Patents by Inventor Goji Nakagawa
Goji Nakagawa 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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Publication number: 20160294479Abstract: A communication device that receives received signal light from another communication device, the communication device includes: a receiver configured to receive signal light output from an optical filter that outputs signal light of a given wavelength included the received signal light; and a transmitter configured to transmit, to the another communication device, a control signal for controlling a wavelength of laser light for use in generation of the signal light of the given wavelength, wherein the receiver is configured to detect power of the signal light output from the optical filter; and the transmitter is configured to set, when the signal light is not successfully received in the receiver, the control signal so as to cause the another communication device to control the wavelength of the laser light, based on the power.Type: ApplicationFiled: March 25, 2016Publication date: October 6, 2016Applicant: FUJITSU LIMITEDInventors: Kyosuke Sone, Setsuo Yoshida, GOJI NAKAGAWA, Shoichiro Oda, Yasuhiko Aoki
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Publication number: 20160277139Abstract: An optical receiver receives a wavelength multiplexed optical signal including wavelength channels. A superimposition signal is superimposed by frequency modulation on each of the wavelength channels. The optical receiver includes: an optical filter that filters the wavelength multiplexed optical signal; a filter controller that controls a wavelength of a transmission band of the optical filter; a photo detector that generates an intensity signal representing a change in the intensity of an output light of the optical filter; an signal detector that detects, according to the intensity signal, a superimposition signal superimposed on a specified wavelength channel. The filter controller controls the wavelength of the transmission band so that the amplitude of the intensity signal is larger, and then controls the wavelength of the transmission band so that the number of errors in the superimposition signal detected by the signal detector is reduced.Type: ApplicationFiled: February 24, 2016Publication date: September 22, 2016Applicant: FUJITSU LIMITEDInventors: Setsuo Yoshida, GOJI NAKAGAWA, Tomohiro YAMAUCHI, Kyosuke Sone
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Patent number: 9444573Abstract: A transmission device that receives an optical signal on which a frequency modulated signal is superimposed includes: an optical filter configured to filter the optical signal; a filter controller configured to control a passband of the optical filter based on a change of power of the optical signal; and a signal detection unit configured to detect the frequency modulated signal based on the change of the power of the optical signal filtered by the optical filter.Type: GrantFiled: March 16, 2015Date of Patent: September 13, 2016Assignee: FUJITSU LIMITEDInventors: Goji Nakagawa, Shoichiro Oda
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Patent number: 9350479Abstract: A monitoring apparatus, that monitors a wavelength tunable optical filter for filtering an optical signal to which a frequency modulation component is added, includes: an optical filter configured to filter the optical signal output from the wavelength tunable optical filter; a detector configured to detect amplitude of the frequency modulation component included in the optical signal output from the optical filter; a generator configured to generate an output-side amplitude distribution representing a distribution of the amplitude of the frequency modulation component detected by the detector, by sweeping a transmission wavelength of the optical filter; and a monitoring unit configured to monitor arrangement of a transmission wavelength band of the wavelength tunable optical filter with respect to a spectrum of the optical signal based on the output-side amplitude distribution generated by the generator.Type: GrantFiled: December 4, 2013Date of Patent: May 24, 2016Assignee: FUJITSU LIMITEDInventors: Kyosuke Sone, Yasuhiko Aoki, Goji Nakagawa, Shoichiro Oda
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Publication number: 20150280852Abstract: A transmission device that receives an optical signal on which a frequency modulated signal is superimposed includes: an optical filter configured to filter the optical signal; a filter controller configured to control a passband of the optical filter based on a change of power of the optical signal; and a signal detection unit configured to detect the frequency modulated signal based on the change of the power of the optical signal filtered by the optical filter.Type: ApplicationFiled: March 16, 2015Publication date: October 1, 2015Inventors: GOJI NAKAGAWA, Shoichiro Oda
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Patent number: 9143242Abstract: An optical signal demodulator includes: an obtaining unit configured to obtain a spectrum of an optical signal generated by a second signal being superimposed on a first signal using frequency modulation; an identifying unit configured to identify a peak wavelength which is a wavelength corresponding to a peak position of the spectrum; and a demodulating unit configured to demodulate the second signal from the optical signal using a wavelength-variable filter to which a transmitted wavelength band has been set based on the peak wavelength.Type: GrantFiled: October 29, 2013Date of Patent: September 22, 2015Assignee: FUJITSU LIMITEDInventors: Goji Nakagawa, Kyosuke Sone, Shoichiro Oda, Yasuhiko Aoki
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Publication number: 20150155934Abstract: A device for monitoring optical signal includes: an optical filter configured to allow part of a spectrum of an optical signal on which a frequency or phase modulated signal is superimposed to pass; and a detection unit configured to detect signal quality of the optical signal, based on a power ratio of a signal component to a noise component of the modulated signal, the power ratio being obtained based on a power change in accordance with the modulated signal of light that has been caused to pass through the optical filter.Type: ApplicationFiled: November 10, 2014Publication date: June 4, 2015Applicant: FUJITSU LIMITEDInventors: Goji Nakagawa, Yasuhiko Aoki
