Patents by Inventor Taiji SAKAMOTO

Taiji SAKAMOTO 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).

  • Publication number: 20220360358
    Abstract: An object of the present invention is to provide an optical transmission system capable of controlling a transmission capacity and a signal processing load of a MIMO equalizer, without depending on the number of propagation modes of the optical fiber.
    Type: Application
    Filed: September 17, 2019
    Publication date: November 10, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Taiji SAKAMOTO, Masaki WADA, Takashi YAMAMOTO, Kazuhide NAKAJIMA
  • Publication number: 20220344888
    Abstract: An objective of the present invention is to provide an amplification fiber having a cladding excitation configuration that improves amplification efficiency and an optical amplifier. An amplification fiber (10) according to the present invention is a multi-core amplification fiber having, from one end (E1) to the other end (EE), a plurality of cores (11b) in a cladding (11a), and a total distance from the one end (E1) to the other end (EE) in which rare earth ions are doped differs depending on the types of cores (11b). The cores (11b) are preferably disposed such that the cores of the same type are not adjacent to each other. By arranging the types of the cores in this manner, requirements for inter-core crosstalk can be mitigated since the bands of signal light in the adjacent cores are different. As a result, a density of cladding excitation light can be increased by shortening the inter-core distance, and thus the amplification efficiency can be improved.
    Type: Application
    Filed: September 26, 2019
    Publication date: October 27, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Shinichi AOZASA, Taiji SAKAMOTO, Kazuhide NAKAJIMA, Masaki WADA
  • Publication number: 20220337020
    Abstract: An object is to provide an optical amplifier with a cladding pumped configuration that improves amplification efficiency. The optical amplifier according to the present invention includes a pump light conversion fiber 11 that converts first pump light L1 with a first wavelength propagating in a cladding into second pump light L2 with a second wavelength, an amplification fiber 13 that is connected to the pump light conversion fiber 11 and optically amplifies signal light Ls with the second pump light L2 supplied to the cladding from the pump light conversion fiber 11, and an oscillator 12 that causes the second pump light L2 to be reflected on two reflectors 15 and to reciprocate within the claddings of the pump light conversion fiber 11 and the amplification fiber 13 to cause laser oscillation of the second pump light L2.
    Type: Application
    Filed: September 26, 2019
    Publication date: October 20, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Shinichi AOZASA, Taiji SAKAMOTO, Kazuhide NAKAJIMA, Masaki WADA
  • Publication number: 20220337025
    Abstract: An objective of the present invention is to provide an optical amplifier having a cladding excitation configuration that improves amplification efficiency.
    Type: Application
    Filed: September 26, 2019
    Publication date: October 20, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Shinichi AOZASA, Taiji SAKAMOTO, Kazuhide NAKAJIMA, Masaki WADA
  • Publication number: 20220337016
    Abstract: An objective is to provide an optical amplifier having a core excitation configuration that improves amplification efficiency. An optical amplifier according to the present invention includes an excitation light conversion fiber 11 that absorbs first excitation light L1 propagating in a cladding and having a first wavelength and emits, into a core, spontaneous emission light having a second wavelength, an oscillator 12 for causing the spontaneous emission light to be reflected on two reflectors 15 to reciprocate the light within the core of the excitation light conversion fiber 11 and laser-oscillating second excitation light L2 having the second wavelength, and an amplification fiber 13 that is connected to the excitation light conversion fiber 11 and amplifies signal light with the second excitation light L2 supplied from the excitation light conversion fiber 11 to the core.
    Type: Application
    Filed: September 26, 2019
    Publication date: October 20, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Shinichi AOZASA, Taiji SAKAMOTO, Kazuhide NAKAJIMA, Masaki WADA
  • Patent number: 11454757
    Abstract: A planar waveguide having M×N number of cores and to which M number of fibers having N number of cores are connected. In the planar waveguide, in a connecting end surface of the planar waveguide to which the fibers are connected, P number of fibers having Q number of cores are connected, M×N is equal to P×Q, the planar waveguide includes a plurality of the cores arranged in a horizontal direction at the same height position in the planar waveguide, and a laminated structure having the cores at different positions in a height direction, so as to be aligned with the cores of the fibers connected to the connecting end surface, and the positions of the M×N number of cores are constant in the height direction, and change only in the horizontal direction.
    Type: Grant
    Filed: July 11, 2019
    Date of Patent: September 27, 2022
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Taiji Sakamoto, Yoshiteru Abe, Kazuhide Nakajima
  • Publication number: 20220294537
    Abstract: An object of the present invention is to provide an optical transmission system capable of easily controlling a transmission capacity and an optical signal quality even if a MIMO equalizer is provided. The optical transmission system according to the present invention is provided with an N×M MIMO equalizer, includes receivers (N units) equal in number to the spatial multiplexing order L of an optical fiber, and changes the number M of the signal beams of light transmitted through the optical fiber in the range of the spatial multiplex order L or less. The adjustment of the number M of signal beams of light makes it possible to adjust a transmission capacity and a signal quality of the optical transmission system even after construction of the transmission line.
