Patents by Inventor Hidenori Nakada
Hidenori Nakada 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: 8854716Abstract: An input/output port, a birefringent element, variable polarization rotator, and a reflector are arranged along an optical axis in the order named. The variable polarization rotator includes permanent magnets for applying a fixed magnetic field to a Faraday rotator in an in-plane direction to magnetically saturate the Faraday rotator and a solenoid coil for applying a variable magnetic field to the Faraday rotator in a direction of the optical axis. A fixed magnetic field is applied in the <211> direction, in which the Faraday rotator is likely to be magnetically saturated. The Faraday rotator can be saturated with a low magnetic field of about 100 Oe. The permanent magnets may employ ferrite permanent magnets, which have weak magnetic forces. A variable magnetic field may also be reduced. Therefore, an air-core coil can be used.Type: GrantFiled: June 27, 2011Date of Patent: October 7, 2014Assignee: FDK CorporationInventors: Hiroaki Ono, Hidenori Nakada, Hirotaka Kawai, Yuko Ota, Taro Nakamura
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Publication number: 20130120824Abstract: An input/output port, a birefringent element, variable polarization rotator, and a reflector are arranged along an optical axis in the order named. The variable polarization rotator includes permanent magnets for applying a fixed magnetic field to a Faraday rotator in an in-plane direction to magnetically saturate the Faraday rotator and a solenoid coil for applying a variable magnetic field to the Faraday rotator in a direction of the optical axis. A fixed magnetic field is applied in the <211> direction, in which the Faraday rotator is likely to be magnetically saturated. The Faraday rotator can be saturated with a low magnetic field of about 100 Oe. The permanent magnets may employ ferrite permanent magnets, which have weak magnetic forces. A variable magnetic field may also be reduced. Therefore, an air-core coil can be used.Type: ApplicationFiled: June 27, 2011Publication date: May 16, 2013Applicant: FDK CORPORATIONInventors: Hiroaki Ono, Hidenori Nakada, Hirotaka Kawai, Yuko Ota, Taro Nakamura
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Patent number: 7142362Abstract: A low-cost compact optical attenuator structure has an input port and an output port for optical signals arranged side by side; a reflecting member arranged to face both ports to reverse light from the input side on an optical path folded 180°; a birefringence crystal splits incident light into two polarization components, a converging lens converges the incident light, a fixed Faraday rotator having a variable rotation angle arranged in that order in the optical path. The partial reflecting member that transmits a portion of incident light to the rear side thereof, an optical sensor at the rear side of the reflecting member, optical guide means guide only the transmitted light from the input port side to the optical sensor, and optical detection signals of the optical sensor are used as optical input monitoring signals.Type: GrantFiled: September 17, 2004Date of Patent: November 28, 2006Assignee: FDK CorporationInventors: Hidenori Nakada, Shusuke Wada, Keisuke Ikeda, Yuko Ota
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Patent number: 7050216Abstract: A variable optical filter comprises a first polarizer, a first phase difference element operable to generate a phase difference, a variable Faraday rotator operable to impart a variable Faraday rotation, a second phase difference element operable to generate a phase difference, and a second polarizer, wherein said polarizers, said variable Faraday rotator, and said phase difference elements are arranged in the mentioned order along the optical axis, and wherein when the angles formed by the optic axes of said first and second phase difference elements and the transmitted polarization azimuth of the first polarizer are assumed respectively to be ?1 and ?2, these ?1 and ?2 are set to different angles.Type: GrantFiled: December 10, 2004Date of Patent: May 23, 2006Assignees: Fujitsu Limited, FDK CorporationInventors: Nobuhiro Fukushima, Hidenori Nakada, Tsugio Tokumasu, Yuko Ota
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Patent number: 7024073Abstract: A reflection-type variable optical attenuator comprises: a main attenuator unit including a first birefringent crystal plate, a Faraday rotational angle varying unit, and a second birefringent crystal plate arranged in this order; an input port and an output port that are arranged on a side of one end of the main attenuator unit; and a two-point reflection-type optical path varying reflector that is arranged on a side of the other end of the main attenuator unit. Light that comes in from the input port makes a round trip in the main attenuator unit and goes out through the output port.Type: GrantFiled: September 20, 2002Date of Patent: April 4, 2006Assignee: FDK CorporationInventors: Teruhisa Sahashi, Hidenori Nakada, Shohei Abe, Isao Kojima, Keisuke Ikeda
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Publication number: 20060061863Abstract: A low-cost compact optical attenuator having a simple structure is constructed from an input port and an output port for optical signals arranged side by side; a reflecting member arranged to face both of the ports to reverse light from the input side on an optical path folded 180°; a birefringence crystal which splits incident light into two polarization components, a converging lens which converges the incident light, a fixed Faraday rotator having a fixed rotation angle, and a variable Faraday rotator having a variable rotation angle arranged in that order in the optical path; wherein the reflecting member is a partial reflecting member that transmits a portion of the incident light to the rear side thereof, an optical sensor is provided at the rear side of the reflecting member, optical guide means are provided to guide only the transmitted light from the input port side to the optical sensor, and optical detection signals of the optical sensor are used as optical input monitoring signals.Type: ApplicationFiled: September 17, 2004Publication date: March 23, 2006Applicant: FDK CORPORATIONInventors: Hidenori Nakada, Shusuke Wada, Keisuke Ikeda, Yuko Ota