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Patent number: 9019593Abstract: An optical amplification apparatus includes a front-stage semiconductor optical amplifier which amplifies an input light and a rear-stage semiconductor optical amplifier which amplifies an amplified light outputted from the front-stage semiconductor optical amplifier. The front-stage semiconductor optical amplifier exercises auto level control of an output light by exercising variable control of driving current which flows according to applied voltage higher than light emitting threshold voltage of an internal optical amplification element. The rear-stage semiconductor optical amplifier performs gate switching of a transmitted light by exercising switching control of driving current. By doing so, distortion of a waveform is controlled and optical communication quality can be improved.Type: GrantFiled: March 12, 2012Date of Patent: April 28, 2015Assignee: Fujitsu LimitedInventors: Setsuo Yoshida, Susumu Kinoshita, George Ishikawa, Goji Nakagawa, Yutaka Kai, Kyosuke Sone, Keisuke Harada
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Patent number: 8942567Abstract: An optical receiving device includes multiple input ports to which light is input; multiple amplifiers that are arrayed and provided corresponding to the input ports, respectively, each of the amplifiers amplifying and outputting light input from a corresponding input port among of the input ports; a photo diode that converts light into an electrical signal; and a lens that inputs to the photo diode light output from the amplifiers.Type: GrantFiled: December 13, 2011Date of Patent: January 27, 2015Assignee: Fujitsu LimitedInventors: Goji Nakagawa, Susumu Kinoshita
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Patent number: 8896914Abstract: An optical amplifying device includes an optical system including a first end and a second end, the optical system configured to receive signal light through the first end, to lead the received signal light to an optical amplifying medium, and to output the signal light amplified by the optical amplifying medium through the second end, the optical system including a first optical isolator and a second optical isolator which are arranged on respective sides of the optical amplifying medium, wherein with respect to a direction in which the signal light propagates, each of the first optical isolator and the second optical isolator is capable of allowing light propagating in the same direction to pass therethrough and blocking light propagating in the opposite direction, and the first optical isolator and the second optical isolator have different center isolation wavelengths for the light propagating in the opposite direction.Type: GrantFiled: June 14, 2012Date of Patent: November 25, 2014Assignee: Fujitsu LimitedInventors: Goji Nakagawa, Susumu Kinoshita
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Patent number: 8861557Abstract: A wavelength-tunable light source includes light sources having differing variable wavelength regions, where light sources having adjacent wavelength regions are distributed to different systems. The light sources are each set such that an end portion of the variable wavelength region of the light source overlaps an end portion of the variable wavelength region of another light source. A control unit selects and drives a first light source of a first system, varies a wavelength of the first light source, selects a second light source that is of a second system among the different systems and that has a wavelength region overlapping the variable wavelength region of the first light source, drives the second light source concurrently with the first light source and subsequently switches to the output light of the second light source, causing wavelength variation and executing continuous wavelength variation over a wide range.Type: GrantFiled: August 14, 2013Date of Patent: October 14, 2014Assignee: Fujitsu LimitedInventors: Goji Nakagawa, Takeshi Hoshida
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Publication number: 20140270781Abstract: An optical signal demodulator includes: an obtaining unit configured to obtain a spectrum of an optical signal generated by a second signal being superimposed on a first signal using frequency modulation; an identifying unit configured to identify a peak wavelength which is a wavelength corresponding to a peak position of the spectrum; and a demodulating unit configured to demodulate the second signal from the optical signal using a wavelength-variable filter to which a transmitted wavelength band has been set based on the peak wavelength.Type: ApplicationFiled: October 29, 2013Publication date: September 18, 2014Applicant: FUJITSU LIMITEDInventors: Goji NAKAGAWA, Kyosuke SONE, Shoichiro ODA, Yasuhiko AOKI
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Publication number: 20140205281Abstract: A monitoring apparatus, that monitors a wavelength tunable optical filter for filtering an optical signal to which a frequency modulation component is added, includes: an optical filter configured to filter the optical signal output from the wavelength tunable optical filter; a detector configured to detect amplitude of the frequency modulation component included in the optical signal output from the optical filter; a generator configured to generate an output-side amplitude distribution representing a distribution of the amplitude of the frequency modulation component detected by the detector, by sweeping a transmission wavelength of the optical filter; and a monitoring unit configured to monitor arrangement of a transmission wavelength band of the wavelength tunable optical filter with respect to a spectrum of the optical signal based on the output-side amplitude distribution generated by the generator.Type: ApplicationFiled: December 4, 2013Publication date: July 24, 2014Applicant: FUJITSU LIMITEDInventors: Kyosuke SONE, Yasuhiko AOKI, GOJI NAKAGAWA, Shoichiro ODA
