Patents by Inventor Hiroto Kawakami
Hiroto Kawakami 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: 10243664Abstract: An optical modulator driver circuit (1) includes an amplifier (50, Q10, Q11, R10-R13), and a current amount adjustment circuit (51) capable of adjusting a current amount of the amplifier (50) in accordance with a desired operation mode. The current amount adjustment circuit (51) includes at least two current sources (IS10) that are individually ON/OFF-controllable in accordance with a binary control signal representing the desired operation mode.Type: GrantFiled: May 9, 2014Date of Patent: March 26, 2019Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Munehiko Nagatani, Hideyuki Nosaka, Toshihiro Itoh, Koichi Murata, Hiroyuki Fukuyama, Takashi Saida, Shin Kamei, Hiroshi Yamazaki, Nobuhiro Kikuchi, Hiroshi Koizumi, Masafumi Nogawa, Hiroaki Katsurai, Hiroyuki Uzawa, Tomoyoshi Kataoka, Naoki Fujiwara, Hiroto Kawakami, Kengo Horikoshi, Yves Bouvier, Mikio Yoneyama, Shigeki Aisawa, Masahiro Suzuki
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Publication number: 20180375607Abstract: An optical transmission system includes an optical transmission apparatus and an optical reception apparatus. The optical transmission apparatus includes a conversion unit that converts multiple binary data sequences into data in a predetermined signal format; a coding unit that generates multiple pieces of coded data by performing predetermined coding on each of the multiple pieces of converted data; an optical signal generation unit that generates multiple optical signals by converting the multiple pieces of coded data into optical signals; and a mode multiplexer that converts the multiple optical signals into different modes, generates a mode-division multiplexed optical signal by mode-division multiplexing the optical signals, and transmits the generated mode-division multiplexed optical signal to the optical reception apparatus.Type: ApplicationFiled: January 11, 2017Publication date: December 27, 2018Applicant: Nippon Telegraph and Telephone CorporationInventors: Kohki SHIBAHARA, Takayuki MIZUNO, Hiroto KAWAKAMI, Yutaka MIYAMOTO
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Publication number: 20180323878Abstract: An optical transmitter includes: an optical modulator including an MZ interferometer, a drive signal input electrode, and a phase difference adjustment bias electrode; a drive amplifier; a phase difference adjustment bias voltage generator; a dithering unit that applies dithering of a predetermined frequency to an amplitude of a drive signal or to a half-wave voltage of the MZ interferometer; a controller unit that changes a phase difference adjustment bias voltage based on a modulation component of the frequency that is superimposed onto modulated light that is output from the optical modulator, to thereby bias the MZ interferometer to a null point; and a synchronous detection circuit that synchronously detects the modulation component of the frequency that is superimposed onto the modulated light. The controller unit changes the phase difference adjustment bias voltage such that a result of synchronous detection by the synchronous detection circuit becomes maximized or minimized.Type: ApplicationFiled: November 10, 2016Publication date: November 8, 2018Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Hiroto KAWAKAMI, Shoichiro KUWAHARA, Akira HIRANO
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Patent number: 10090921Abstract: A light modulation device detects a power of the modulated optical signal modulated by each of an I-component optical modulator and a Q-component optical modulator, synchronously-detects a component of a frequency fd from the power of the modulated optical signal, outputs a dither signal of a frequency fd/n (where n is a positive integer equal to or larger than 1) applied to a first bias voltage or a second bias voltage when adjusting the first bias voltage or the second bias voltage, outputs two dither signals having a frequency fd/m (where m is a positive integer equal to or larger than 1, where n<m), which are mutually orthogonal to each other, applied to the first and second bias voltages when adjusting a third bias voltage, and adjusting bias voltages by increasing or decreasing bias voltages based on a synchronous detection result.Type: GrantFiled: April 10, 2015Date of Patent: October 2, 2018Assignees: Nippon Telegraph And Telephone Corporation, NTT Electronics CorporationInventors: Mikio Yoneyama, Hiroto Kawakami, Takashi Ono, Akihiko Matsuura, Tomoyoshi Kataoka, Katsuya Tanaka, Masahiro Tachibana, Yuya Oyama
