Patents by Inventor Satoki Kawanishi

Satoki Kawanishi 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).

  • Patent number: 8014645
    Abstract: A 1.55 ?m band dispersion shifted optical fiber is provided which has a low loss and low dispersion slope. A core region “a” is heavily doped with GeO2 . A core region “b” is composed of pure SiO2 glass. A cladding section is arranged around the core region. The cladding section has a lot of holes extending in the longitudinal direction of the optical fiber. The holes of the cladding section are not located at random, but have a honeycomb structure composed of regular hexagons which have a side length of ?, and serve as a primitive lattice. The center of the core section has a region having a refractive index higher than that of the periphery of the core section. The core section has the refractive index distribution in which the group velocity dispersion at the operation wavelength of the region becomes the normal dispersion.
    Type: Grant
    Filed: May 16, 2003
    Date of Patent: September 6, 2011
    Assignees: Nippon Telegraph and Telephone Corporation, Mitsubishi Cable Industries, Ltd.
    Inventors: Kazunori Suzuki, Satoki Kawanishi, Hirokazu Kubota, Masatoshi Tanaka, Moriyuki Fujita
  • Publication number: 20100266250
    Abstract: A 1.55 ?m band dispersion shifted optical fiber is provided which has a low loss and low dispersion slope. A core region “a” is heavily doped with GeO2 . A core region “b” is composed of pure SiO2 glass. A cladding section is arranged around the core region. The cladding section has a lot of holes extending in the longitudinal direction of the optical fiber. The holes of the cladding section are not located at random, but have a honeycomb structure composed of regular hexagons which have a side length of ?, and serve as a primitive lattice. The center of the core section has a region having a refractive index higher than that of the periphery of the core section. The core section has the refractive index distribution in which the group velocity dispersion at the operation wavelength of the region becomes the normal dispersion.
    Type: Application
    Filed: May 16, 2003
    Publication date: October 21, 2010
    Inventors: Kazunori Suzuki, Satoki Kawanishi, Hirokazu Kubota, Masatoshi Tanaka, Moriyuki Fujita
  • Patent number: 7373086
    Abstract: With a single laser light source, the line width of a beat signal is set to a few tens of kHz or less without it fluctuating over time, and the frequency thereof is set as desired. CW light from a CW laser light source is input into an electroabsorption modulator to which a sine wave electrical signal is applied. A modulation sideband which is made up from line spectra at separations equal to the modulation frequency is generated from the electroabsorption modulator. An optical fiber for higher-order soliton compression broadens the optical spectrum width, and increases the number of line spectra. A tunable wavelength filtering device which is made up from optical fiber gratings and optical circulators chooses two of the line spectra, which are combined by an optical coupler with their beat signal being heterodyne wave detected by a photo-detector.
    Type: Grant
    Filed: May 28, 2003
    Date of Patent: May 13, 2008
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Takashi Yamamoto, Satoki Kawanishi
  • Patent number: 7151897
    Abstract: This optical clock phase-locked loop circuit includes an oscillator 12, an optical coupler 2, an optical cross-correlation detection device 3 that outputs light containing the correlating components of two lights from the coupled light of optical coupler 2, an optical band pass filter 4 that extracts light of a wavelength that contains cross-correlating components, an optical receiver 5, a phase comparator 6 that compares the phases of the output signal of the oscillator 12 and the cross-correlation signal from the optical receiver 5, a voltage controlled oscillator 7 that changes the oscillation frequency and phase corresponding to the output of the phase comparator 6, an optical pulse generator 8 that generates a optical clock pulse containing an nth harmonic component, an optical coupler 10 that divides optical clock, and an optical modulator 11 driven by low-frequency oscillator 12 that modulates optical clock from optical coupler 10.
    Type: Grant
    Filed: December 4, 2002
    Date of Patent: December 19, 2006
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Takuya Ohara, Hidehiko Takara, Satoki Kawanishi
  • Patent number: 7046887
    Abstract: A polarization-maintaining optical fiber and absolutely single-polarization optical fiber are provided which enable long distance transmission maintaining a polarization state of signal light. The polarization-maintaining optical fiber includes a core, photonic crystal cladding, and jacket. The photonic crystal cladding is divided into four segments by broken lines from the center to the periphery. Among a plurality of grating holes in a pair of segments opposed to each other with respect to the core, the diameter of grating holes close to the core is greater than the diameter of grating holes in another pair of segments opposed with each other, and than a grating constant.
