Sumitomo Electric Industries, Limited

Nippon Telegraph and Telephone Corporation

Sumio Hoshino

Masumi Ito

Hiroo Kanamori

Toshio Danzuka

Shinji Ishikawa

Yuichi Ohga

Kazuhiro Yonezawa

Haruhiko Aikawa

Katsuzo Mukai

Masayuki Shigematsu

Ichiro Tsuchiya

Tadashi Enomoto

Wataru Kikuchi

Tatsuhiko Saito

Keisei Morita

Kiichiro Kawasaki

Takeshi Kyogoku

Hisasi Izumita

Ichiro Tuchiya

Kanta Yagi

Takehiko Kito

An embodiment of the invention relates to a BI-MMF with OH group concentrations controlled along a radial direction. In the BI-MMF, an OH group concentration distribution along the radial direction has a shape in which a concentration peak is located in a concentration control interval provided between an outer periphery of a core and a trench part, including an interface between the core and trench part.

Multimode optical fiber

The present invention relates to a GI-type multi-mode optical fiber in which the outer diameter of the core is 47.5 to 52.5 &#x3bc;m or 60 to 65 &#x3bc;m, or to a bend resistant multi-mode optical fiber provided with resistance against property fluctuation caused by the bending of the multi-mode optical fiber by providing a trench portion having a low refractive index at the outer periphery of the core. In the multi-mode optical fiber, both the maximum tensile stress and the maximum compressive stress in the optical axis direction remaining in the core are 50 MPa or less.

Multi-mode optical fiber

The present invention relates to a multimode optical fiber having a structure for stably reducing eccentricity relative to an insert hole of a connector ferrule to be mounted at an end thereof, wherein a fiber outer diameter of the multimode optical fiber along its longitudinal direction varies periodically in a range of &#xb1;0.5 &#x3bc;m with respect to a target fiber outer diameter.

The present invention relates to a multimode optical fiber having a stably manufacturable structure as a transmission medium suitable for wide-band multimode transmission. In the multimode optical fiber, a core has a refractive-index profile a shape of which is defined by the exponent &#x3b1; which varies along a radial direction from a center of the core and an average of radial variation of which is positive in a predetermined range in the radial direction.

Multimode optical fiber including a core and a cladding

The present invention relates to a GI-type multi-mode optical fiber in which the outer diameter 2a of a core is 47.5 to 52.5 &#x3bc;m or 60 to 65 &#x3bc;m. In the multi-mode optical fiber, stress in the optical axis direction remaining in an outermost peripheral portion of the cladding is tensile stress of 0 to 25 MPa, the outermost peripheral portion of the cladding being defined as a region having a diameter of 1.8b or more when the diameter of the cladding is 2b.

The present invention relates to a multi-mode optical fiber having a structure enabling stable production and broadening of communication bandwidth as compared with the conventional structures. The multi-mode optical fiber has a core with a diameterthat is doped with GeOand chlorine. The chlorine concentration profile in the core along the diametric direction of the multi-mode optical fiber has a shape such that the chlorine concentration at a second measurement position within a range at a distance of from 0.9 a to 1.0 a from the center of the core in the radial direction thereof is higher than the chlorine concentration at a first measurement position at a distance of a/2 from the center of the core in the radial direction thereof.

The present invention relates to a multi-mode optical fiber having a structure which can be produced with good stability with a communication bandwidth broader than that in the conventional structures, and in which both GeOand chlorine are added to a core thereof, and chlorine is also added to a cladding thereof. The cladding contains chlorine such that the average chlorine concentration therein becomes higher than the average chlorine concentration in the core.

A method of making a glass is provided in which the time needed for doping a refractive index control substance such as fluorine into a soot glass deposit body can be reduced. The method comprises the steps of: (1) putting a soot glass deposit body in a container; (2) doping a refractive index control substance into the soot glass deposit body by supplying an doping gas into the container, the doping gas containing the substance; and (3) consolidating the soot glass deposit body by heating, wherein the final set-value concentration of the substance is determined beforehand depending on the target refractive index of the glass, and in step (2), the container is supplied with the doping gas including the substance having a concentration set to be higher than the final set-value concentration, and subsequently, the doping gas including the substance having the final set-value concentration is supplied into the container.

Method of making glass

To provide a elongating method for elongating an optical fiber parent material with high reliability by implementing a high precision control for the outer diameter in short time. This elongating method includes a process for switching a control method for at least one of the control items of measurement object, based on at least one of a difference between measured value and target value and a change rate of the difference per unit time, in measuring the outer diameter of a glass parent material elongating portion and making a feedback control for the elongating conditions based on the difference from the target outer diameter.

Method for drawing glass parent material and drawing machine for use therein

An object of the present invention is to reduce the adhesion of floating glass particulates to the surface of a soot preform during the manufacture of the soot preform, thereby reducing the voids generated in the transparent glass preform made from the soot preform, and to improve the quality of the optical fiber manufactured from the transparent glass preform. The equipment of the invention is equipped with a reaction vessel , a burner provided within the reaction vessel into which raw material gas and combustion gas are supplied so as to generate glass particulates by hydrolysis reaction, and a starting rod onto which the glass particulates generated by the burner are deposited. By drawing up the starting rod while turning it around its axis, the glass particulates are deposited on the tip of or around the starting rod to form a soot preform in column-like shape. The equipment is provided with a partition board that separates part of the space around the soot preform in the reaction vessel into upper and lower parts. An exhaust port is provided below the partition board in the inner wall of the reaction vessel , and the burner is installed in the space below the partition board

Porous glass base material production device and method

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

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

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.

Growing community of inventors

Yokohama, Japan

Sumio Hoshino