Sumitomo Electric Industries, Limited

Kyushu University

Tetsuya Haruna

Masaaki Hirano

Yoshiaki Tamura

Tetsuya Nakanishi

Shinji Ishikawa

Atsushi Inoue

Motoki Kakui

Masashi Onishi

Yuki Kawaguchi

Takahiro Murata

Kazumasa Makihara

Tetsuya Hayashi

Yoshinori Yamamoto

Tomoyuki Hattori

Ichiro Tsuchiya

Wataru Sakurai

Satoshi Tanaka

Mitsuaki Tamura

Toshiki Taru

Hirotaka Sakuma

Yoshihiro Saito

Iwao Okazaki

Kazumasa Oishi

Kazunori Tanaka

Manabu Ishikawa

Maki Ikeji

Nobuyuki Taira

Junji Iihara

Motohide Yoshida

Kazuyuki Soma

Tetsutarou Katayama

Nobuhiro Hikichi

Maki Ikechi

Yoshihiro Tukuda

Kazuto Saito

A method for manufacturing an optical fiber preform including a core part and a cladding part is disclosed. The method includes: adding an alkali metal to an inner surface of a silica-based glass pipe; etching the inner surface of the silica-based glass pipe to which the alkali metal is added; making a glass rod by collapsing the silica-based glass pipe after the etching; and making an optical fiber preform using the glass rod. The silica-based glass pipe is heated in the adding such that a surface temperature of the silica-based glass pipe falls within a temperature range of 1500&#xb0; C. or higher to lower than 2000&#xb0; C.

Method for manufacturing optical fiber parent material, and method for manufacturing optical fiber

The present invention relates to a method of manufacturing an optical fiber preform for obtaining an optical fiber with low transmission loss. A core preform included in the optical fiber preform comprises three or more core portions, which are each produced by a rod-in-collapse method, and in which both their alkali metal element concentration and chlorine concentration are independently controlled. In two or more manufacturing steps of the manufacturing steps for each of the three or more core portions, an alkali metal element is added. As a result, the mean alkali metal element concentration in the whole core preform is controlled to 7 atomic ppm or more and 70 atomic ppm or less.

Method of manufacturing optical fiber preform and optical fiber preform

An optical fiber preform of the present embodiment comprises a core portion and a cladding each comprised of silica glass. The core portion has a first dopant region including a central axis of the core portion and a second dopant region away from the central axis. The first dopant region contains a first dopant selected from among Na, K, and their compounds, and a concentration of the first dopant is 10 atomic ppm or more but 2,000 atomic ppm or less. The second dopant region contains a second dopant reducing viscosity of the silica glass. The second dopant has, as a characteristic at a temperature of 2,000&#xb0; C. to 2,300&#xb0; C., a diffusion coefficient of 1&#xd7;10cm/s or higher but lower than that of the first dopant, and a concentration of the second dopant region is 10 atomic ppm or more.

Optical fiber preform

The present embodiment relates to an MCF having a low transmission loss and having a structure for reducing a transmission loss and effectively suppressing an inter-core XT. The uncoupled MCF includes alkali metal having a predetermined concentration in which each of a plurality of cores contributes to reduction in the transmission loss, and a core pitch is set so that a sum h_total of power coupling coefficients of a specific core and the remaining all cores of the plurality of cores is 2.3&#xd7;10/km or less.

Multicore optical fiber

There is provided a method for producing a low-loss alkali metal-doped silica core optical fiber having excellent hydrogen resistance. The method for producing the optical fiber according to the present invention includes a drawing step of drawing an optical fiber preform in a drawing furnace to produce a silica glass-based optical fiber including a core region containing an alkali metal with an average concentration of 0.5 atomic ppm or more and a cladding region that surrounds the core region and a heating step of heating the optical fiber in a heating furnace through which the optical fiber drawn from the drawing furnace passes.

Method of making an optical fiber containing an alkali metal in the core

One of embodiments relates to an optical fiber in which an alkali metal element is efficiently doped to its core to suppress transmission loss from increasing. A mean concentration or a concentration distribution of the alkali metal element is adjusted such that 0.48 or less is obtained as an weighted value obtained by weighting a distribution of field intensity of guided light at a wavelength of 1550 nm, with respect to a radial direction distribution of a ratio I/Iof an intensity Iof Raman scattering light by a silica three-membered ring structure and an intensity Iof Raman scattering light by a Si&#x2014;O stretching vibration, in a cross-sectional region having a diameter of 20 &#x3bc;m.

