Patents by Inventor Kyozo Tsujikawa
Kyozo Tsujikawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 11860405Abstract: An object of the present invention is to provide an HAF having a structure in which the number of air holes is decreased to be smaller than that of a PCF and Rayleigh scattering loss may be more reduced than that in the existing HAF.Type: GrantFiled: September 18, 2019Date of Patent: January 2, 2024Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Saki Nozoe, Nobutomo Hanzawa, Yuto Sagae, Kazuhide Nakajima, Kyozo Tsujikawa
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Patent number: 11815421Abstract: An objective is to provide an acoustic mode propagation speed measurement method and an acoustic mode propagation speed measurement device capable of measuring a propagation speed of an acoustic mode without cutting or processing an optical fiber wire. According to the present invention, an acoustic mode propagation speed measurement method includes: acquiring a frequency shift spectrum of Brillouin scattered light generated in an optical fiber; fitting the frequency shift spectrum using a Gauss function; acquiring a spectral full-width at half maximum w from a fitted curve using the Gauss function; and calculating a propagation speed VA of an acoustic mode of the optical fiber by substituting the acquired spectral full-width at half maximum w into a linear function of the spectral full-width at half maximum w and the propagation speed VA of the acoustic mode.Type: GrantFiled: February 19, 2020Date of Patent: November 14, 2023Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Yuto Sagae, Takashi Matsui, Kyozo Tsujikawa, Kazuhide Nakajima
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Publication number: 20220334307Abstract: An object of the present invention is to provide an HAF having a structure in which the number of air holes is decreased to be smaller than that of a PCF and Rayleigh scattering loss may be more reduced than that in the existing HAF.Type: ApplicationFiled: September 18, 2019Publication date: October 20, 2022Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Saki NOZOE, Nobutomo HANZAWA, Yuto SAGAE, Kazuhide NAKAJIMA, Kyozo TSUJIKAWA
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Publication number: 20220276430Abstract: An object of the present invention is to provide a multi-core optical fiber that can prevent an increase in bending loss even when a distance between a peripheral core and a cladding boundary is decreased, and can improve a bending loss characteristic in a state where an influence on a cutoff wavelength and a mode field diameter is small, and a design method thereof.Type: ApplicationFiled: July 21, 2020Publication date: September 1, 2022Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Taiji SAKAMOTO, Kazuhide NAKAJIMA, Takashi MATSUI, Kyozo TSUJIKAWA, Kunimasa SAITOH, Takeshi FUJISAWA
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Publication number: 20220170817Abstract: An objective is to provide an acoustic mode propagation speed measurement method and an acoustic mode propagation speed measurement device capable of measuring a propagation speed of an acoustic mode without cutting or processing an optical fiber wire. According to the present invention, an acoustic mode propagation speed measurement method includes: acquiring a frequency shift spectrum of Brillouin scattered light generated in an optical fiber; fitting the frequency shift spectrum using a Gauss function; acquiring a spectral full-width at half maximum w from a fitted curve using the Gauss function; and calculating a propagation speed VA of an acoustic mode of the optical fiber by substituting the acquired spectral full-width at half maximum w into a linear function of the spectral full-width at half maximum w and the propagation speed VA of the acoustic mode.Type: ApplicationFiled: February 19, 2020Publication date: June 2, 2022Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Yuto SAGAE, Takashi MATSUI, Kyozo TSUJIKAWA, Kazuhide NAKAJIMA
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Patent number: 11237322Abstract: An optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.Type: GrantFiled: September 16, 2019Date of Patent: February 1, 2022Assignees: FURUKAWA ELECTRIC CO., LTD., NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Shinichi Arai, Harumi Inaba, Shigeto Matsumoto, Takeshi Yagi, Shinichi Aozasa, Kyozo Tsujikawa, Kazuhide Nakajima
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Patent number: 10871648Abstract: An optical fiber design method according to the present invention is a design method of a photonic crystal fiber having a plurality of holes arranged in the optical fiber along a longitudinal direction, in which a required effective cross-sectional area is calculated from a light wavelength, a transmission distance, and output power such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding, and a fiber structure (hole diameter and hole interval) corresponding to the effective cross-sectional area is calculated.Type: GrantFiled: November 17, 2016Date of Patent: December 22, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kazuhide Nakajima, Kyozo Tsujikawa, Fumihiko Yamamoto
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Patent number: 10816722Abstract: An object is to provide a beam propagating method capable of satisfying desired output power and a desired propagation distance and a required condition of beam quality and a method of designing an optical fiber designing the structure of an optical fiber. According to the present invention, an effective core cross-sectional area Aeff is calculated based on desired specification values and, by appropriately adjusting the structure of an optical fiber satisfying the effective core cross-sectional area and the number of modes to be propagated, the structure of the optical fiber is determined. In this way, by controlling the excitation ratio of a high-order mode at the time of coupling laser light in the optical fiber designed as above, light of high-output laser can be propagated a long distance with the beam quality maintained.Type: GrantFiled: March 18, 2016Date of Patent: October 27, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kyozo Tsujikawa, Fumihiko Yamamoto, Nobutomo Hanzawa
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Patent number: 10545333Abstract: A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.Type: GrantFiled: November 17, 2016Date of Patent: January 28, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kazuhide Nakajima, Kyozo Tsujikawa, Fumihiko Yamamoto
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Patent number: 10539784Abstract: A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.Type: GrantFiled: July 10, 2019Date of Patent: January 21, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kazuhide Nakajima, Kyozo Tsujikawa, Fumihiko Yamamoto
