Fujikura Limited

Nippon Telegraph and Telephone Corporation

Osaka Prefecture University Public Corporation

Shimane University

Hokkaido University

University Public Corporation Osaka

National University Corporation Shimane University

Kentaro Ichii

Katsuhiro Takenaga

Shoji Tanigawa

Makoto Yamada

Shoichiro Matsuo

Hirotaka Ono

Tomofumi Arai

Koichi Harada

Hiroji Masuda

Naritoshi Yamada

Kenichi Ohmori

Takakazu Gotoh

Tsukasa Hosokawa

Kyouzou Tsujikawa

Teruno Nakaguma

Kunimasa Saitoh

Koji Omichi

Masakazu Ohashi

Kazuyuki Hayashi

Hideyuki Hosoya

Yoshihiro Terada

Tatsuya Kishi

Tomoyuki Fujita

Rintaro Kitahara

Shingo Matsushita

Koji Azegami

Nobuo Oozeki

Ken Katagiri

Keisuke Hirakawa

An optical fiber sensor includes: a central core disposed at a center of an optical fiber; and an outer peripheral core that spirally surrounds the central core. The effective refractive index nof the outer peripheral core is lower than the effective refractive index nof the central core. A ratio between the effective refractive index nand the effective refractive index nmatches a ratio between an optical path length of the central core and an optical path length of the outer peripheral core.

Optical fiber sensor

An optical fiber includes: a core that includes quartz glass doped with a core updopant; an inner cladding that includes quartz glass doped with a cladding updopant and a downdopant and that covers a circumferential surface of the core; and an outer cladding that includes quartz glass and that covers an outer circumferential surface of the inner cladding. A refractive index of the inner cladding is substantially equal to a refractive index of the outer cladding. The inner cladding contains the cladding updopant at a concentration such that a refractive index increase rate ascribed to the cladding updopant falls within a range of 0.25% to 0.5%.

Optical fiber

Provided is a method of manufacturing an optical fiber base material by an inside mounting method, including: a step of rotating and heating a glass tube fixed at two positions and supplying a gas into a through-hole of the glass tube, wherein in the step, the glass tube is warped so that an axis between respective fixed portions of the glass tube has a shape in which a catenary curve is reversed in the vertical direction.

Method of manufacturing optical fiber base material and method of manufacturing optical fiber

Provided is an optical coupler configured to cause an NA of light, which exits a taper fiber, to be smaller as compared with a conventional optical coupler. A taper fiber has a high refractive index part which is provided inside a core of the taper fiber and which has a refractive index smaller than a refractive index nof the core. An exit end surface of each GI fiber is bonded to an entrance end surface of the taper fiber so that at least a part of the exit end surface of the each GI fiber overlaps with a section of the high refractive index part. A relative refractive index difference of the taper fiber is smaller than 0.076%.

Optical coupler, laser device, and taper fiber

An optical fiber for amplification includes a core having an inner core and an outer core surrounding the outer circumferential surface of the inner core. The relative refractive index difference of the inner core to a cladding is smaller than the relative refractive index difference of the outer core to the cladding. The outer core is entirely doped with erbium. The theoretical cutoff wavelength of an LPmode light beam is a wavelength of 1,565 nm or more. The theoretical cutoff wavelength of an LPmode light beam is a wavelength of 1,530 nm or less. The theoretical cutoff wavelength of the LPmode light beam is a wavelength of 980 nm or less.

Optical fiber for amplification and optical fiber amplifier using the same

An amplification optical fiber operable to propagate light beams in a plurality of modes in a predetermined wavelength range through a core doped with a rare earth element, wherein Expression (1) is satisfied, where a cutoff wavelength of a propagated highest mode light beam is defined as &#x3bb;max, under conditions in which the cutoff wavelength of the highest mode light beam is defined as &#x3bb;c, a shortest wavelength of the wavelength range is defined as &#x3bb;min, and a cutoff wavelength of a second-highest mode light beam to the highest mode light beam is &#x3bb;min.&#x3bb;&#x3e;0.5 &#x3bb;min+0.5 &#x3bb;max&#x2003;&#x2003;(1).

Amplification optical fiber and optical fiber amplifier

A plurality of coresis disposed around the center axis of a first claddingin a state in which an inter-core distance &#x39b; of cores adjacent to each other is equal, a refractive index nof the coreis provided higher than a refractive index nof the first cladding, and the refractive index nof the first claddingis provided higher than a refractive index nof a second cladding. Moreover, 5.8&#x2266;&#x39b;/MFD(2&#x3bb;c/(&#x3bb;c+&#x3bb;op))&#x2266;8 is satisfied, where the inter-core distance is defined as &#x39b;, a mode field diameter of the core is defined as MFD, a cutoff wavelength is defined as &#x3bb;c, and a wavelength of communication light incident on the coreis defined as &#x3bb;op.