Optical fiber

An optical fiber having a reduced attenuation includes a silica glass core and a silica glass cladding. The silica glass core has substantially no germanium and includes a first core and a second core. The second core encloses the first core, the refractive index of the second core is larger than the refractive index of the first core, and the average value of halogen concentration of the second core is 5000 ppm or more. The silica glass cladding surrounds the second core and contains substantially no germanium. The refractive index of the cladding is smaller than the refractive index of the first core.

The optical fiber includes a core, the first cladding, and second cladding. The core is made of silica based glass containing Cl. The first cladding and the second cladding are made of silica based glass containing fluorine. The refractive index of the first cladding is lower than that of the core. The refractive index of the second cladding is lower than that of the core and higher than that of the first cladding. The second cladding is divided into an outer region having a uniform refractive index and an inner region having a refractive index higher than that of the outer region. The difference &#x394;P between the maximum refractive index of the inner region and the refractive index of the outer region is 0.02% to 0.10% in terms of relative refractive index with respect to pure silica based glass. The radial thickness R of the inner region is 10 &#x3bc;m to 25 &#x3bc;m.

An optical fiber containing an alkali metal and capable of reducing Rayleigh scattering loss is provided. An optical fiber has a core and a cladding made of silica glass and enclosing the core. The cladding contains fluorine and has a refractive index lower than the refractive index of the core. The core contains first group dopants selected from the group of Na element, K element, or a compound thereof at an average concentration of 0.2 ppm or more and 10 ppm or less. The core also contains second group dopants for reducing the viscosity of silica glass and having a diffusion coefficient of 1&#xd7;10cm/s or more and smaller than the diffusion coefficient of the first group dopants, by an average concentration of 0.2 ppm or more at a temperature of 2000&#xb0; C. to 2300&#xb0; C.

Optical fiber manufacturing method and optical fiber

An optical fiber containing an alkali metal element and exhibiting low attenuation as well as excellent radiation resistance is provided. The optical fiber of the present invention has a core region and a cladding region enclosing the core region. The core region contains alkali metal elements by an average concentration of 0.2 atomic ppm or more. The attenuation at a wavelength of 1550 nm after irradiating with the radiation of 0.10 Gy or more of cumulative absorbed dose increases by 0.02 dB/km or less as compared with the attenuation exhibited prior to radiation exposure.

An optical fiber preform which can be drawn into a low attenuation optical fiber is provided with a core portion and a cladding portion surrounding the core portion. The core portion includes a first core portion and a second core portion surrounding the first core portion. The cladding portion includes a first cladding portion surrounding the second core portion and a second cladding portion surrounding the first cladding portion. The first core portion contains an alkali metal element, the concentration of oxygen molecules contained in glass is 30 mol ppb or more and 200 mol ppb or less in a part of or entire region having an alkali metal atom concentration of 100 atomic ppm or more, and the concentration of oxygen molecules contained in glass is 10 mol ppb or less in a region having an alkali metal atom concentration of 50 atomic ppm or less.

Optical-fiber preform and method for manufacturing optical-fiber preform

A method includes (1) a thermal diffusion process for using an alkali metal salt raw material having an average particle size of 1 mm or less in diameter, supplying a vapor of the alkali metal salt produced by heating the alkali metal salt raw material together with a carrier gas to the inside of a silica-based glass pipe from one end side of the glass pipe, and heating the glass pipe using a heat source which relatively moves in a longitudinal direction of the glass pipe to cause an oxidation reaction of an alkali metal and thermally diffuse the alkali metal into an inner side of the glass pipe, (2) a collapsing process for collapsing the glass pipe after the thermal diffusion process to prepare a core rod; and (3) a cladding portion addition process for adding a cladding portion around the core rod prepared in the collapsing process.

Optical fiber preform manufacturing method, optical fiber preform, and optical fiber

Optical fiber and optical fiber preform

An optical fiber preform has a core portion having a first core portion including a central axis, a second core portion disposed around the first core portion, and a third core portion disposed around the second core portion. The first core portion contains 10 atomic ppm or more of an alkali metal and 10 to 600 atomic ppm of chlorine, the second core portion contains 10 atomic ppm or less of the alkali metal and 10 to 600 atomic ppm of chlorine, and the third core portion contains 10 atomic ppm or less of the alkali metal and 2,000 atomic ppm or more of chlorine. An optical fiber has a core region doped with an alkali metal and chlorine, wherein the minimum concentration of chlorine in the core region is 1,000 atomic ppm or more, and the average concentration of the alkali metal therein is 0.2 atomic ppm or more.

Growing community of inventors

Yokohama, Japan

Tetsuya Haruna