Patents by Inventor Yuichi Akiyama
Yuichi Akiyama 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: 20110026935Abstract: An optical signal transmitter includes: first outer modulator to generate first modulated optical signal, the first outer modulator including a pair of optical paths and a first phase shifter to give phase difference to the pair of optical paths; second outer modulator to generate second modulated optical signal, the second outer modulator including a pair of optical paths and a second phase shifter to give phase difference to the pair of optical paths; combiner to generate polarization multiplexed optical signal by combining the first and second modulated optical signals; phase controller to control the phase difference by the first phase shifter to A??? and control the phase difference by the second phase shifter to A+??; and power controller to control at least one of the first and second outer modulators based on AC component of the polarization multiplexed optical signal.Type: ApplicationFiled: July 19, 2010Publication date: February 3, 2011Applicant: FUJITSU LIMITEDInventors: Yuichi Akiyama, Noriaki Mizuguchi
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Patent number: 7873283Abstract: The invention aims to provide a monitoring method that can measure an optical SNR in an ultra high speed optical transmission system with high accuracy, and an optical transmission system using the same. To this end, in the optical transmission system to which the monitoring method of the present invention is applied, the degree of polarization of an optical signal transmitted from an optical transmission apparatus to an optical receiving apparatus via an optical transmission path is measured by a DOP measuring device, and an optical SNR of the optical signal is determined by an optical SNR calculation circuit based on a measured value of the degree of polarization.Type: GrantFiled: September 16, 2003Date of Patent: January 18, 2011Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Takafumi Terahara
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Patent number: 7853148Abstract: An optical add/drop multiplexer includes a first optical coupler receiving an optical signal including a plurality of multiplexed wavelengths, a wavelength blocker receiving the optical signal from the first optical coupler, and blocking at least one wavelength of the plurality of multiplexed wavelengths, a first wavelength selective switch, having one input port receiving the outputted optical signal from the first optical coupler and a plurality of output ports, demultiplexing a plurality of arbitrarily selected multiplexed wavelengths from the received optical signal, a second wavelength selective switch, having a plurality of input ports, each input port receiving a different optical signal and one output port, multiplexing a plurality of arbitrarily selected wavelength signals on the plurality of input ports, and a second optical coupler receiving the optical signal output from the wavelength blocker and multiplexed wavelength signal from the second wavelength selective switch.Type: GrantFiled: February 13, 2009Date of Patent: December 14, 2010Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Takafumi Terahara, Hiroki Ooi, Jens C. Rasmussen, Akira Miura, Akihiko Isomura
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Patent number: 7848659Abstract: A data modulator unit generates a DQPSK optical signal in accordance with a data signal. A phase shift unit provides a phase difference of ?/2 between a pair of arms. A photodetector converts an output signal of the data modulator unit into an electrical signal. A filter is a low-pass filter with a cut-off frequency lower than a symbol frequency, and filters an output signal of the photodetector. A monitor unit detects power of an output signal of the filter. A phase difference control unit adjusts the amount of phase shift in the phase shift unit so as to minimize power of an output signal of the filter.Type: GrantFiled: December 12, 2005Date of Patent: December 7, 2010Assignee: Fujitsu LimitedInventors: Akira Miura, Kentaro Nakamura, Hiroshi Onaka, Yuichi Akiyama, Hiroki Ooi, Jens Rasmussen, Takeshi Hoshida
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Patent number: 7817923Abstract: A phase shift unit provides a prescribed phase difference (?/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal f0 is superimposed on one of the optical signals. A signal of which phase is shifted by ?/2 from the low-frequency signal f0 is superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2f0 component contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2f0 component becomes the minimum.Type: GrantFiled: December 30, 2005Date of Patent: October 19, 2010Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Takeshi Hoshida, Yutaka Kai, Hiroki Ooi, Kentaro Nakamura, Naoki Kuwata, Yoshinori Nishizawa, Tomoo Takahara, Masahiro Yuki
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Publication number: 20100254718Abstract: In-phase signal light and quadrature-phase signal light obtained by mixing input light and local light with each other are converted into digital signals. The quality of a signal to be received is monitored with reference to information obtained through digital signal processing, and the power ratio between the input signal light and the local light that are to be mixed with each other are controlled on the basis of the result of the monitoring.Type: ApplicationFiled: March 8, 2010Publication date: October 7, 2010Applicant: Fujitsu LimitedInventors: Shoichiro ODA, Takeshi Hoshida, Hisao Nakashima, Takahito Tanimura, Yuichi Akiyama
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Publication number: 20100254716Abstract: An object of the invention is to provide a control system in which the phase shift between drive signals of an optical modulator can be reliably detected and compensated by a simple configuration. To this end, a control apparatus of the invention, for an optical modulator generating a signal light of a CS-RZ modulation system or the like by two LN modulators connected in series, detects the phase shift between drive signals given to the former and latter stage LN modulators, or judges the phase shift between the drive signals based on intensity information of the electric spectrum of the signal light output from the optical modulator, to control the phases of the drive signals so as to minimize the phase shift. As a result, the phase shift between the drive signals can be reliably detected and compensated by an electric circuit with a simple configuration.Type: ApplicationFiled: April 23, 2010Publication date: October 7, 2010Applicant: Fujitsu LimitedInventors: Yuichi Akiyama, Hiroki Ooi
