Patents by Inventor Kazutaka Nara

Kazutaka Nara 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: 7539368
    Abstract: An arrayed waveguide grating has optical input waveguides, a first slab waveguide, an arrayed waveguide comprising plural waveguides of mutually-different lengths, a second slab waveguide and plural optical output waveguides. The first slab waveguide is divided along division surfaces crossing the light path into divided slab waveguides. The divided slab waveguide is temperature-dependently moved along the division surfaces by sliding members which are formed of members exhibiting different expansion/contraction corresponding to temperature change. The sliding members are configured to move the divided slab waveguide in their respective mutually-different temperature ranges in the operating temperature range of the arrayed waveguide grating. A sliding distance of the divided slab waveguide is used as a temperature-dependence reduction amount that varies as temperature changes so as to reduce the temperature difference of the light transmission center wavelength of the arrayed waveguide grating.
    Type: Grant
    Filed: March 3, 2008
    Date of Patent: May 26, 2009
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Junichi Hasegawa, Kazutaka Nara
  • Publication number: 20090110393
    Abstract: Two Mach-Zehnder optical interferometer circuits 13a and 13b are accurately point-symmetrically connected to each other to form a first point-symmetrically connected optical interferometer circuit 5 constituting a light input side circuit 1. Optical signals having a plurality of wavelengths are input to a light input terminal 17. A second point-symmetrically connected optical interferometer circuit 7 having the same functional structure as the first point-symmetrically connected optical interferometer circuit 5 is connected to a through port 18, which is an output terminal of the light input side circuit 1, as a first light output side circuit 2. A cross port 19, which is the other output terminal of the light input side circuit 1, is connected to a second light output side circuit 3 having at least one of Mach-Zehnder optical interferometer circuits 13c and 13d whose transmittance characteristics are different from those of the Mach-Zehnder optical interferometer circuits 13a and 13b.
    Type: Application
    Filed: November 26, 2008
    Publication date: April 30, 2009
    Applicant: The FURUKAWA ELECTRIC CO., LTD.
    Inventors: Kazutaka NARA, Haruki Urabe, Tsunetoshi Saitoh, Masahito Morimoto
  • Publication number: 20090097101
    Abstract: Problem to be Solved To provide a delay-line demodulator of which the divergence amount of polarization is reduced. Solution: A delay-line demodulator 1 for a DQPSK signal to be demodulated comprises two of Mach-Zehnder interferometers 6 and 7 individually comprising two of waveguides having different lengths therebetween through which a light signal branched the DQPSK signal propagates respectively, for delaying a phase of the light signal propagating at one of the waveguides as an amount of one symbol comparing to a phase of the light signal propagating at another one of the waveguides, wherein a divergence amount of polarization is adjusted by driving a first heater A and a fourth heater D, or a third heater B and a second heater C, that are facing to each other as sandwiching a half wavelength plate therebetween.
    Type: Application
    Filed: October 9, 2008
    Publication date: April 16, 2009
    Applicant: FURUKAWA ELECTRIC CO., LTD
    Inventors: Junichi Hasegawa, Kazutaka Nara
  • Patent number: 7492983
    Abstract: The present invention provide an optical circuit device having: an optical circuit; a polarization beam splitter/combiner for splitting an incoming light beam into two polarization beams and combining the two polarization beams into an outgoing light beam; a first optical waveguide and a second optical waveguide for connecting the optical circuit and the polarization beam splitter/combiner and receiving the two polarization beams independently; and a polarization rotator, arranged on the first optical waveguide, for rotating a polarization plane of one of the two polarization beams split by the polarization beam splitter/combiner so as to match a polarization plane of the other of the two polarization beams, the optical circuit, the polarization beam splitter/combiner, the first optical waveguide, the second optical waveguide and the polarization rotator being integrated on a planar substrate.
    Type: Grant
    Filed: August 4, 2005
    Date of Patent: February 17, 2009
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Noritaka Matsubara, Hiroshi Kawashima, Kazutaka Nara
  • Patent number: 7480091
    Abstract: In a method of phase adjustment for the demodulator 1 of the present invention, the phase adjustment is performed by driving any one of the heaters on the two waveguides 10 and 11 in the Mach-Zehnder interferometer (MZI) 6 and on the two waveguides 14 and 15 in the MZI 7. In case that an initial phase difference between the MZIs 6 and 7 smaller than a required phase difference as ?/2 therebetween, the heaters C and D are driven, that are formed on the first waveguide 10 in the MZI 6, and the heaters G and H are driven, that are formed on the second waveguide 15 in the MZI 7. In case that the initial phase difference is larger than the required phase difference (?/2) therebetween, the heaters A and B formed on the second waveguide 11 in the MZI 6, and the heaters E and F formed on the first waveguide 14 in the MZI 7 are driven.
