Patents by Inventor Yutaka Kai
Yutaka Kai 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).
-
Publication number: 20120293228Abstract: A level control circuit that generates output signal for level control includes: a control information storage that stores control information corresponding to a signal level, a control information circuit that outputs the output signal for level control corresponding to the signal level of a first input signal based on the control information stored in the control information storage; and an information update circuit that updates the control information of the control information storage according to the signal level of a second input signal.Type: ApplicationFiled: April 19, 2012Publication date: November 22, 2012Applicant: FUJITSU LIMITEDInventors: Yutaka KAI, Setsuo YOSHIDA, Taku YOSHIDA, Keisuke HARADA
-
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
-
Patent number: 8275258Abstract: An optical communication base station which receives an upstream optical signal having an upstream bit rate specific to each one of a plurality of lower order communication units from a corresponding one of the plurality of lower order communication units, and which transmits a downstream optical signal having a downstream bit rate specific to each one of the plurality of lower order communication units to a designated one of the plurality of lower order communication units, includes; a first optical signal conversion unit which changes the bit rate of the upstream optical signal and thereby converts the upstream optical signal into a fixed bit-rate inter-station optical signal; and a second optical signal conversion unit which converts the inter-station optical signal into the downstream optical signal by changing the bit rate of the inter-station optical signal according to the designated one of the plurality of lower order communication units.Type: GrantFiled: August 5, 2009Date of Patent: September 25, 2012Assignee: Fujitsu LimitedInventors: Yutaka Kai, Yasuhiko Aoki
-
Patent number: 8179593Abstract: An optical-switch drive circuit including a driver unit that generates, in response to a control signal, an on/off signal for driving a semiconductor optical amplifier gate switch, and a buffer unit having a high input impedance and connected between an output terminal outputting the on/off signal and the semiconductor optical amplifier gate switch. In the optical-switch drive circuit the buffer unit may include a high-resistance voltage divider that is connected with the output terminal, and an operational amplifier that buffers, and provides to the semiconductor optical amplifier gate switch, a divided voltage of the voltage divider.Type: GrantFiled: March 18, 2009Date of Patent: May 15, 2012Assignee: Fujitsu LimitedInventors: Masaji Noguchi, Yutaka Kai, Setsuo Yoshida
-
Patent number: 8170416Abstract: An optical switching device the size and costs of which are reduced by decreasing the number of switching elements and which can flexibly accommodate the expansion of the number of ports. An optical demultiplexing section has 2n (n=1, 2, 3, . . . ) input ports and 2m (m>n) output ports and includes demultiplexing couplers for demultiplexing input optical packets. A switch fabric section includes optical gate elements for switching optical packets outputted from the optical demultiplexing section by switch drive control. An optical multiplexing section has 2m input ports and 2n output ports and includes multiplexing couplers for multiplexing the optical packets which pass through the optical gate elements. A scheduler exercises control over an entire optical packet switching process.Type: GrantFiled: March 24, 2008Date of Patent: May 1, 2012Assignee: Fujitsu LimitedInventors: Yutaka Kai, Yasuhiko Aoki
-
Patent number: 8155517Abstract: An optical packet switching apparatus includes plural optical switches, an optical switching section that switches a path of an optical packet transmitted thereto according to the switch control signal to output the optical packet, and a control section that takes out a header portion representing a destination of the optical packet transmitted, photoelectrically converts the header to generate the switch control signal according to the destination to transmit the switch control signal to the optical switching section and controls the optical switch. The apparatus further includes a light monitor section that monitors a light quantity level of the optical packet transmitted and a light quantity level of the optical packet to be sent out, and an abnormality recognizing section that recognizes an effective timing of monitoring of the light quantity levels based on the switching control signal, and recognizes an abnormality based on the light quantity levels at the timing.Type: GrantFiled: October 13, 2009Date of Patent: April 10, 2012Assignee: Fujitsu LimitedInventors: Keisuke Harada, Yutaka Kai
-
Publication number: 20120082465Abstract: 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: ApplicationFiled: September 10, 2010Publication date: April 5, 2012Applicant: Fujitsu LimitedInventors: Yuichi Akiyama, Takeshi Hoshida, Akira Miura, Yutaka Kai, Hiroki Ooi, Jens Rasmussen, Kentaro Nakamura, Naoki Kuwata, Yoshinori Nishizawa, Tomoo Takahara, Masahiro Yuki