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Patent number: 7792428Abstract: A core unit arranged in a transmission path includes a through path for causing an input signal to an input port to pass through to an output port, a drop-side port 25a that drops the input signal having a predetermined wavelength, and an add-side port 25b that adds channel having a predetermined wavelength to the input light.Type: GrantFiled: August 16, 2005Date of Patent: September 7, 2010Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Takafumi Terahara, Hiroki Ooi, Jens C. Rasmussen, Akira Miura, Akihiko Isomura
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Patent number: 7773283Abstract: According to an aspect of an embodiment, an optical modulation device includes a Mach-Zehnder modulator and a controller. The Mach-Zehnder modulator is supplied a drive signal and a bias voltage. The Mach-Zehnder modulator modulates inputted light on the bases of the drive signal and the bias voltage. The drive signal selectively is superimposes a predetermined frequency signal. The bias voltage selectively is superimposes the predetermined frequency signal. The controller selects a superimposing target which is the drive signal or the bias voltage so as to change modulation formats.Type: GrantFiled: March 28, 2008Date of Patent: August 10, 2010Assignee: Fujitsu LimitedInventors: Toshiki Tanaka, Hideyuki Miyata, Yuichi Akiyama, Takeshi Hoshida
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Patent number: 7734192Abstract: An object of the invention is to provide a control system in which the phase shift between drive signals of an optical modulator can be reliably detected and compensated by a simple configuration. To this end, a control apparatus of the invention, for an optical modulator generating a signal light of a CS-RZ modulation system or the like by two LN modulators connected in series, detects the phase shift between drive signals given to the former and latter stage LN modulators, or judges the phase shift between the drive signals based on intensity information of the electric spectrum of the signal light output from the optical modulator, to control the phases of the drive signals so as to minimize the phase shift. As a result, the phase shift between the drive signals can be reliably detected and compensated by an electric circuit with a simple configuration.Type: GrantFiled: July 23, 2008Date of Patent: June 8, 2010Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Hiroki Ooi
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Patent number: 7720383Abstract: An optical transmission apparatus has a first wavelength selective switch (WSS) for route switching, provided with respect to each route, to selectively output signal light from a first input route to second through Nth output routes and to selectively output signal lights from second through Nth input routes to a first output route, for every wavelength, a second WSS for add and drop, to selectively output a signal light from an add port to the first through Nth output routes via the first WSS for every wavelength, and to selectively output the signal lights from the first through Nth input routes to a drop port via the first WSS for every wavelength, and an optical coupler to multiplex each of the signal lights output from the first WSS to the output routes and each of the signal lights output from the second WSS to the output routes, for every route, and to send multiplexed signal light to a first WSS of an other route, and to branch and supply multiplexed signal light input from said other route to the fiType: GrantFiled: January 10, 2007Date of Patent: May 18, 2010Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Takafumi Terahara, Hiroki Ooi
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Patent number: 7711270Abstract: The optical node connects N networks to each other (where N is an integer larger than one). Each of the N networks respectively includes a first transmission path and a second transmission path. The optical node includes a switching unit that connects the first transmission path of one network of the N networks to other (N?1) networks; a failure detector that detects failure in the first transmission path of the network; and a control unit that causes the switching unit to connect the second transmission path of the network to the other (N?1) networks when the failure is detected.Type: GrantFiled: December 27, 2005Date of Patent: May 4, 2010Assignee: Fujitsu LimitedInventors: Hiroki Ooi, Takafumi Terahara, Jens C. Rasmussen, Akira Miura, Akihiko Isomura, Yuichi Akiyama
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Publication number: 20100098435Abstract: An optical DQPSK modulator comprises a pair of phase modulators. Each of the pair of the phase modulators is provided with first and second driving signals. The first and second driving signals are amplified by first and second amplifiers, respectively. An RZ intensity modulator generates an optical RZ-DQPSK signal from an optical DQPSK signal output from the optical DQPSK modulator. A photodetector generates a monitor signal from the optical RZ-DQPSK signal. A gain adjuster unit adjusts the gains of the first and second amplifiers so as to minimize the power of the monitor signal.Type: ApplicationFiled: December 17, 2009Publication date: April 22, 2010Applicant: Fujitsu LimitedInventor: Yuichi AKIYAMA
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Publication number: 20100080571Abstract: An optical signal transmitter includes first and second modulation units, a combiner, and a control unit. The first and second modulation units generate first and second modulated optical signals, respectively. The combiner combines the first and second modulated optical signals to generate a polarization multiplexed optical signal. The control unit controls at least one of the first and second modulation units so that the optical powers of the first and second modulated optical signals become approximately equal to each other.Type: ApplicationFiled: June 30, 2009Publication date: April 1, 2010Applicant: FUJITSU LIMITEDInventors: Yuichi Akiyama, Hideyuki Miyata, Takeshi Hoshida