    Type: Grant
    Filed: March 5, 2008
    Date of Patent: January 20, 2009
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Junichi Hasegawa, Kazutaka Nara
  • Patent number: 7469079
    Abstract: Two Mach-Zehnder optical interferometer circuits 13a and 13b are accurately point-symmetrically connected to each other to form a first point-symmetrically connected optical interferometer circuit 5 constituting a light input side circuit 1. Optical signals having a plurality of wavelengths are input to a light input terminal 17. A second point-symmetrically connected optical interferometer circuit 7 having the same functional structure as the first point-symmetrically connected optical interferometer circuit 5 is connected to a through port 18, which is an output terminal of the light input side circuit 1, as a first light output side circuit 2. A cross port 19, which is the other output terminal of the light input side circuit 1, is connected to a second light output side circuit 3 having at least one of Mach-Zehnder optical interferometer circuits 13c and 13d whose transmittance characteristics are different from those of the Mach-Zehnder optical interferometer circuits 13a and 13b.
    Type: Grant
    Filed: January 25, 2005
    Date of Patent: December 23, 2008
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Kazutaka Nara, Haruki Urabe, Tsunetoshi Saitoh, Masahito Morimoto
  • Publication number: 20080253716
    Abstract: An arrayed waveguide grating optical multiplexer/demultiplexer 1 comprises an arrayed waveguide grating 20 formed on a substrate 10. The arrayed waveguide grating 20 comprises two slab waveguides 21, 22, one arrayed waveguide 23, first input/output waveguides A, B respectively connected to each end facet 21a, 22a of slab waveguides 21, 22, and second input/output waveguide-groups C, D respectively connected to the end facets 21a, 22a. The first input/output waveguides A, B are provided for inputting or outputting a plurality of lights (?1˜?n) each of which has a different wavelength and multiplexed. The second input/output waveguides C, D are provided for individually inputting or outputting a plurality of lights (?1˜?n). One arrayed waveguide 23 can be used to carry out simultaneously multiplexing and demultiplexing. It is able to carry out simultaneously multiplexing and demultiplexing with one arrayed waveguide grating 20.
    Type: Application
    Filed: March 27, 2008
    Publication date: October 16, 2008
    Applicant: The Furukawa Electric Co, Ltd.
    Inventor: Kazutaka Nara
  • Publication number: 20080239465
    Abstract: In a method of phase adjustment for the demodulator 1 of the present invention, the phase adjustment is performed by driving any one of the heaters on the two waveguides 10 and 11 in the Mach-Zehnder interferometer (MZI) 6 and on the two waveguides 14 and 15 in the MZI 7. In case that an initial phase difference between the MZIs 6 and 7 smaller than a required phase difference as ?/2 therebetween, the heaters C and D are driven, that are formed on the first waveguide 10 in the MZI 6, and the heaters G and H are driven, that are formed on the second waveguide 15 in the MZI 7. In case that the initial phase difference is larger than the required phase difference (?/2) therebetween, the heaters A and B formed on the second waveguide 11 in the MZI 6, and the heaters E and F formed on the first waveguide 14 in the MZI 7 are driven.
    Type: Application
    Filed: March 5, 2008
    Publication date: October 2, 2008
    Applicant: The Furukawa Electric Co., Ltd.
    Inventors: Junichi Hasegawa, Kazutaka Nara
  • Publication number: 20080240645
    Abstract: An optical integrated circuit 1 according to the present invention includes a planar lightwave circuit 2, and a semiconductor element 3, which are fixed at one contact surface 12. A semiconductor optical amplifier (SOA) 9 is formed on a semiconductor substrate 8. A semiconductor waveguide 10 and a semiconductor waveguide 11 are formed on an input side and an output side of SOA 9, respectively. The semiconductor waveguide 11 has a turnaround portion 11a turned around on the semiconductor substrate 8. Respective ends of the optical waveguides 5 and 6 on a PLC platform 4 and respective ends of semiconductor waveguides 10 and 11 are optically coupled with each other at the contact surface 12.
    Type: Application
    Filed: March 10, 2008
    Publication date: October 2, 2008
    Applicant: THE FURUKAWA ELECTRIC CO., LTD.
    Inventors: Masaki FUNABASHI, Junichi Hasegawa, Takeshi Akutsu, Kazutaka Nara, Noriyuki Yokouchi
  • Publication number: 20080240727
    Abstract: The tunable dispersion compensator 10 of the present invention comprises: the Mach-Zehnder interferometers (MZIs) 21 to 25 cascaded on a planar lightwave circuit; and the tunable couplers 31 to 34 connected to between each corresponding pair of the MZIs respectively. The Y-branch waveguide 15 and 16 are used for connecting to between the MZIs 21, 25 as both end sides and the input/output optical waveguides 13, 14 respectively. The waveguide loop mirror 40 is connected to the final stage MZI 25 among the MZIs 21 to 25 which an incident light is propagated last therethrough. The half-wave plate 50 is inserted to the loop waveguide 41 of the waveguide loop mirror 40. And it becomes able to enhance (double) the amount of tunable dispersion because an input light signal is passed twice through the similar path by the waveguide loop mirror 40.
