Patents by Inventor Kazuhide Nakajima
Kazuhide Nakajima 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: 10790905Abstract: The optical fiber according to the present disclosure is an optical fiber having a pure silica core which is a step index core through which an LPm1 mode with an effective area of 250 ?m2 or more is propagated by setting a relative refractive index difference to 0.60% or less, considering an effective cutoff condition, and only 2 or more modes or the LPm1 mode are propagated, with the optical fiber as the transmission line.Type: GrantFiled: July 4, 2017Date of Patent: September 29, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takayoshi Mori, Taiji Sakamoto, Takashi Yamamoto, Kazuhide Nakajima, Masaki Wada, Azusa Urushibara
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Patent number: 10782478Abstract: A differential mode attenuation compensator includes a first multi-mode optical fiber and a third multi-mode optical fiber in which a plurality of propagation modes propagate in a wavelength of a propagating optical signal; and a second multi-mode optical fiber including a core and a clad and arranged with a central axis aligned between the first multi-mode optical fiber and the third multi-mode optical fiber, in which each loss in the plurality of propagation modes is different in the first multi-mode optical fiber and the third multi-mode optical fiber.Type: GrantFiled: August 1, 2017Date of Patent: September 22, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Masaki Wada, Taiji Sakamoto, Takayoshi Mori, Shinichi Aozasa, Takashi Yamamoto, Kazuhide Nakajima
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Publication number: 20200225407Abstract: The optical fiber of the present invention includes a core, and a cladding that is provided on an outer periphery of the core and has a refractive index lower than a refractive index of the core region. In the optical fiber of the present invention, a V value representing a normalized frequency of an LP02 mode is greater than or equal to 4.8 and less than or equal to 6.4.Type: ApplicationFiled: July 31, 2018Publication date: July 16, 2020Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Azusa URUSHIBARA, Taiji SAKAMOTO, Masaki WADA, Takashi YAMAMOTO, Kazuhide NAKAJIMA, Takayoshi MORI
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Patent number: 10705291Abstract: An optical transmission system according to the present disclosure is a mode multiplexed optical transmission system using a multi-mode optical fiber in which a plurality of propagation modes propagate as a transmission line, the optical transmission system including an optical fiber transmission line (83) that includes an optical fiber with two or more propagation modes; and a plurality of mode converters (91) that are configured to generate mode coupling between at least one pair of the propagation modes, in which a variation in an installation interval of the plurality of mode converters (91) is equal to or less than a threshold value determined by the transmission line length (Lt) of the optical fiber transmission line (83).Type: GrantFiled: August 25, 2017Date of Patent: July 7, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Azusa Urushibara, Takayoshi Mori, Taiji Sakamoto, Masaki Wada, Takashi Yamamoto, Kazuhide Nakajima
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Publication number: 20200192022Abstract: An optical fiber having a graded index (GI)-type core refractive index profile in which a propagation mode can propagate Z (Z is an integer of 2 or more) or more is provided. In the optical fiber, an ?-parameter is a value in which a propagation constant mutual difference is 1000 rad/m or less in a propagation mode group of a mode group M (M is M=2p+l?1 and 3 or more when a propagation mode is denoted by LPlp).Type: ApplicationFiled: June 9, 2017Publication date: June 18, 2020Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Masaki WADA, Takayoshi MORI, Taiji SAKAMOTO, Takashi YAMAMOTO, Kazuhide NAKAJIMA
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Publication number: 20200116925Abstract: An optical fiber includes a core, a first clad that is provided on an outer circumferential portion of the core and has a refractive index lower than that of the core, and a second clad that is provided on an outer circumferential portion of the first clad and has a refractive index lower than that of the first clad. In the optical fiber, a mode field diameter at a wavelength of 1.55 ?m is equal to or greater than 11.5 ?m, a cutoff wavelength is equal to or less than 1.53 ?m, a bending loss at a bending radius of 30 mm and a wavelength of 1.625 ?m is equal to or less than 2.0 dB/100 turns, and a delay time of transmission light per unit length at a wavelength of 1.55 ?m is equal to or less than 4.876 ?s/km.Type: ApplicationFiled: July 3, 2018Publication date: April 16, 2020Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Yuto SAGAE, Kazuhide NAKAJIMA, Takashi MATSUI
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Patent number: 10620372Abstract: An alignment apparatus that can efficiently align an optical fiber, and an alignment method will be provided. According to the embodiments, the alignment apparatus that aligns an optical fiber comprises an acquisition unit, a calculation unit, and a rotation processing unit. The acquisition unit acquires one or more side images of the optical fiber. The calculation unit calculates correlation coefficients between the luminances of the one or more side images and those of one or more reference side images. The rotation processing unit rotates the optical fiber in the axis direction of the optical fiber so that the correlation coefficients peak.Type: GrantFiled: December 27, 2016Date of Patent: April 14, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi Matsui, Kazuhide Nakajima, Taiji Sakamoto, Koutaro Saito