    Type: Grant
    Filed: September 26, 2002
    Date of Patent: May 16, 2006
    Assignees: Nippon Telegraph and Telephone Corporation, Mitsubishi Cable Industries, Ltd.
    Inventors: Satoki Kawanishi, Kazunori Suzuki, Hirokazu Kubota, Masatoshi Tanaka, Moriyuki Fujita
  • Publication number: 20060024009
    Abstract: A single mode photonic crystal fiber including a core with a geometric radius ?, and a cladding surrounding the core, the cladding including a plurality of cylindrical air holes which have a diameter d and are arranged periodically at center-to-center spacings of ?. A design is made such that the center-to-center spacing ? between the air holes is made 1.5 or more times greater than a wavelength ? of propagation light, and a V value given by the following expression is made greater than 2.4 and less than 3.3. At least one of geometric placement of the air holes in the cladding and optical constant distribution of the cladding or core is set less than three-fold rotational symmetry with respect to a central axis of the core. V = 2 ? ?? ? ? ( n core 2 - n eff 2 ) 1 / 2 where neff is an effective refractive index of the cladding, and ncore is a refractive index of the core.
    Type: Application
    Filed: November 12, 2003
    Publication date: February 2, 2006
    Inventors: Hirokazu Kubota, Satoki Kawanishi, Kazumori Suzuki
  • Publication number: 20050084223
    Abstract: A polarization-maintaining photonic crystal fiber 10 includes six thin holes 4a and 4b adjacent to a core 1. Among these holes 4a and 4b, a pair of holes 4b at opposite sides of the core 1 have a diameter greater than that of the other four thin holes 4a, and therefore, the polarization-maintaining photonic crystal fiber 10 has polarization-maintaining ability. An overclad layer 3 exists around the clad layer 2 which includes a large number of thin holes 4a and 4b around the core 1. The overclad layer 3 includes a pair of marking portions 5 at opposite sides of the core 1. The marking portions 5 are holes which can be seen at positions different from the clad layer 2 when the fiber 10 is viewed from a position right above the fiber 10 in the drawing. In this way, the direction of the polarization plane of the polarization-maintaining photonic crystal fiber 10 is identified.
    Type: Application
    Filed: January 23, 2003
    Publication date: April 21, 2005
    Inventors: Masatoshi Tanaka, Shinya Yamadori, Moriyuki Fujita, Satoki Kawanishi, Kazunori Suzuki, Hirokazu Kubota
  • Publication number: 20050025441
    Abstract: A polarization-maintaining optical fiber and absolutely single-polarization optical fiber are provided which enable long distance transmission maintaining a polarization state of signal light. The polarization-maintaining optical fiber includes a core, photonic crystal cladding, and jacket. The photonic crystal cladding is divided into four segments by broken lines from the center to the periphery. Among a plurality of grating holes in a pair of segments opposed to each other with respect to the core, the diameter of grating holes close to the core is greater than the diameter of grating holes in another pair of segments opposed with each other, and than a grating constant.
    Type: Application
    Filed: September 26, 2002
    Publication date: February 3, 2005
    Inventors: Satoki Kawanishi, Kazunori Suzuki, Hirokazu Kubota, Masotoshi Tanaka, Moriyuki Fujita
  • Patent number: 6842565
    Abstract: An optical modulation/multiplexing circuit can fabricate a plurality of nonlinear optical waveguide devices and silica optical waveguides through a small number of processes, and achieve the simplification of the fabrication process and stabilization of the operation by hybrid integration with reduced connection loss. It employs lithium niobate domain inversion optical waveguides as nonlinear optical switches, and implements functions necessary for modulation and multiplexing such as input, splitting, multiplexing and timing adjustment of optical modulation signals and an optical clock signal by connecting glass waveguides to the input and output terminals of the domain inversion optical waveguides. Nonlinear optical media generate a second harmonic light beam of the optical clock signal, and at the same time produces a light beam with a frequency corresponding to the difference frequency of the two high frequency signals, the second harmonic light beam and the signal pulses.
    Type: Grant
    Filed: May 14, 2003
    Date of Patent: January 11, 2005
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Takuya Ohara, Hidehiko Takara, Ippei Shake, Satoki Kawanishi
  • Patent number: 6788865
    Abstract: A polarization maintaining optical fiber is formed by using a core in a cross sectional shape having different diameters along two orthogonal axes defined on a plane perpendicular to an optical axis, or a photonic crystal structure cladding having a diffraction grating with lattice intervals for realizing confinement of lights within the core which are different along two orthogonal axes defined on a plane perpendicular to an optical axis, or the photonic crystal structure cladding that is divided into four divided portions along a circumferential direction, where at least a part of lattice holes in a first pair of divided portions that are facing each other along one direction have a diameter larger than that of lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction.