-
Patent number: 8139903Abstract: A driving circuit of a semiconductor optical amplifier type gate switch constituting a matrix optical switch is provided with an operation amplifier into which a driving signal is input and from which a current corresponding to the driving signal is output, an inductance element provided at an output terminal of the operation amplifier, and a circuit composed of a diode element and a resistor element connected in parallel and provided between the inductance element and the semiconductor optical amplifier.Type: GrantFiled: November 1, 2010Date of Patent: March 20, 2012Assignee: Fujitsu LimitedInventors: Masaji Noguchi, Tomohiro Ueno, Yutaka Kai, Setsuo Yoshida
-
Patent number: 8107813Abstract: A drive circuit includes a first transistor that is controlled to be in on or off state in response to a control signal, and outputs, in on state, a positive current which is input from a first operational amplifier connected with a drain of the first transistor to a semiconductor optical amplifier; and a second transistor that is connected with a source of the first transistor, and is in inverse on or off state to the state of the first transistor. The drive circuit also includes a negative voltage circuit that is connected to a source of the second transistor, and outputs, when the second transistor is in on state, a negative current to the semiconductor optical amplifier.Type: GrantFiled: January 26, 2009Date of Patent: January 31, 2012Assignee: Fujitsu LimitedInventors: Setsuo Yoshida, Yutaka Kai, Masaji Noguchi
-
Publication number: 20110254608Abstract: A level control circuit that generates output signal for level control includes: a control information storage that stores control information corresponding to a signal level, a control information circuit that outputs the output signal for level control corresponding to the signal level of a first input signal based on the control information stored in the control information storage; and an information update circuit that updates the control information of the control information storage according to the signal level of a second input signal.Type: ApplicationFiled: April 14, 2011Publication date: October 20, 2011Applicant: FUJITSU LIMTEDInventors: Yutaka KAI, Setsuo YOSHIDA, Taku YOSHIDA, Keisuke HARADA
-
Patent number: 8032028Abstract: Optical add/drop nodes are used in a network having a pair of optical transmission paths for transmitting optical signals in opposite directions to each other. Each add/drop node comprises a variable split ratio optical coupler for splitting an optical signal output from a transmitter. The split ratio of the variable split ratio optical coupler is set such that the optical power levels of the signals added through the respective optical add/drop nodes are equal to one another respectively on the pair of optical transmission paths.Type: GrantFiled: March 2, 2007Date of Patent: October 4, 2011Assignee: Fujitsu LimitedInventors: Yutaka Takita, Yutaka Kai, Yasuhiko Aoki, Kyosuke Sone
-
Patent number: 8019219Abstract: An optical switch section that switches the path of an optical packet transmitted thereto and outputs the optical packet, and a control section that generates multiple switch control signals in accordance with the destination of an optical packet transmitted thereto, transmits the multiple control signals to the optical switch section through multiple signal transmission lines and controls the ON/OFF states of multiple optical switches are included, and delay measuring means for measuring a difference in delay time among the multiple signal transmission lines is provided. In this case, the control section adjusts the transmission times of the multiple switch control signals such that the difference in delay time measured by the delay measuring means can be cancelled and that the multiple switch control signals transmitted through the multiple signal transmission lines can arrive at the multiple optical switches simultaneously and transmits the multiple switch control signals.Type: GrantFiled: March 11, 2008Date of Patent: September 13, 2011Assignee: Fujitsu LimitedInventors: Koji Matsunaga, Yutaka Kai
-
Publication number: 20110116798Abstract: An optical communication network includes a plurality of optical transmission devices, a communication path, an optical repeater, and a supervisory controller that includes a supervisory control information sender which is installed on at least one of one of the optical transmission devices and the optical repeater and controls a drive signal supplied to a semiconductor optical amplifier that amplifies and outputs input signal light onto the communication path on the basis of the supervisory control information, and a supervisory control information receiver that receives the light which has been output from a semiconductor optical amplifier and transmitted through the communication path, converts the received light to an electric signal and identifies the supervisory control information on the basis of an intensity-modulated component of the total power of the electric signal in at least the other of one of the optical transmission devices and the optical repeater.Type: ApplicationFiled: November 15, 2010Publication date: May 19, 2011Applicant: FUJITSU LIMITEDInventor: Yutaka KAI
