oxide catalyst precursor

A process for producing a precursor of a phosphorus-vanadium oxide catalyst for production of maleic anhydride by vapor phase oxidation of a hydrocarbon having 4 carbon atoms, which comprises reacting phosphoric acid and a pentavalent vanadium compound in an organic solvent capable of reducing at least a portion of the pentavalent vanadium to a valence state of +4, the phosphoric acid being substantially composed of orthophosphoric acid, and a phosphoric acid solution whose concentration is 88 to 96% being used as a source of the phosphoric acid; and a process for producing the catalyst comprising dry-pulverizing the catalyst precursor.

Process for producing a phosphorus-vanadium oxide catalyst precursor,

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Yokohama, Japan

Masumi Ito