    Type: Application
    Filed: August 23, 2019
    Publication date: September 15, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Taiji SAKAMOTO, Masaki WADA, Takashi YAMAMOTO, Kazuhide NAKAJIMA
  • Publication number: 20220294536
    Abstract: An objective of the present invention is to provide an optical communication system and an optical communication method that can reduce even a delay generated in processing of obtaining a transfer function for correcting distortion in digital coherent transmission. In the optical communication system according to the present invention, pilot data for estimating a transfer function for a transmission channel is transmitted through a transmission channel with a short transmission delay time, a transfer function of the transmission channel is estimated before receiving transmission data, and the transfer function is applied to other transmission channels.
    Type: Application
    Filed: August 19, 2019
    Publication date: September 15, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Yuto SAGAE, Takashi MATSUI, Taiji SAKAMOTO, Kazuhide NAKAJIMA
  • Publication number: 20220276430
    Abstract: 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: Application
    Filed: July 21, 2020
    Publication date: September 1, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Taiji SAKAMOTO, Kazuhide NAKAJIMA, Takashi MATSUI, Kyozo TSUJIKAWA, Kunimasa SAITOH, Takeshi FUJISAWA
  • Publication number: 20220214496
    Abstract: An object is to provide a multi-core configuration for acquiring a random mode coupling in a case of an arbitrary core refractive index. A multi-core optical fiber according to the present invention is an optical fiber in which two or more core regions are arranged in a clad region having a refractive index at a minimum core interval ? smaller than a refractive index of the cores, a configuration of the cores is that including one propagation mode, and the core configuration and the core interval are adjusted so that an inter-mode coupling coefficient between adjacent cores is within a range from 0.73 to 120 m?1.
    Type: Application
    Filed: April 6, 2020
    Publication date: July 7, 2022
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Taiji SAKAMOTO, Kazuhide NAKAJIMA, Masaki WADA, Shinichi AOZASA, Takashi YAMAMOTO
  • Patent number: 11196227
    Abstract: 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: Grant
    Filed: October 25, 2017
    Date of Patent: December 7, 2021
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Masaki Wada, Shinichi Aozasa, Taiji Sakamoto, Takashi Yamamoto, Kazuhide Nakajima, Takayoshi Mori
  • Patent number: 11156767
    Abstract: 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: Grant
    Filed: July 31, 2018
    Date of Patent: October 26, 2021
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Azusa Urushibara, Taiji Sakamoto, Masaki Wada, Takashi Yamamoto, Kazuhide Nakajima, Takayoshi Mori
  • Publication number: 20210263213
    Abstract: A planar waveguide having M×N number of cores and to which M number of fibers having N number of cores are connected. In the planar waveguide, in a connecting end surface of the planar waveguide to which the fibers are connected, P number of fibers having Q number of cores are connected, M×N is equal to P×Q, the planar waveguide includes a plurality of the cores arranged in a horizontal direction at the same height position in the planar waveguide, and a laminated structure having the cores at different positions in a height direction, so as to be aligned with the cores of the fibers connected to the connecting end surface, and the positions of the M×N number of cores are constant in the height direction, and change only in the horizontal direction.
    Type: Application
    Filed: July 11, 2019
    Publication date: August 26, 2021
    Inventors: Taiji Sakamoto, Yoshiteru Abe, Kazuhide Nakajima
  • Patent number: 10790905
    Abstract: 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: Grant
    Filed: July 4, 2017
    Date of Patent: September 29, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Takayoshi Mori, Taiji Sakamoto, Takashi Yamamoto, Kazuhide Nakajima, Masaki Wada, Azusa Urushibara
  • Patent number: 10782478
    Abstract: 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: Grant
    Filed: August 1, 2017
    Date of Patent: September 22, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Masaki Wada, Taiji Sakamoto, Takayoshi Mori, Shinichi Aozasa, Takashi Yamamoto, Kazuhide Nakajima
  • Publication number: 20200225407
    Abstract: 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: Application
    Filed: July 31, 2018
    Publication date: July 16, 2020
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Azusa URUSHIBARA, Taiji SAKAMOTO, Masaki WADA, Takashi YAMAMOTO, Kazuhide NAKAJIMA, Takayoshi MORI
  • Patent number: 10705291
    Abstract: 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: Grant
    Filed: August 25, 2017
    Date of Patent: July 7, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Azusa Urushibara, Takayoshi Mori, Taiji Sakamoto, Masaki Wada, Takashi Yamamoto, Kazuhide Nakajima
  • Publication number: 20200192022
    Abstract: 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: Application
    Filed: June 9, 2017
    Publication date: June 18, 2020
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Masaki WADA, Takayoshi MORI, Taiji SAKAMOTO, Takashi YAMAMOTO, Kazuhide NAKAJIMA
  • Patent number: 10620372
    Abstract: 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: Grant
    Filed: December 27, 2016
    Date of Patent: April 14, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Takashi Matsui, Kazuhide Nakajima, Taiji Sakamoto, Koutaro Saito
  • Patent number: 10585235
    Abstract: 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: Grant
    Filed: June 21, 2017
    Date of Patent: March 10, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Taiji Sakamoto, Takashi Matsui, Kazuhide Nakajima, Kotaro Saitoh