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Publication number: 20170117961Abstract: A light modulation device detects a power of the modulated optical signal modulated by each of an I-component optical modulator and a Q-component optical modulator, synchronously-detects a component of a frequency fd from the power of the modulated optical signal, outputs a dither signal of a frequency fd/n (where n is a positive integer equal to or larger than 1) applied to a first bias voltage or a second bias voltage when adjusting the first bias voltage or the second bias voltage, outputs two dither signals having a frequency fd/m (where m is a positive integer equal to or larger than 1, where n<m), which are mutually orthogonal to each other, applied to the first and second bias voltages when adjusting a third bias voltage, and adjusting bias voltages by increasing or decreasing bias voltages based on a synchronous detection result.Type: ApplicationFiled: April 10, 2015Publication date: April 27, 2017Applicants: NIPPON TELEGRAPH AND TELEPHONE CORPORATION, NTT Electronics CorporationInventors: Mikio YONEYAMA, Hiroto KAWAKAMI, Takashi ONO, Akihiko MATSUURA, Tomoyoshi KATAOKA, Katsuya TANAKA, Masahiro TACHIBANA, Yuya OYAMA
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Publication number: 20160087727Abstract: An optical modulator driver circuit (1) includes an amplifier (50, Q10, Q11, R10-R13), and a current amount adjustment circuit (51) capable of adjusting a current amount of the amplifier (50) in accordance with a desired operation mode. The current amount adjustment circuit (51) includes at least two current sources (IS10) that are individually ON/OFF-controllable in accordance with a binary control signal representing the desired operation mode.Type: ApplicationFiled: May 9, 2014Publication date: March 24, 2016Inventors: Munehiko Nagatani, Hideyuki Nosaka, Toshihiro Itoh, Koichi Murata, Hiroyuki Fukuyama, Takashi Saida, Shin Kamei, Hiroshi Yamazaki, Nobuhiro Kikuchi, Hiroshi Koizumi, Masafumi Nogawa, Hiroaki Katsurai, Hiroyuki Uzawa, Tomoyoshi Kataoka, Naoki Fujiwara, Hiroto Kawakami, Kengo Horikoshi, Yves Bouvier, Mikio Yoneyama, Shigeki Aisawa, Masahiro Suzuki
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Patent number: 9116368Abstract: An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.Type: GrantFiled: August 21, 2012Date of Patent: August 25, 2015Assignee: Nippon Telegraph and Telephone CorporationInventors: Hiroto Kawakami, Eiji Yoshida, Yutaka Miyamoto
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Patent number: 9020361Abstract: An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by ?/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage V? of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogonaType: GrantFiled: September 7, 2010Date of Patent: April 28, 2015Assignees: Nippon Telegraph and Telephone Corporation, NTT Electronics CorporationInventors: Hiroto Kawakami, Eiji Yoshida, Masahiro Tachibana
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Publication number: 20140153077Abstract: An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.Type: ApplicationFiled: August 21, 2012Publication date: June 5, 2014Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Hiroto Kawakami, Eiji Yoshida, Yutaka Miyamoto
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Publication number: 20120155865Abstract: An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by ?/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage V? of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogonaType: ApplicationFiled: September 7, 2010Publication date: June 21, 2012Applicants: NTT ELECTRONICS CORPORATION, NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Hiroto Kawakami, Eiji Yoshida, Masahiro Tachibana
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Patent number: 7995930Abstract: The present invention relates to an optical receiver, in which the transmittance of a Mach-Zehnder interferometer can be locked at a normal operation point in a simple structure and control. A transmittance detecting circuit and a minute modulation signal detecting circuit are provided in parallel after a balanced optical receiver, and a switch is selectively connectable either a minute modulation signal detecting circuit and a transmittance detecting circuit. In the initial stage of frequency pull-in, the switch is set to connect the transmittance detecting circuit to the synchronous detection circuit. If the transmittance detecting circuit detects that the transmittance of the Mach-Zehnder interferometer at the carrier frequency becomes a desired transmittance, the connection of the switch is switched from the transmittance detecting circuit to the minute modulation signal detecting circuit.Type: GrantFiled: May 19, 2006Date of Patent: August 9, 2011Assignees: NTT Electronics Corporation, Nippon Telegraph and Telephone CorporationInventors: Mikio Yoneyama, Fumiaki Saitou, Shigeru Ono, Yosuke Takeuchi, Kazushige Yonenaga, Shoichiro Kuwahara, Eiji Yoshida, Yutaka Miyamoto, Hiroto Kawakami