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Publication number: 20100067914Abstract: The polarization multiplexed light transmitter takes out a part of a polarization multiplexed light to be transmitted as a monitor light; makes orthogonal polarization components contained in the monitor light to interfere with each other, to generate a polarization interfering light; converts the polarization interfering light into an electric signal; measures the power of an alternate current component contained in the electric signal after eliminating a direct current component thereof; and feedback controls delay amount varying sections so that an inter-polarized channel delay time judged based on a change in the measured power reaches a predetermined value. Thus, the delay time between the orthogonal polarization components in the polarization multiplexed light can be varied flexibly at a high speed with a simple configuration, and thus, it becomes possible to suppress transmission characteristics degradation of the polarization multiplexed light due to a change in system state.Type: ApplicationFiled: September 4, 2009Publication date: March 18, 2010Applicant: FUJITSU LIMITEDInventors: Toshiki Tanaka, Yuichi Akiyama, Masahiro Yuki, Hideyuki Miyata
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Patent number: 7657190Abstract: An optical DQPSK modulator comprises a pair of phase modulators. Each of the pair of the phase modulators is provided with first and second driving signals. The first and second driving signals are amplified by first and second amplifiers, respectively. An RZ intensity modulator generates an optical RZ-DQPSK signal from an optical DQPSK signal output from the optical DQPSK modulator. A photodetector generates a monitor signal from the optical RZ-DQPSK signal. A gain adjuster unit adjusts the gains of the first and second amplifiers so as to minimize the power of the monitor signal.Type: GrantFiled: May 17, 2006Date of Patent: February 2, 2010Assignee: Fujitsu LimitedInventor: Yuichi Akiyama
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Patent number: 7603007Abstract: The improved quadrature phase shift keying modulator has a structure such that the average light output power of phase-shift keying modulation light output from the combining unit is changed according to the phase difference between the first and the second optical signal after being combined by means of applying driving signals different in eye crossing percentage by the first modulator and the second modulator, respectively, and has a power monitor monitoring the average light output power of quadrature phase-shift keying modulated light and a phase shift controlling unit which performs feedback control of the phase shift amount in the phase shifting unit based on the average light output power monitored by the power monitor.Type: GrantFiled: September 22, 2008Date of Patent: October 13, 2009Assignee: Fujitsu LimitedInventors: Takafumi Terahara, Takeshi Hoshida, Kentaro Nakamura, Yuichi Akiyama, Hiroki Ooi, Jens C. Rasmussen, Akira Miura
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Publication number: 20090244685Abstract: The optical modulator branches an input light into (2×N) lights in an optical branching section, and then phase modulates each of the branched lights in (2×N) phase modulating sections, and couples the phase modulated lights in an optical coupling section and generates a quadrature amplitude modulated (QAM) signal light having a 4N value. At this time, a relative difference of optical phases of the phase modulated lights is variably adjusted by an optical phase adjusting section. Moreover, a power ratio of the phase modulated lights is variably adjusted with an optical power adjusting section. As a result, it is possible to output 4N QAM signal light, with good signal quality.Type: ApplicationFiled: November 19, 2008Publication date: October 1, 2009Applicant: Fujitsu LimitedInventors: Takeshi Hoshida, Yuichi Akiyama
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Publication number: 20090226165Abstract: An apparatus includes an oscillator circuit configured to generate a certain oscillation signal, an adder configured to add the oscillation signal to the tap coefficient of any of one or more taps of the transversal filter, a signal-quality measurer configured to measure a signal quality of a signal output from the transversal filter, and a tap-coefficient adjuster configured to control the value of the tap coefficient so that an optimal amount of shift in the signal quality of the output signal is achieved when the oscillation signal is added to the tap coefficient.Type: ApplicationFiled: March 4, 2009Publication date: September 10, 2009Applicant: Fujitsu LimitedInventors: Toshiki Tanaka, Yuichi Akiyama
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Publication number: 20090148166Abstract: An optical add/drop multiplexer includes a first optical coupler receiving an optical signal including a plurality of multiplexed wavelengths, a wavelength blocker receiving the optical signal from the first optical coupler, and blocking at least one wavelength of the plurality of multiplexed wavelengths, a first wavelength selective switch, having one input port receiving the outputted optical signal from the first optical coupler and a plurality of output ports, demultiplexing a plurality of arbitrarily selected multiplexed wavelengths from the received optical signal, a second wavelength selective switch, having a plurality of input ports, each input port receiving a different optical signal and one output port, multiplexing a plurality of arbitrarily selected wavelength signals on the plurality of input ports, and a second optical coupler receiving the optical signal output from the wavelength blocker and multiplexed wavelength signal from the second wavelength selective switch.Type: ApplicationFiled: February 13, 2009Publication date: June 11, 2009Applicant: FUJITSU LIMITEDInventors: Yuichi AKIYAMA, Takafumi Terahara, Hiroki Ooi, Jens C. Rasmussen, Akira Miura, Akihiko Isomura