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Patent number: 7006273Abstract: Optical devices including a Faraday rotation devices improved in wavelength and temperature characteristics and an optical attenuator reduced in wavelength dependence and temperature-dependent loss. The Faraday rotation device has permanent magnets magnetized in an axial direction of through-holes, and Faraday elements having a same Faraday rotation direction with respect to a same magnetization direction. The permanent magnets are directed in the same magnetization direction along an optical path, where part of the Faraday elements are accommodated in the through-hole of the permanent magnet, and the remaining Faraday elements are arranged between the magnets, whereby the Faraday elements are to be applied by magnetic fields in opposite directions. For a device variable in Faraday rotation angle, an electromagnet is provided. An input fiber collimator and polarizer are provided on an input side of with the Faraday elements while an analyzer and output fiber collimator are on an output side.Type: GrantFiled: December 17, 2004Date of Patent: February 28, 2006Assignee: FDK CorporationInventors: Teruhisa Sahashi, Hidenori Nakada, Hirotaka Kawai, Isao Kojima, Tsugio Tokumasu
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Publication number: 20050141075Abstract: Optical devices including a Faraday rotation devices improved in wavelength and temperature characteristics and an optical attenuator reduced in wavelength dependence and temperature-dependent loss. The Faraday rotation device has permanent magnets magnetized in an axial direction of through-holes, and Faraday elements having a same Faraday rotation direction with respect to a same magnetization direction. The permanent magnets are directed in the same magnetization direction along an optical path, where part of the Faraday elements are accommodated in the through-hole of the permanent magnet, and the remaining Faraday elements are arranged between the magnets, whereby the Faraday elements are to be applied by magnetic fields in opposite directions. For a device variable in Faraday rotation angle, an electromagnet is provided. An input fiber collimator and polarizer are provided on an input side of with the Faraday elements while an analyzer and output fiber collimator are on an output side.Type: ApplicationFiled: December 17, 2004Publication date: June 30, 2005Inventors: Teruhisa Sahashi, Hidenori Nakada, Hirotaka Kawai, Isao Kojima, Tsugio Tokumasu
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Publication number: 20050134954Abstract: A variable optical filter comprises a first polarizer, a first phase difference element operable to generate a phase difference, a variable Faraday rotator operable to impart a variable Faraday rotation, a second phase difference element operable to generate a phase difference, and a second polarizer, wherein said polarizers, said variable Faraday rotator, and said phase difference elements are arranged in the mentioned order along the optical axis, and wherein when the angles formed by the optic axes of said first and second phase difference elements and the transmitted polarization azimuth of the first polarizer are assumed respectively to be ?1 and ?2, these ?1 and ?2 are set to different angles.Type: ApplicationFiled: December 10, 2004Publication date: June 23, 2005Applicants: FIJITSU LIMITED, FDK CORPORATIONInventors: Nobuhiro Fukushima, Hidenori Nakada, Tsugio Tokumasu, Yuko Ota
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Patent number: 6876480Abstract: Optical devices including a Faraday rotation devices improved in wavelength and temperature characteristics and an optical attenuator reduced in wavelength dependence and temperature-dependent loss. The Faraday rotation device has permanent magnets magnetized in an axial direction of through-holes, and Faraday elements having a same Faraday rotation direction with respect to a same magnetization direction. The permanent magnets are directed in the same magnetization direction along an optical path, where part of the Faraday elements are accommodated in the through-hole of the permanent magnet, and the remaining Faraday elements are arranged between the magnets, whereby the Faraday elements are to be applied by magnetic fields in opposite directions. For a device variable in Faraday rotation angle, an electromagnet is provided. An input fiber collimator and polarizer are provided on an input side of with the Faraday elements while an analyzer and output fiber collimator are on an output side.Type: GrantFiled: July 25, 2001Date of Patent: April 5, 2005Assignee: FDK CorporationInventors: Teruhisa Sahashi, Hidenori Nakada, Hirotaka Kawai, Isao Kojima, Tsugio Tokumasu