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Publication number: 20090097867Abstract: The present invention relates to an optical receiver, in which the transmittance of a Mach-Zehnder interferometer can be locked at a normal operation point in a simple structure and control. A transmittance detecting circuit and a minute modulation signal detecting circuit are provided in parallel after a balanced optical receiver, and a switch is selectively connectable either a minute modulation signal detecting circuit and a transmittance detecting circuit. In the initial stage of frequency pull-in, the switch is set to connect the transmittance detecting circuit to the synchronous detection circuit. If the transmittance detecting circuit detects that the transmittance of the Mach-Zehnder interferometer at the carrier frequency becomes a desired transmittance, the connection of the switch is switched from the transmittance detecting circuit to the minute modulation signal detecting circuit.Type: ApplicationFiled: May 19, 2006Publication date: April 16, 2009Inventors: Mikio Yoneyama, Fumiaki Saitou, Shigeru Ono, Yosuke Takeuchi, Kazushige Yonenaga, Shoichiro Kuwahara, Eiji Yoshida, Yutaka Miyamoto, Hiroto Kawakami
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Patent number: 7379236Abstract: An optical fiber communication system is provided which uses remote pumping that is capable of improving pumping efficiency and reducing a noise figure. A coupler (20) of a linear repeater (18) couples signal light to pumping light outputted from a pumping light source (19). The outputted signal light and pumping light reach a linear repeater (25) through transmission fibers (22 to 24) and remote pumping modules (27F and 27R). A coupler (30) of the linear repeater (25) couples the signal light to the pumping light supplied from a pumping light source (29), to output the signal light and the pumping light to the transmission fiber (24). The remote pumping module (27F) divides the pumping light propagated in the transmission fiber (22), from the signal light. The remote pumping module 27F branches the divided pumping light in two directions with a predetermined ratio. After branching, each of the branched pumping light is coupled to the signal light to be supplied to both ends of an erbium-doped fiber.Type: GrantFiled: July 5, 2004Date of Patent: May 27, 2008Assignee: Nippon Telegraph and Telephone CorporationInventors: Hiroji Masuda, Hiroto Kawakami, Yutaka Miyamoto
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Publication number: 20070003286Abstract: An optical fiber communication system is provided which uses remote pumping that is capable of improving pumping efficiency and reducing a noise figure. A coupler (20) of a linear repeater (18) couples signal light to pumping light outputted from a pumping light source (19). The outputted signal light and pumping light reach a linear repeater (25) through transmission fibers (22 to 24) and remote pumping modules (27F and 27R). A coupler (30) of the linear repeater (25) couples the signal light to the pumping light supplied from a pumping light source (29), to output the signal light and the pumping light to the transmission fiber (24). The remote pumping module (27F) divides the pumping light propagated in the transmission fiber (22), from the signal light. The remote pumping module 27F branches the divided pumping light in two directions with a predetermined ratio. After branching, each of the branched pumping light is coupled to the signal light to be supplied to both ends of an erbium-doped fiber.Type: ApplicationFiled: July 5, 2004Publication date: January 4, 2007Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATIONInventors: Hiroji Masuda, Hiroto Kawakami, Yutaka Miyamoto
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Patent number: 6263139Abstract: To suppress S/N degradation due to optical amplification and generation of a nonlinear optical effect in a dispersion compensating fiber, and compensate for a loss due to the dispersion compensating fiber without incorporating a long fiber inside a receiver, part of an optical transmission line is constructed by a dispersion compensating fiber and at least part of the optical transmission line is designed to have a Raman gain or a distributed gain. A pump light to obtain a Raman gain or a distributed gain is transmitted from at least one of a transmitter, a receiver, and a repeater to the optical transmission line.Type: GrantFiled: November 9, 1999Date of Patent: July 17, 2001Assignee: Nippon Telegraph and Telephone CorporationInventors: Hiroto Kawakami, Yutaka Miyamoto
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Patent number: 5265136Abstract: A sodium cooled fast ractor comprises a reactor vessel in which a liquid metal coolant is accommodated, a core disposed substantially a lower central portion of the reactor vessel in an installed state, a core support structure secured to the reactor vessel for supporting the core, the core support structure dividing an interior of the reactor vessel into a high-pressure plenum below the core and a low-pressure plenum above the high-pressure plenum, a circulation pump unit for applying a discharge pressure to the liquid metal coolant and circulating the same, and an intermediate heat exchanger for performing a heat exchanging operation of the coolant in the reactor vessel. The circulation pump unit is composed of an electromagnetic circulation pump provided with a discharge port and a closed gas space, which is filled up with a closed gas, defined above and communicated with the discharge port.Type: GrantFiled: October 1, 1992Date of Patent: November 23, 1993Assignee: Kabushiki Kaisha ToshibaInventors: Hiroshi Yamazaki, Hiroto Kawakami