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Patent number: 8757898Abstract: An optical coupling structure includes an optical amplifier array configured to include a plurality of optical amplifiers arranged in an array direction, an optical fiber array configured to include a plurality of optical fibers arranged in the array direction, and an optical coupling system that optically couples the optical amplifier array and the optical fiber array, wherein, in a non-array direction orthogonal to the array direction, the optical coupling system optically couples beams of light signals to an end face of the optical amplifier array in parallel with a waveguide direction of the optical amplifiers, and optically couples the beams to an end face of the optical fiber array obliquely to the end face of the optical fiber array in the non-array direction.Type: GrantFiled: January 28, 2013Date of Patent: June 24, 2014Assignee: Fujitsu LimitedInventor: Goji Nakagawa
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Publication number: 20140098828Abstract: A wavelength-tunable light source includes light sources having differing variable wavelength regions, where light sources having adjacent wavelength regions are distributed to different systems. The light sources are each set such that an end portion of the variable wavelength region of the light source overlaps an end portion of the variable wavelength region of another light source. A control unit selects and drives a first light source of a first system, varies a wavelength of the first light source, selects a second light source that is of a second system among the different systems and that has a wavelength region overlapping the variable wavelength region of the first light source, drives the second light source concurrently with the first light source and subsequently switches to the output light of the second light source, causing wavelength variation and executing continuous wavelength variation over a wide range.Type: ApplicationFiled: August 14, 2013Publication date: April 10, 2014Applicant: Fujitsu LimitedInventors: GOJI NAKAGAWA, Takeshi HOSHIDA
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Patent number: 8654440Abstract: An optical amplification module has a semiconductor optical amplifier, a package accommodating the semiconductor optical amplifier, and a first connector and a second connector holding respective collimator lenses and arranged in parallel on the package. A sum of bend radii of the first optical fiber and the second optical fiber is greater than a space between the first connector and the second connector.Type: GrantFiled: April 29, 2011Date of Patent: February 18, 2014Assignee: Fujitsu LimitedInventor: Goji Nakagawa
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Publication number: 20130236143Abstract: An optical coupling structure includes an optical amplifier array configured to include a plurality of optical amplifiers arranged in an array direction, an optical fiber array configured to include a plurality of optical fibers arranged in the array direction, and an optical coupling system that optically couples the optical amplifier array and the optical fiber array, wherein, in a non-array direction orthogonal to the array direction, the optical coupling system optically couples beams of light signals to an end face of the optical amplifier array in parallel with a waveguide direction of the optical amplifiers, and optically couples the beams to an end face of the optical fiber array obliquely to the end face of the optical fiber array in the non-array direction.Type: ApplicationFiled: January 28, 2013Publication date: September 12, 2013Applicant: FUJITSU LIMITEDInventor: Goji NAKAGAWA
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Patent number: 8437589Abstract: In an optical module, an optical element array is an array of optical elements. Further, a lens array is an array of a plurality of lenses. An output point of a light beam of each optical element of the optical element array is caused to coincide with a central line of a corresponding lens of the lens array, and the light beam is made incident on the lens and a parallel beam is output from the lens. When the output point of the light beam of the optical element coincides with an optical axis of the lens, an optical path within the optical element and the optical axis of the lens fail to coincide with each other.Type: GrantFiled: September 30, 2010Date of Patent: May 7, 2013Assignee: Fujitsu LimitedInventor: Goji Nakagawa
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Publication number: 20130038925Abstract: An optical amplifying device includes an optical system including a first end and a second end, the optical system configured to receive signal light through the first end, to lead the received signal light to an optical amplifying medium, and to output the signal light amplified by the optical amplifying medium through the second end, the optical system including a first optical isolator and a second optical isolator which are arranged on respective sides of the optical amplifying medium, wherein with respect to a direction in which the signal light propagates, each of the first optical isolator and the second optical isolator is capable of allowing light propagating in the same direction to pass therethrough and blocking light propagating in the opposite direction, and the first optical isolator and the second optical isolator have different center isolation wavelengths for the light propagating in the opposite direction.Type: ApplicationFiled: June 14, 2012Publication date: February 14, 2013Applicant: FUJITSU LIMITEDInventors: Goji Nakagawa, Susumu Kinoshita
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Publication number: 20120257272Abstract: An optical amplification apparatus includes a front-stage semiconductor optical amplifier which amplifies an input light and a rear-stage semiconductor optical amplifier which amplifies an amplified light outputted from the front-stage semiconductor optical amplifier. The front-stage semiconductor optical amplifier exercises auto level control of an output light by exercising variable control of driving current which flows according to applied voltage higher than light emitting threshold voltage of an internal optical amplification element. The rear-stage semiconductor optical amplifier performs gate switching of a transmitted light by exercising switching control of driving current. By doing so, distortion of a waveform is controlled and optical communication quality can be improved.Type: ApplicationFiled: March 12, 2012Publication date: October 11, 2012Applicant: FUJITSU LIMITEDInventors: Setsuo YOSHIDA, Susumu Kinoshita, George Ishikawa, Goji Nakagawa, Yutaka Kai, Kyosuke Sone, Keisuke Harada