-
Publication number: 20110050293Abstract: A driving circuit of a semiconductor optical amplifier type gate switch constituting a matrix optical switch is provided with an operation amplifier into which a driving signal is input and from which a current corresponding to the driving signal is output, an inductance element provided at an output terminal of the operation amplifier, and a circuit composed of a diode element and a resistor element connected in parallel and provided between the inductance element and the semiconductor optical amplifier.Type: ApplicationFiled: November 1, 2010Publication date: March 3, 2011Applicant: FUJITSU LIMITEDInventors: Masaji Noguchi, Tomohiro Ueno, Yutaka Kai, Setsuo Yoshida
-
Patent number: 7898341Abstract: A non-inverting amplifier circuit is disclosed that includes an operational amplifier and a preemphasis circuit connected between the operational amplifier and a signal source. The preemphasis circuit is configured to compensate for the internal delay of a load connected to the output of the operational amplifier by emphasizing a high-frequency component of a signal fed from the signal source.Type: GrantFiled: August 26, 2008Date of Patent: March 1, 2011Assignee: Fujitsu LimitedInventors: Tomohiro Ueno, Masaji Noguchi, Yutaka Kai, Setsuo Yoshida
-
Publication number: 20110006124Abstract: A temperature control apparatus controlling the temperature of an optical element that is driven in response to a drive current that is applied, the temperature control apparatus including: a temperature controller that changes the temperature of the optical element; and a controller that controls current to the temperature controller, wherein the controller determines a time from when an amount of heat from the temperature controller has been generated by the current control until the amount of heat reaches the optical element and controls the current to the temperature controller the determined time before the drive current is applied to the optical element.Type: ApplicationFiled: July 9, 2010Publication date: January 13, 2011Applicant: FUJITSU LIMITEDInventor: Yutaka KAI
-
Patent number: 7848600Abstract: A driving circuit of a semiconductor optical amplifier type gate switch constituting a matrix optical switch is provided with an operation amplifier into which a driving signal is input and from which a current corresponding to the driving signal is output, an inductance element provided at an output terminal of the operation amplifier, and a circuit composed of a diode element and a resistor element connected in parallel and provided between the inductance element and the semiconductor optical amplifier.Type: GrantFiled: March 27, 2007Date of Patent: December 7, 2010Assignee: Fujitsu LimitedInventors: Masaji Noguchi, Tomohiro Ueno, Yutaka Kai, Setsuo Yoshida
-
Patent number: 7826744Abstract: An optical network system is disclosed by which flexible wavelength path setting can be performed in accordance with tree-shaped and star-shaped network topology. A central node includes a multiplexing section for multiplexing optical signals transmitted from user nodes and inputted thereto, and a central node side branching section for branching the optical signal multiplexed by the multiplexing section and supplying the branched optical signals to the user nodes. Each of the user nodes includes a transmission section capable of outputting an optical signal to which transmission wavelengths different from those of the other user nodes are set, and a reception section for extracting selected optical wavelength components from the branched light supplied thereto from the central node side branching section and extracting optical signals from the extracted optical wavelength components.Type: GrantFiled: December 22, 2005Date of Patent: November 2, 2010Assignee: Fujitsu LimitedInventors: Hideyuki Miyata, Goji Nakagawa, Yutaka Kai
-
Publication number: 20100266293Abstract: A relay apparatus including: a first interface 11 that branches an optical signal that is input in a first direction from one side of the optical transmission line, and directs the optical signal to a first path and a second path, the first path being a processing path of an optical signal having a first transmission speed, the second path being a processing path of an optical signal having a second transmission speed that is different from the first transmission speed; a processing section 12 that executes processing on an optical signal propagating through each of the paths in accordance with a corresponding transmission speed; and a second interface 13 that binds the first path and the second path of the optical signal on which the processing is executed by the processing section, by means of wavelength multiplexing and directs to the other end of the optical transmission line.Type: ApplicationFiled: April 5, 2010Publication date: October 21, 2010Applicant: Fujitsu LimitedInventors: Kyosuke Sone, Yutaka Kai, George Ishikawa, Susumu Kinoshita
-
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