    Type: Application
    Filed: March 5, 2008
    Publication date: October 2, 2008
    Applicant: The Furukawa Electric Co., Ltd.
    Inventors: Hiroshi Kawashima, Kazutaka Nara
  • Publication number: 20080199130
    Abstract: The present invention enables reduction of the temperature dependence of the light transmission center wavelength of the arrayed waveguide grating. Provided is an arrayed waveguide grating having optical input waveguides 2, a first slab waveguide 3, an arrayed waveguide comprising plural waveguides of mutually-different lengths, a second slab waveguide 5 and plural optical output waveguides 6. The first slab waveguide 3 is divided along division surfaces 8 crossing the light path into divided slab waveguides 3a and 3b. The divided slab waveguide 3a is temperature-dependently moved along the division surfaces by sliding members 7a, 7b and 7c which are formed of members exhibiting different expansion/contraction corresponding to temperature change. The sliding members 7a, 7b and 7c are configured to move the divided slab waveguide 3a in their respective mutually-different temperature ranges in the operating temperature range of the arrayed waveguide grating.
    Type: Application
    Filed: March 3, 2008
    Publication date: August 21, 2008
    Applicant: The Furukawa Electric Co, Ltd.
    Inventors: Junichi Hasegawa, Kazutaka Nara
  • Publication number: 20080131053
    Abstract: An arrayed waveguide grating optical multiplexer/demultiplexer 10 of the present invention 10 comprises one arrayed waveguide grating (AWG) 20 having two input waveguides 21, 22 and two output waveguide-groups 23, 24, and a Mach Zehnder Interferometer-type interleaver 30 integrated with the AWG 20. Each of the input waveguides 21, 22 is formed by a Mach Zehnder Interferometer having the same free spectral range as the frequency spacing of the AWG. The Interferometer includes a 3 dB coupler 51 connected to the 3 dB coupler 32, a 100% coupler 52, a waveguide delay line 53 with an optical path length difference ?L of 4.1 mm formed between the couplers 51, 52, and a phase shifter 54 of ? formed between the 100% coupler 52 and a 3 dB coupler 55 connected to the first slab waveguide 25.
    Type: Application
    Filed: August 24, 2007
    Publication date: June 5, 2008
    Applicant: THE FURUKAWA ELECTRIC CO., LTD.
    Inventor: Kazutaka NARA
  • Publication number: 20080031566
    Abstract: The present invention provide an optical circuit device having: an optical circuit; a polarization beam splitter/combiner for splitting an incoming light beam into two polarization beams and combining the two polarization beams into an outgoing light beam; a first optical waveguide and a second optical waveguide for connecting the optical circuit and the polarization beam splitter/combiner and receiving the two polarization beams independently; and a polarization rotator, arranged on the first optical waveguide, for rotating a polarization plane of one of the two polarization beams split by the polarization beam splitter/combiner so as to match a polarization plane of the other of the two polarization beams, the optical circuit, the polarization beam splitter/combiner, the first optical waveguide, the second optical waveguide and the polarization rotator being integrated on a planar substrate.
    Type: Application
    Filed: August 4, 2005
    Publication date: February 7, 2008
    Applicant: The Furukawa Electric Co., Ltd
    Inventors: Noritaka Matsubara, Hiroshi Kawashima, Kazutaka Nara
  • Patent number: 7233714
    Abstract: Provided is a planar optical waveguide circuit type variable attenuator capable of light attenuation by an arbitrary value in a range from 0 to 10 dB and also by not less than 30 dB, which is small-sized and is of power saving type. The attenuator is composed of a Mach-Zehnder interferometer circuit 30 having input waveguides 1a, 1b and an output waveguide 1d which are formed on an optical waveguide layer 3, and comprises a slit 12 formed on the waveguide layer in a longitudinally intermediate part of at least one of the optical waveguides 1a, 1b, 1d and in a direction crossing the optical waveguides 1a, 1b, 1d, and matching medium displacing means 16a, 16b for displacing index-matching medium 13 in a part of the slit 12 from a position including a path of propagation light in the optical waveguides 1a, 1b, 1d, and a position retracted from the path of propagation light.