Amplifying optical fiber and optical amplifier

The first claddinghas a two-layer structure formed of a solid inner layerA passed through the center axis of the first claddingand an outer layerB enclosing the inner layerA and the plurality of coreswith no gap. A refractive index nof the coreis provided higher than refractive indexes nand nof the inner layerA and the outer layerB, the refractive indexes nA and nB of the inner layerA and the outer layerB are provided higher than a refractive index nof the second cladding, and the refractive index nof the inner layerA is provided lower than the refractive index nof the outer layerB.

An ytterbium-doped optical fiber includes: a core which contains at least ytterbium, aluminum, and phosphorus; and a cladding which encircles the core, wherein an aluminum oxide equivalent concentration of the aluminum in the core is 0.2 mol % or more, a diphosphorus pentaoxide equivalent concentration of the phosphorus is higher than the aluminum oxide equivalent concentration, and the core either does not contain germanium or contains less than 1.1 mol % of germanium in a germanium dioxide equivalent concentration.

Ytterbium-doped optical fiber, fiber laser and fiber amplifier

Provided is an ytterbium-doped optical fiber including a core containing at least ytterbium, aluminum and phosphorous and a clad surrounding the core, wherein a molar concentration of diphosphorus pentoxide with respect to phosphorus in the core is equal to a molar concentration of aluminum oxide with respect to aluminum in the core, wherein a ratio of a molar concentration of diphosphorus pentoxide with respect to phosphorus in the core to the molar concentration of ytterbium oxide with respect to ytterbium in the core is higher than or equal to 10 and lower than or equal to 30, and wherein a relative refractive index difference between the core and the clad is higher than or equal to 0.05% and lower than or equal to 0.30%.

Ytterbium-doped optical fiber

Provided is a manufacturing method for an optical fiber preform of which the core is doped with a rare earth element. The method includes: depositing glass particles within a silica tube by the modified chemical vapor deposition method, the glass particles mainly consisting of silicon dioxide; adding the rare earth element and aluminum to the glass particles within the silica tube by the solution doping method; heating the silica tube while flowing a phosphorous-containing gas into the silica tube to sinter the glass particles within the silica tube while adding the phosphorous; and heating and collapsing the silica tube to which the rare earth element, the aluminum, and the phosphorous are added.

Manufacturing method for optical fiber preform and optical fiber

Provided is a multi-cladding optical fiber which includes: a core with an average refractive index nand a cladding including an inner cladding with an average refractive index nformed on the periphery of the core, an intermediate cladding with an average refractive index nformed on the periphery of the inner cladding, and an outer cladding with an average refractive index nformed on the periphery of the intermediate cladding where n&#x3e;n&#x3e;n&#x3e;nTwo or more axisymmetric modes exist in the core at a wavelength of the signal light; the two or more axisymmetric modes including a fundamental mode and at least a high-order mode. When the fiber is bent at a predetermined bending diameter, the high-order mode in the core disperses within the inner cladding due to coupling with an inner cladding mode, so that only the fundamental mode substantially propagates through the core.

Multi-cladding optical fiber, optical fiber module, fiber laser, and fiber amplifier

A method for fabricating a porous silica preform includes the steps of supplying fuel gas for generating an oxyhydrogen flame to a glass synthesizing burner; supplying Gas A containing silicon and Gas B containing fluorine to the burner; synthesizing glass particles; and depositing the glass particles around a starting rod, in which when glass particles are deposited directly on the starting rod, a supply of Gas A and a supply of Gas B supplied to the burner are adjusted so that a ratio of the number of fluorine atoms to the number of silicon atoms in the gas supplied to the burner satisfies the following Formula (1):{(number of F atoms)/(number of Si atoms)}&#x2266;0.1&#x2003;&#x2003;(1).

Method for fabricating porous silica preform

An ytterbium-doped optical fiber of the present invention includes: a core which contains ytterbium, aluminum, and phosphorus and does not contain germanium; and a cladding which surrounds this core. The ytterbium concentration in the core in terms of ytterbium oxide is 0.09 to 0.68 mole percent. The molar ratio between the phosphorus concentration in the core in terms of diphosphorus pentoxide and the above ytterbium concentration in terms of ytterbium oxide is 3 to 30. The molar ratio between the aluminum concentration in the core in terms of aluminum oxide and the above ytterbium concentration in terms of ytterbium oxide is 3 to 32. The molar ratio between the above aluminum concentration in terms of aluminum oxide and the above phosphorus concentration in terms of diphosphorus pentoxide is 1 to 2.5.

Ytterbium-doped optical fiber, fiber laser, and fiber amplifier

A processing method for suppressing photodarkening in an Yb-doped optical fiber, comprising: a first step of preparing the Yb-doped optical fiber by doping a core with Yb, and irradiating at least one of a gamma ray, a X-ray, or an electron beam onto the Yb-doped optical fiber with an energy greater than a light to be transmitted through the optical fiber when a laser is being oscillated; a second step of measuring a loss spectrum of an infrared region of the optical fiber after the first step, and selecting an optical fiber with the loss in a specific wavelength falling within a predetermined range; and a third step of treating the optical fiber selected in the second step in an atmosphere containing hydrogen to obtain an Yb-doped optical fiber with suppressed photodarkening.

Growing community of inventors

Sakura, Japan

Kentaro Ichii