Patents by Inventor Toshiyuki Tokura

Toshiyuki Tokura 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: 20100239263
    Abstract: A control-target-value setting unit sets a control target value corresponding to the number of multiplexed wavelengths measured by a number-of-multiplexed-wavelengths measuring unit. A controller controls the variable optical attenuator based on the control target value. An optical amplifier performs an optical amplification with a constant gain regardless of power of a wavelength-multiplexed light. The controller performs feedback control of the variable optical attenuator such that a result of measurement of the total power of the wavelength-multiplexed light coincides with the control target value.
    Type: Application
    Filed: May 25, 2006
    Publication date: September 23, 2010
    Applicant: MITSUBISHI ELECTRIC CORPORATION
    Inventors: Toshiyuki Tokura, Katsuhiro Shimizu, Kazuyuki Ishida, Kuniaki Motoshima
  • Patent number: 7768698
    Abstract: A Raman amplifier includes a pumping light source, an optical coupler, and a Raman amplifier medium. The pumping light source outputs a pumping light that is intensity-modulated with a frequency equal to or higher than 100 megahertz. The optical coupler couples the pumping light with a carrier light. The Raman amplification medium is pumped by the pumping light to amplify the carrier light. The Raman amplification medium has characteristics of a low dispersion and a small difference between propagation times of the carrier light and the pumping light.
    Type: Grant
    Filed: August 30, 2004
    Date of Patent: August 3, 2010
    Assignees: Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology, Mitsubishi Electric Corporation
    Inventors: Toshiyuki Tokura, Katsuhiro Shimizu, Tasuku Fujieda, Ken'ichi Asakawa, Hitoshi Mikada, Katsuyoshi Kawaguchi
  • Patent number: 7539413
    Abstract: The present invention discloses a submarine observation system in which a plurality of carrier lights assigned to each submarine observation equipment is transmitted from a land terminal apparatus to an optical submarine cable (down-going) by using a WDM transmission. In the submarine observation equipment, only a prescribed carrier light is demultiplexed by an optical demultiplexer, an observation signal indicating an observation result is generated by an observation device, intensity of the carrier light demultiplexed by the optical demultiplexer is modulated by an optical amplifier based on an observation signal, and the modulated carrier light is multiplexed by an optical multiplexer. The multiplexed carrier light is output to the optical submarine cable (up-going) to be returned to the land terminal apparatus being the transmission station.
    Type: Grant
    Filed: March 14, 2005
    Date of Patent: May 26, 2009
    Assignees: Mitsubishi Denki Kabushiki Kaisha, Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology
    Inventors: Hiroaki Munehira, Junichi Nakagawa, Toshiyuki Tokura, Kenichi Asakawa, Hitoshi Mikada, Katsuyoshi Kawaguchi
  • Publication number: 20080013161
    Abstract: A Raman amplifier includes a pumping light source, an optical coupler, and a Raman amplifier medium. The pumping light source outputs a pumping light that is intensity-modulated with a frequency equal to or higher than 100 megahertz. The optical coupler couples the pumping light with a carrier light. The Raman amplification medium is pumped by the pumping light to amplify the carrier light. The Raman amplification medium has characteristics of a low dispersion and a small difference between propagation times of the carrier light and the pumping light.
    Type: Application
    Filed: August 30, 2004
    Publication date: January 17, 2008
    Applicants: INDEPENDENT ADMINISTRATIVE INSTITUTION, JAPAN AGENCY FOR MARINE-EARTH SCIENCE AND TECHNOLOGY, MITSUBISHI ELECTRIC CORPORATION
    Inventors: Toshiyuki Tokura, Katsuhiro Shimizu, Tasuku Fujieda, Ken'ichi Asakawa, Hitoshi Mikada, Katsuyoshi Kawaguchi
  • Patent number: 7218441
    Abstract: A laser light source outputs a virtually linearly-polarized light beam that has plural mode components arranged at an interval of an almost equal angular frequency. A polarization dispersion device is connected to the laser light source in such a way that a polarization axis of the polarization dispersion device is at 45° with respect to a polarization axis of the light beam output from the laser light source. This polarization dispersion device effects on the light beam output from the laser light source a polarization mode dispersion that is not in the vicinity of (2?/??), where ?? is a mode interval angular frequency.