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Patent number: 10585235Abstract: An optical connector is provided which includes at least one multi-core block fixing and holding a plurality of multi-core optical fibers in a state where a position in a direction orthogonal to an optical axis of each multi-core optical fiber and a rotation angle around the optical axis are in a predetermined state, and a ferrule including an accommodating portion accommodating the multi-core block.Type: GrantFiled: June 21, 2017Date of Patent: March 10, 2020Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Taiji Sakamoto, Takashi Matsui, Kazuhide Nakajima, Kotaro Saitoh
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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: 20190386748Abstract: The optical fiber according to the present disclosure is an optical fiber having a pure silica core which is a step index core through which an LPm1 mode with an effective area of 250 ?m2 or more is propagated by setting a relative refractive index difference to 0.60% or less, considering an effective cutoff condition, and only 2 or more modes or the LPm1 mode are propagated, with the optical fiber as the transmission line.Type: ApplicationFiled: July 4, 2017Publication date: December 19, 2019Applicant: Nippon Telegraph and Telephone CorporationInventors: Takayoshi MORI, Taiji SAKAMOTO, Takashi YAMAMOTO, Kazuhide NAKAJIMA, Masaki WADA, Azusa URUSHIBARA
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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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Publication number: 20190245317Abstract: An optical amplifier of the present disclosure includes an optical resonator that includes an amplification fiber capable of amplifying signal light having one or more propagation modes and resonates at least one propagation mode of the signal light amplified by the amplification fiber; an excitation light source that outputs excitation light for exciting the amplification fiber; and a multiplexer that multiplexes the signal light and the excitation light, in which the optical resonator includes a gain clamp setting unit which sets gain clamp for at least one propagation mode out of a plurality of propagation modes resonating in the optical resonator.Type: ApplicationFiled: October 25, 2017Publication date: August 8, 2019Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Masaki WADA, Shinichi AOZASA, Taiji SAKAMOTO, Takashi YAMAMOTO, Kazuhide NAKAJIMA, Takayoshi MORI
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Publication number: 20190196106Abstract: A differential mode attenuation compensator includes a first multi-mode optical fiber and a third multi-mode optical fiber in which a plurality of propagation modes propagate in a wavelength of a propagating optical signal; and a second multi-mode optical fiber including a core and a clad and arranged with a central axis aligned between the first multi-mode optical fiber and the third multi-mode optical fiber, in which each loss in the plurality of propagation modes is different in the first multi-mode optical fiber and the third multi-mode optical fiber.Type: ApplicationFiled: August 1, 2017Publication date: June 27, 2019Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Masaki WADA, Taiji SAKAMOTO, Takayoshi MORI, Shinichi AOZASA, Takashi YAMAMOTO, Kazuhide NAKAJIMA
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Publication number: 20190187365Abstract: An optical transmission system according to the present disclosure is a mode multiplexed optical transmission system using a multi-mode optical fiber in which a plurality of propagation modes propagate as a transmission line, the optical transmission system including an optical fiber transmission line (83) that includes an optical fiber with two or more propagation modes; and a plurality of mode converters (91) that are configured to generate mode coupling between at least one pair of the propagation modes, in which a variation in an installation interval of the plurality of mode converters (91) is equal to or less than a threshold value determined by the transmission line length (Lt) of the optical fiber transmission line (83).Type: ApplicationFiled: August 25, 2017Publication date: June 20, 2019Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Azusa URUSHIBARA, Takayoshi MORI, Taiji SAKAMOTO, Masaki WADA, Takashi YAMAMOTO, Kazuhide NAKAJIMA
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Publication number: 20190170931Abstract: An optical connector is provided which includes at least one multi-core block fixing and holding a plurality of multi-core optical fibers in a state where a position in a direction orthogonal to an optical axis of each multi-core optical fiber and a rotation angle around the optical axis are in a predetermined state, and a ferrule including an accommodating portion accommodating the multi-core block.Type: ApplicationFiled: June 21, 2017Publication date: June 6, 2019Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Taiji SAKAMOTO, Takashi MATSUI, Kazuhide NAKAJIMA, Kotaro SAITOH
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Publication number: 20180372954Abstract: An alignment apparatus that can efficiently align an optical fiber, and an alignment method will be provided. According to the embodiments, the alignment apparatus that aligns an optical fiber comprises an acquisition unit, a calculation unit, and a rotation processing unit. The acquisition unit acquires one or more side images of the optical fiber. The calculation unit calculates correlation coefficients between the luminances of the one or more side images and those of one or more reference side images. The rotation processing unit rotates the optical fiber in the axis direction of the optical fiber so that the correlation coefficients peak.Type: ApplicationFiled: December 27, 2016Publication date: December 27, 2018Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Takashi MATSUI, Kazuhide NAKAJIMA, Taiji SAKAMOTO, Koutaro SAITO
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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