    Type: Grant
    Filed: March 5, 2001
    Date of Patent: September 7, 2004
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Satoki Kawanishi, Katsunari Okamoto
  • Patent number: 6720548
    Abstract: A nonlinear optical crystal is composed of 2-adamantyl-5-nitorpyridine (AANP) allowing the type 2 phase matching to the sampling light and a measuring object light, emitting a sum frequency light of the measuring object light and the sampling light, with the polarization directions thereof being perpendicular to each other, when the sampling light and measuring object light multiplexed by a multiplexer are entered. When the sum frequency light is emitted through the nonlinear optical crystal, a control portion controls the polarization direction of the sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of the nonlinear optical crystal. The predetermined reference axis is a single axis maintaining parallelism with the crystal axis of the nonlinear optical crystal even if the wavelength of the inputted light is changed.
    Type: Grant
    Filed: March 12, 2002
    Date of Patent: April 13, 2004
    Assignees: Anritsu Corporation, Nippon Telegraph & Telephone Corporation
    Inventors: Akihito Otani, Toshinobu Otsubo, Hidehiko Takara, Ippei Shake, Satoki Kawanishi
  • Patent number: 6697395
    Abstract: A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency &ohgr;D and a variable wavelength light having an angular frequency &ohgr;S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency &ohgr;D+&ohgr;S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.
    Type: Grant
    Filed: March 12, 2002
    Date of Patent: February 24, 2004
    Assignees: Anritsu Corporation, Nippon Telegraph & Telephone Corporation
    Inventors: Akihito Otani, Toshinobu Otsubo, Hidehiko Takara, Ippei Shake, Satoki Kawanishi
  • Publication number: 20040028089
    Abstract: Signal channels are identified easily by uniquely correlating the port numbers of the optical time-division-demultiplexing unit with channel numbers. The extraction apparatus includes an optical time-division-demultiplexing unit that separates multiplexed signals into N channels and provides them to N separate ports, a channel extraction unit that is connected to N separate ports and extracts one channel number of the N channels, a channel switch that switches the N channels to the output ports of which port numbers uniquely match with the numbers of the N channels based on the relationship between the number of the one channel extracted and the output port number corresponding to the one channel number, and a data output unit that has N output ports and provides the signals of the switched N channels to the output ports of which port numbers match with the channel numbers.
    Type: Application
    Filed: July 21, 2003
    Publication date: February 12, 2004
    Applicant: Nippon Telegraph and Telephone Corporation
    Inventors: Ippei Shake, Hidehiko Takara, Satoki Kawanishi
  • Patent number: 6671444
    Abstract: An optical fiber, capable of generating by means of nonlinear phenomena, white light in adequately broadened wavelength bands at both sides of a pumping optical pulse that is input, and stabilizing the polarized conditions. The fiber is formed by covering a core with a first cladding, and covering the first cladding with a second cladding, where the second cladding has a refractive index greater than that of the first cladding, but lower than that of the core. Stress-applying parts are provided inside the second cladding so as to sandwich the core from both sides to form a polarization-maintaining optical fiber. The shortest distance between the stress-applying parts is made 2.3 times or more the mode field diameter for the wavelength of the pumping optical pulse.
    Type: Grant
    Filed: May 21, 2001
    Date of Patent: December 30, 2003
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Shinichi Arai, Takeshi Yagi, Kunihiko Mori, Hidehiko Takara, Satoki Kawanishi
  • Publication number: 20030223757
    Abstract: With a single laser light source, the line width of a beat signal is set to a few tens of kHz or less without it fluctuating over time, and the frequency thereof is set as desired. CW light from a CW laser light source is input into an electroabsorption modulator to which a sine wave electrical signal is applied. A modulation sideband which is made up from line spectra at separations equal to the modulation frequency is generated from the electroabsorption modulator. An optical fiber for higher-order soliton compression broadens the optical spectrum width, and increases the number of line spectra. A tunable wavelength filtering device which is made up from optical fiber gratings and optical circulators chooses two of the line spectra, which are combined by an optical coupler with their beat signal being heterodyne wave detected by a photo-detector.