    Type: Grant
    Filed: January 27, 2003
    Date of Patent: May 15, 2007
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Toshiyuki Tokura, Taichi Kogure, Takashi Sugihara, Kuniaki Motoshima
  • Patent number: 7068421
    Abstract: An optical fiber propagates and amplifies a second signal light that is a wavelength-multiplexed signal of a first signal light of a plurality of wavelengths and a reference light that is out of a wavelength range of amplification. An excitation light source outputs an excitation light for amplifying the second signal light. A beam splitter splits a portion of the second signal light into the first signal light and the reference light. A signal light level detecting unit detects a level of the first signal light. A reference light level detecting unit detects a level of the reference light. A signal level setting unit calculates a target value for constantly maintaining a Raman gain, and controls the output level of the excitation light in such a way that the first signal level matches with the target value.
    Type: Grant
    Filed: September 4, 2003
    Date of Patent: June 27, 2006
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Toshiyuki Tokura, Taichi Kogure, Satoshi Kajiya, Takashi Mizuochi
  • Publication number: 20050259264
    Abstract: The present invention discloses a submarine observation system in which a plurality of carrier lights assigned to each submarine observation equipment is transmitted from a land terminal apparatus to an optical submarine cable (down-going) by using a WDM transmission. In the submarine observation equipment, only a prescribed carrier light is demultiplexed by an optical demultiplexer, an observation signal indicating an observation result is generated by an observation device, intensity of the carrier light demultiplexed by the optical demultiplexer is modulated by an optical amplifier based on an observation signal, and the modulated carrier light is multiplexed by an optical multiplexer. The multiplexed carrier light is output to the optical submarine cable (up-going) to be returned to the land terminal apparatus being the transmission station.
    Type: Application
    Filed: March 14, 2005
    Publication date: November 24, 2005
    Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA, Japan Agency for Marine-Earth Science and Tech.
    Inventors: Hiroaki Munehira, Junichi Nakagawa, Toshiyuki Tokura, Kenichi Asakawa, Hitoshi Mikada, Katsuyoshi Kawaguchi
  • Publication number: 20050099676
    Abstract: An optical fiber propagates and amplifies a second signal light that is a wavelength-multiplexed signal of a first signal light of a plurality of wavelengths and a reference light that is out of a wavelength range of amplification. An excitation light source outputs an excitation light for amplifying the second signal light. A beam splitter splits a portion of the second signal light into the first signal light and the reference light. A signal light level detecting unit detects a level of the first signal light. A reference light level detecting unit detects a level of the reference light. A signal level setting unit calculates a target value for constantly maintaining a Raman gain, and controls the output level of the excitation light in such a way that the first signal level matches with the target value.
    Type: Application
    Filed: September 4, 2003
    Publication date: May 12, 2005
    Inventors: Toshiyuki Tokura, Taichi Kogure, Satoshi Kajiya, Takashi Mizuochi
  • Publication number: 20040165254
    Abstract: In an non-polarized pump light source (5), a laser light source (1) transmits a virtually linearly-polarized light beam that has plural mode components arranged at an interval of an almost equal angular frequency. The transmitted light beam of the laser light source (1) is connected with a polarization dispersion device (3) in such a way that the polarization axes of the transmitted light beam and the polarization dispersion device (3) meet to form a 45° angle. In the polarization dispersion device (3), when the mode interval angular frequency is considered to be &Dgr;&ohgr;, the polarization mode dispersion that is not in the vicinity of (2&pgr;/&Dgr;&ohgr;) is effected on the incident light from the laser light source (1). As a result, though the optical path difference between the two polarization modes becomes less than the coherent length, an effectively non-polarizing light is transmitted as a pump light from the non-polarized pump light source (5).
    Type: Application
    Filed: December 30, 2003
    Publication date: August 26, 2004
    Inventors: Toshiyuki Tokura, Taichi Kogure, Takashi Sugihara, Kuniaki Motoshima