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Publication number: 20200012042Abstract: An optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.Type: ApplicationFiled: September 16, 2019Publication date: January 9, 2020Applicants: FURUKAWA ELECTRIC CO., LTD., NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Shinichi ARAI, Harumi Inaba, Shigeto Matsumoto, Takeshi Yagi, Shinichi Aozasa, Kyozo Tsujikawa, Kazuhide Nakajima
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Publication number: 20190339513Abstract: A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.Type: ApplicationFiled: July 10, 2019Publication date: November 7, 2019Inventors: Takashi MATSUI, Kazuhide NAKAJIMA, Kyozo TSUJIKAWA, Fumihiko YAMAMOTO
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Patent number: 10444428Abstract: An optical fiber that is a photonic crystal fiber in which a plurality of holes is arranged along a longitudinal direction of the optical fiber, having a predetermined bending radius R determined according to a transmission distance L of the optical fiber and optical power output from the optical fiber, and having an inter-hole distance ? and a ratio d/? between a hole diameter d and the inter-hole distance ? such that light of a predetermined number of modes is transmitted and a bending loss of the light of a fundamental mode with the predetermined bending radius R is equal to or smaller than a predetermined value.Type: GrantFiled: March 3, 2016Date of Patent: October 15, 2019Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kyozo Tsujikawa, Fumihiko Yamamoto, Nobutomo Hanzawa
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Patent number: 10310177Abstract: An object of the present invention is to provide a structure of an optical fiber capable of satisfying desired requirements of an output power, a propagation distance, and a beam quality. In the design of the PCF of the present invention, the PCF has air holes having diameters d and intervals ? in an overlapping region where a region of Aeff of a desired value or more and a cutoff region in a desired higher-order mode overlap each other on a graph where the horizontal axis represents d/? and the vertical axis represents ?, so that it is possible to sufficiently cut off the mode which is the desired higher-order mode or more, and thus, it is possible to select a region where the Aeff is large.Type: GrantFiled: March 22, 2016Date of Patent: June 4, 2019Assignee: Nippon Telegraph and Telephone CorporationInventors: Takashi Matsui, Kyozo Tsujikawa, Fumihiko Yamamoto, Nobutomo Hanzawa
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Publication number: 20190004246Abstract: An optical fiber that is a photonic crystal fiber in which a plurality of holes is arranged along a longitudinal direction of the optical fiber, having a predetermined bending radius R determined according to a transmission distance L of the optical fiber and optical power output from the optical fiber, and having an inter-hole distance ? and a ratio d/? between a hole diameter d and the inter-hole distance ? such that light of a predetermined number of modes is transmitted and a bending loss of the light of a fundamental mode with the predetermined bending radius R is equal to or smaller than a predetermined value.Type: ApplicationFiled: March 3, 2016Publication date: January 3, 2019Inventors: Takashi MATSUI, Kyozo TSUJIKAWA, Fumihiko YAMAMOTO, Nobutomo HANZAWA
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Publication number: 20180341104Abstract: An optical fiber design method according to the present invention is a design method of a photonic crystal fiber having a plurality of holes arranged in the optical fiber along a longitudinal direction, in which a required effective cross-sectional area is calculated from a light wavelength, a transmission distance, and output power such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding, and a fiber structure (hole diameter and hole interval) corresponding to the effective cross-sectional area is calculated.Type: ApplicationFiled: November 17, 2016Publication date: November 29, 2018Inventors: Takashi MATSUI, Kazuhide NAKAJIMA, Kyozo TSUJIKAWA, Fumihiko YAMAMOTO
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Publication number: 20180321439Abstract: A photonic crystal fiber according to the present invention has a plurality of holes arranged in the optical fiber along a longitudinal direction, in which the holes are arranged such that, in a cross section, a hole ratio which is an area of the holes per unit area is larger in a central side than in an outer side in a portion corresponding to a cladding and that a wide core area can be obtained while the number of modes that can be propagated is limited to several. Moreover, in a high-power optical transmission system according to the present invention, the amount of axis misalignment between the central axis of a laser oscillator and the central axis of the photonic crystal fiber is less than or equal to a certain amount.Type: ApplicationFiled: November 17, 2016Publication date: November 8, 2018Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi MATSUI, Kazuhide NAKAJIMA, Kyozo TSUJIKAWA, Fumihiko YAMAMOTO
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Publication number: 20180172902Abstract: An object of the present invention is to provide a structure of an optical fiber capable of satisfying desired requirements of an output power, a propagation distance, and a beam quality. In the design of the PCF of the present invention, the PCF has air holes having diameters d and intervals ? in an overlapping region where a region of Aeff of a desired value or more and a cutoff region in a desired higher-order mode overlap each other on a graph where the horizontal axis represents d/? and the vertical axis represents ?, so that it is possible to sufficiently cut off the mode which is the desired higher-order mode or more, and thus, it is possible to select a region where the Aeff is large.Type: ApplicationFiled: March 22, 2016Publication date: June 21, 2018Inventors: Takashi MATSUI, Kyozo TSUJIKAWA, Fumihiko YAMAMOTO, Nobutomo HANZAWA
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Publication number: 20180052278Abstract: An object is to provide a beam propagating method capable of satisfying desired output power and a desired propagation distance and a required condition of beam quality and a method of designing an optical fiber designing the structure of an optical fiber. According to the present invention, an effective core cross-sectional area Aeff is calculated based on desired specification values and, by appropriately adjusting the structure of an optical fiber satisfying the effective core cross-sectional area and the number of modes to be propagated, the structure of the optical fiber is determined. In this way, by controlling the excitation ratio of a high-order mode at the time of coupling laser light in the optical fiber designed as above, light of high-output laser can be propagated a long distance with the beam quality maintained.Type: ApplicationFiled: March 18, 2016Publication date: February 22, 2018Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kyozo Tsujikawa, Fumihiko Yamamoto, Nobutomo Hanzawa