    Type: Application
    Filed: May 28, 2003
    Publication date: December 4, 2003
    Inventors: Takashi Yamamoto, Satoki Kawanishi
  • Publication number: 20030214698
    Abstract: An optical modulation/multiplexing circuit can fabricate a plurality of nonlinear optical waveguide devices and silica optical waveguides through a small number of processes, and achieve the simplification of the fabrication process and stabilization of the operation by hybrid integration with reduced connection loss. It employs lithium niobate domain inversion optical waveguides as nonlinear optical switches, and implements functions necessary for modulation and multiplexing such as input, splitting, multiplexing and timing adjustment of optical modulation signals and an optical clock signal by connecting glass waveguides to the input and output terminals of the domain inversion optical waveguides. Nonlinear optical media generate a second harmonic light beam of the optical clock signal, and at the same time produces a light beam with a frequency corresponding to the difference frequency of the two high frequency signals, the second harmonic light beam and the signal pulses.
    Type: Application
    Filed: May 14, 2003
    Publication date: November 20, 2003
    Applicant: Nippon Telegraph and Telephone Corporation
    Inventors: Takuya Ohara, Hidehiko Takara, Ippei Shake, Satoki Kawanishi
  • Publication number: 20030118349
    Abstract: This optical clock phase-locked loop circuit includes an oscillator 12, an optical coupler 2, an optical cross-correlation detection device 3 that outputs light containing the correlating components of two lights from the coupled light of optical coupler 2, an optical band pass filter 4 that extracts light of a wavelength that contains cross-correlating components, an optical receiver 5, a phase comparator 6 that compares the phases of the output signal of the oscillator 12 and the cross-correlation signal from the optical receiver 5, a voltage controlled oscillator 7 that changes the oscillation frequency and phase corresponding to the output of the phase comparator 6, an optical pulse generator 8 that generates a optical clock pulse containing an nth harmonic component, an optical coupler 10 that divides optical clock, and an optical modulator 11 driven by low-frequency oscillator 12 that modulates optical clock from optical coupler 10.
    Type: Application
    Filed: December 4, 2002
    Publication date: June 26, 2003
    Inventors: Takuya Ohara, Hidehiko Takara, Satoki Kawanishi
  • Publication number: 20030056550
    Abstract: The present invention provides a method for manufacturing a photonic crystal fiber that has a core portion in which a fiber core extends in a lengthwise direction and is formed as a solid or a void, and a porous clad portion provided around the core portion and having numerous pores extending along the core portion. A preform is fabricated by packing numerous capillaries into a cylindrical support pipe such that they are parallel to the central axis of the support pipe and disposing a core rod to serve as the solid core portion at the central axis portion of the support pipe. The preform is drawn to make it small in diameter.
    Type: Application
    Filed: May 22, 2002
    Publication date: March 27, 2003
    Inventors: Masatoshi Tanaka, Tetsuya Yamamoto, Shigeki Koyanagi, Minoru Yoshida, Moriyuki Fujita, Masataka Nakazawa, Hirokazu Kubota, Satoki Kawanishi
  • Publication number: 20020139924
    Abstract: A nonlinear optical crystal is composed of 2-adamantyl-5-nitorpyridine (AANP) allowing the type 2 phase matching to the sampling light and a measuring object light, emitting a sum frequency light of the measuring object light and the sampling light, with the polarization directions thereof being perpendicular to each other, when the sampling light and measuring object light multiplexed by a multiplexer are entered. When the sum frequency light is emitted through the nonlinear optical crystal, a control portion controls the polarization direction of the sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of the nonlinear optical crystal. The predetermined reference axis is a single axis maintaining parallelism with the crystal axis of the nonlinear optical crystal even if the wavelength of the inputted light is changed.
    Type: Application
    Filed: March 12, 2002
    Publication date: October 3, 2002
    Applicant: Anritsu Corporation
    Inventors: Akihito Otani, Toshinobu Otsubo, Hidehiko Takara, Ippei Shake, Satoki Kawanishi
  • Publication number: 20020141459
    Abstract: A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency &ohgr;D and a variable wavelength light having an angular frequency &ohgr;S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency &ohgr;D+&ohgr;S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.
    Type: Application
    Filed: March 12, 2002
    Publication date: October 3, 2002
    Applicant: Anritsu Corporation
    Inventors: Akihito Otani, Toshinobu Otsubo, Hidehiko Takara, Ippei Shake, Satoki Kawanishi