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Publication number: 20040234227Abstract: A reflection-type variable optical attenuator comprises: a main attenuator unit including a first birefringent crystal plate, a Faraday rotational angle varying unit, and a second birefringent crystal plate arranged in this order; an input port and an output port that are arranged on a side of one end of the main attenuator unit; and a two-point reflection-type optical path varying reflector that is arranged on a side of the other end of the main attenuator unit. Light that comes in from the input port makes a round trip in the main attenuator unit and goes out through the output port.Type: ApplicationFiled: June 23, 2004Publication date: November 25, 2004Inventors: Teruhisa Sahashi, Hidenori Nakada, Shohei Abe, Isao Kojima, Keisuke Ikeda
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Patent number: 6798566Abstract: A variable optical gain equalizer in accordance with one embodiment of the present invention comprises a variable branching ratio beam splitter having a variable polarization rotator, the variable branching ratio beam splitter branching an input light beam into two light beams at an arbitrary power ratio, through control of the rotation angle of the polarization direction by the variable polarization rotator; an optical filter presenting different filter characteristics to the two branched output light beams; and a polarization coupler for polarization coupling the two light beams that have passed through the optical filter, wherein the rotation angle of the polarization direction is controlled by the variable polarization rotator so as to vary the spectra of the output light beams.Type: GrantFiled: June 13, 2002Date of Patent: September 28, 2004Assignee: FDK CorporationInventors: Shohei Abe, Hidenori Nakada, Mototsugu Goto, Ikuo Maeda, Hideo Takeshita, Hiroaki Ono, Shusuke Wada
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Publication number: 20040027637Abstract: Various optical devices are provided including a Faraday rotation devices improved in wavelength and temperature characteristics and an optical attenuator reduced in wavelength dependence and temperature-dependent loss. The present invention is a Faraday rotation device 22 having permanent magnets 24, 30 magnetized in an axial direction of through-holes and Faraday elements 28, 32 having a same Faraday rotation direction with respect to a same magnetization direction, the permanent magnets being arranged directed in the same magnetization direction along an optical path, part of the Faraday elements being accommodated in the through-hole of the permanent magnet, the remaining Faraday elements being arranged between the plurality of permanent magnets, whereby the Faraday elements are to be applied by magnetic fields in opposite directions. In the case of a device variable in Faraday rotation angle, an electromagnet (variable magnetic field applying means) 36 is provided.Type: ApplicationFiled: February 6, 2003Publication date: February 12, 2004Inventors: Teruhisa Sahashi, Hidenori Nakada, HIrotaka Kawai, Isao Kojima, Tsugio Tokumasu
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Publication number: 20020191274Abstract: A variable optical gain equalizer in accordance with one embodiment of the present invention comprises a variable branching ratio beam splitter having a variable polarization rotator, the variable branching ratio beam splitter branching an input light beam into two light beams at an arbitrary power ratio, through control of the rotation angle of the polarization direction by the variable polarization rotator; an optical filter presenting different filter characteristics to the two branched output light beams; and a polarization coupler for polarization coupling the two light beams that have passed through the optical filter, wherein the rotation angle of the polarization direction is controlled by the variable polarization rotator so as to vary the spectra of the output light beams.Type: ApplicationFiled: June 13, 2002Publication date: December 19, 2002Inventors: Shohei Abe, Hidenori Nakada, Mototsugu Goto, Ikuo Maeda, Hideo Takeshita, Hiroaki Ono, Shusuke Wada
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Patent number: 6288827Abstract: Disclosed is a Faraday rotator capable of reducing the temperature dependence on a Faraday rotation angle, thereby enhancing the temperature characteristic, particularly, in a service environment in which the magnetization direction is variable, and an optical device using the Faraday rotator. The Faraday rotator includes a Faraday element which rotates the polarization plane of polarized light rays passing through the Faraday element when an external magnetic field is applied to the Faraday element.Type: GrantFiled: February 26, 1999Date of Patent: September 11, 2001Assignees: FDK Corporation, Fujitsu LimitedInventors: Hirotaka Kawai, Hiromitsu Umezawa, Hidenori Nakada, Nobuhiro Fukushima
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Patent number: 6108120Abstract: A Faraday rotation angle varying apparatus for controlling a Faraday rotation angle of a light beam passing through a garnet single crystal having a Faraday effect by applying external magnetic fields to the garnet single crystal in two or more of directions and varying a synthetic magnetic field synthesized from the external magnetic fields is disclosed. According to an aspect of the present invention, the garnet single crystal has the (111) plane polished and the light beam is allowed to pass through the garnet single crystal along the <111> direction of the garnet single crystal perpendicular to the (111) plane. A displacement path of a synthetic vector of the external magnetic fields is within a fan-shaped range (peripheral lines of the fan-shape inclusive) of a stereographic projection chart of the garnet single crystal with the (111) plane taken as the center of the chart.Type: GrantFiled: August 25, 1998Date of Patent: August 22, 2000Assignee: FDK CorporationInventors: Hirotaka Kawai, Hiromitsu Umezawa, Youichi Suzuki, Hidenori Nakada