    Type: Grant
    Filed: February 13, 2006
    Date of Patent: June 19, 2007
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Hiroshi Kawashima, Kazutaka Nara
  • Publication number: 20070104409
    Abstract: Two Mach-Zehnder optical interferometer circuits 13a and 13b are accurately point-symmetrically connected to each other to form a first point-symmetrically connected optical interferometer circuit 5 constituting a light input side circuit 1. Optical signals having a plurality of wavelengths are input to a light input terminal 17. A second point-symmetrically connected optical interferometer circuit 7 having the same functional structure as the first point-symmetrically connected optical interferometer circuit 5 is connected to a through port 18, which is an output terminal of the light input side circuit 1, as a first light output side circuit 2. A cross port 19, which is the other output terminal of the light input side circuit 1, is connected to a second light output side circuit 3 having at least one of Mach-Zehnder optical interferometer circuits 13c and 13d whose transmittance characteristics are different from those of the Mach-Zehnder optical interferometer circuits 13a and 13b.
    Type: Application
    Filed: January 25, 2005
    Publication date: May 10, 2007
    Applicant: THE FURUKAWA ELECTRIC CO., LTD.
    Inventors: Kazutaka Nara, Haruki Urabe, Tsunetoshi Saitoh, Masahito Morimoto
  • Patent number: 7146079
    Abstract: The dynamic gain equalizer for flattening a gain profile of an optical amplifier includes: an optical waveguide circuit having multistage optical couplers, demultiplexing and multiplexing, each formed by connecting optical couplers arranged at a plurality of stages; and optical connecting circuits including optical phase shifters each capable of changing a phase of propagating light and optical delay lines each for adding a predetermined delay time to the propagating light, said dynamic gain equalizer in which at least one of the optical couplers in the two multistage optical couplers are provided with variable optical amplitude means, respectively, and each of the multistage optical couplers are formed asymmetrically with respect to an extension of a line which connects a center arranged position of optical outputting ends of the demultiplexing multistage optical coupler with a center arranged position of optical inputting ends of the multiplexing multistage optical coupler.
    Type: Grant
    Filed: April 25, 2005
    Date of Patent: December 5, 2006
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Kazutaka Nara, Kazuhisa Kashihara, Noritaka Matsubara
  • Patent number: 7133587
    Abstract: A dispersion compensator includes at least one first optical waveguide, a first slab waveguide, an arrayed waveguide connected to the at least one first optical waveguide via the first slab waveguide, a second slab waveguide, at least one second optical waveguide connected to the arrayed waveguide via the second slab waveguide, and a phase distribution provider configured to provide a phase distribution to the arrayed waveguide.
    Type: Grant
    Filed: May 3, 2006
    Date of Patent: November 7, 2006
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Kazutaka Nara, Kazuhisa Kashihara
  • Publication number: 20060204201
    Abstract: Provided is a planar optical waveguide circuit type variable attenuator capable of light attenuation by an arbitrary value in a range from 0 to 10 dB and also by not less than 30 dB, which is small-sized and is of power saving type. The attenuator is composed of a Mach-Zehnder interferometer circuit 30 having input waveguides 1a, 1b and an output waveguide 1d which are formed on an optical waveguide layer 3, and comprises a slit 12 formed on the waveguide layer in a longitudinally intermediate part of at least one of the optical waveguides 1a, 1b, 1d and in a direction crossing the optical waveguides 1a, 1b, 1d, and matching medium displacing means 16a, 16b for displacing index-matching medium 13 in a part of the slit 12 from a position including a path of propagation light in the optical waveguides 1a, 1b, 1d, and a position retracted from the path of propagation light.
    Type: Application
    Filed: February 13, 2006
    Publication date: September 14, 2006
    Applicant: THE FURUKAWA ELECTRIC CO., LTD.
    Inventors: Hiroshi Kawashima, Kazutaka Nara
  • Publication number: 20060193558
    Abstract: A dispersion compensator includes at least one first optical waveguide, a first slab waveguide, an arrayed waveguide connected to the at least one first optical waveguide via the first slab waveguide, a second slab waveguide, at least one second optical waveguide connected to the arrayed waveguide via the second slab waveguide, and a phase distribution provider configured to provide a phase distribution to the arrayed waveguide.
    Type: Application
    Filed: May 3, 2006
    Publication date: August 31, 2006
    Applicant: THE FURUKAWA ELECTRIC CO., LTD.
    Inventors: Kazutaka Nara, Kazuhisa Kashihara
  • Patent number: 7072545
    Abstract: A dispersion compensator includes at least one first optical waveguide, a first slab waveguide, an arrayed waveguide connected to the at least one first optical waveguide via the first slab waveguide, a second slab waveguide, at least one second optical waveguide connected to the arrayed waveguide via the second slab waveguide, and a phase distribution provider configured to provide a phase distribution to the arrayed waveguide.
    Type: Grant
    Filed: January 21, 2003
    Date of Patent: July 4, 2006
    Assignee: The Furukawa Electric Co., Ltd.
    Inventors: Kazutaka Nara, Kazuhisa Kashihara