Patent application number | Description | Published |
20080240737 | OPTICAL RECEIVER AND CONTROL METHOD FOR OPTICAL RECEIVER - An optical receiver converting an optical signal modulated by differential phase shift keying to electrical first and second data signals; generating a clock signal from the first data signal; demultiplexing the first data signal into two signals; latching the two signals using the clock signal; delaying the clock signal by a certain amount; latching the two signals using the delayed clock signal; demultiplexing the second data signal into two additional signals; generating an inverted clock signal by inverting the clock signal; latching the two additional signals using the inverted clock signal or the clock signal; and further latching the two additional signals using the delayed clock signal. | 10-02-2008 |
20080297270 | Driver circuit of optical modulator - A drive signal generation unit generates first and second drive signals for driving first and second phase modulators of a DQPSK optical modulator. First and second regeneration circuits regenerate the first and second drive signals with respect to clock signals. The first and second phase modulators are driven by the regenerated first and second drive signals. The amplitude of the first drive signal is adjusted by a first attenuator. The clock signal for the second regeneration circuit is applied after attenuated by a second attenuator. The delay time caused by the first attenuator is the same as the delay time caused by the second attenuator. | 12-04-2008 |
20090041473 | Optical device, optical modulation method, and optical transmitter - An optical modulation device including waveform shapers that waveform-shape input data signals in synchronism with a rising or falling timing based on comparison with a reference level of an input clock signal, a multi-level phase modulator that generates a multi-level-phase-modulated optical signal based on the data signals waveform-shaped by the plurality of waveform shapers, and outputs the generated optical signal, and a level ratio controller that varies a relative level ratio of the reference level to an amplitude level of the clock signal input to the waveform shapers, based on the optical signal output from the multi-level phase modulator. | 02-12-2009 |
20090080894 | Chromatic dispersion compensating apparatus - In order to compensate for chromatic dispersion ad dispersion slope over an entire wavelength band of the optical signal, the wavelength band is split into a plurality of bands, and chromatic dispersion compensation is made to make chromatic dispersion in a central wavelength of each of the bands zero. | 03-26-2009 |
20090116844 | Electrical-dispersion compensating apparatus, optical receiving apparatus, and optical receiving method - An optical receiving apparatus branches an optical signal, photo-electric-converts the branched signals, and compensates dispersion in each of the converted electrical signals. Electrical-dispersion compensators respectively compensate the dispersion in the electrical signals using a transversal filter having plural taps. A dispersion control unit controls the dispersion compensation amount for each of the electrical signals by adjusting tap coefficients of the transversal filter. A delay control unit controls the difference in the delay time of the electrical signals by adjusting the tap coefficients adjusted by the dispersion control unit. An identifying circuit identifies data in the optical signal based on each of the electrical signals that have been subjected to dispersion compensation by each of the electrical-dispersion compensators. | 05-07-2009 |
20090279895 | Frequency doubler, signal generator, optical transmitter, and optical communication apparatus - An input unit receives input of a clock signal having a voltage that varies continuously. A supply unit supplies a constant reference voltage. A selector outputs a clock signal having voltage that is changed alternately each time the voltage of the clock signal input from the input unit shifts across the reference voltage supplied from the supply unit. A calculating circuit outputs the exclusive-OR of the clock signal input from the input unit and a clock signal output from the selector. | 11-12-2009 |
20100054756 | Optical modulator and optical transmitter using the same - In an optical modulator, a DQPSK modulating section, a waveguide optical amplifying section, and an RZ modulating section are cascade connected on an optical path between input and output ports, and power of RZ-DQPSK signal light output from the output port is monitored by a photodetector, to feed-back control the waveguide optical amplifying section by an output control section so that the monitored power becomes constant at a target level. As a result, a small and low-cost optical modulator that can reliably compensate respective losses in a phase modulating section and an intensity modulating section, and differences of the respective losses, can be realized. | 03-04-2010 |
20100092186 | OPTICAL RECEIVER AND LIGHT RECEIVING METHOD - An apparatus and method includes converting an optical signal that is received into an electrical signal and outputting the electrical signal, converting the electrical signal into a data signal and outputting the data signal by comparing the electrical signal with a reference voltage, monitoring the electrical signal and output monitored information, and controlling the reference voltage based on the monitored information. | 04-15-2010 |
20100135664 | Chromatic dispersion compensating apparatus - In order to compensate for chromatic dispersion ad dispersion slope over an entire wavelength band of the optical signal, the wavelength band is split into a plurality of bands, and chromatic dispersion compensation is made to make chromatic dispersion in a central wavelength of each of the bands zero. | 06-03-2010 |
20100178065 | DELAY PROCESSING APPARATUS, SIGNAL AMPLIFICATION APPARATUS, OPTO-ELECTRIC CONVERSION APPARATUS, ANALOG-DIGITAL CONVERSION APPARATUS, RECEIVING APPARATUS, AND RECEIVING METHOD - A delay device that provides a delay amount to at least one of the in-phase signal and the quadrature signal, and a delay control section that controls the delay amount provided by the delay device based on a quality of the signals when the in-phase signal and the quadrature signal, to the at least one of which the delay amount is provided, at the delay device are converted into digital signals by the analog-digital converter, and the digital signal processing is carried out at the processor are provided. Thereby, the signal quality of recovered data at a receiving end of a multi-level phase modulation communication system is improved. | 07-15-2010 |
20100260504 | OPTICAL TRANSMISSION SYSTEM - An optical transmission system includes an optical transmitter that includes first and second light sources, first and second phase modulators respectively modulating light from the first and the second light sources, and a polarized beam combiner combining the light output from the first and the second phase modulators to output an optical signal; and an optical receiver that includes a local oscillator, a polarization beam splitter splitting, according to polarization, the optical signal transmitted from the optical transmitter, and first and second digital coherent receivers corresponding to the first and the second phase modulators, and including a frontend that mixes light from the local oscillator and the polarization-split optical signal to output an electrical signal of real and imaginary parts, an analog-digital converting unit converting the electrical signal to a digital signal, and a digital signal processing unit estimating phase of the digital signal and extracting a signal. | 10-14-2010 |
20110150506 | OPTICAL RECEIVER AND RECEIVING METHOD - An optical receiver includes an optical front-end, a digital converter, a frequency-characteristic-difference reducing unit and an identifying unit. The optical front-end splits an input signal light into signal light components on a basis of local light and converts the split signal light components into electrical signals. The digital converter converts the electrical signals, converted by the optical front end, into digital signals. The frequency-characteristic-difference reducing unit reduces a frequency-characteristic difference between the digital signals converted by the digital converter. The identifying unit identifies each of the digital signals whose frequency-characteristic difference is reduced by the frequency-characteristic-difference reducing unit. | 06-23-2011 |
20110229148 | OPTICAL MODULATION APPARATUS AND OPTICAL MODULATION METHOD - An optical modulation apparatus includes a first modulator, a second modulator, a multiplexer, a detector and an adjustor. The first modulator modulates light emitted by a light source using a first input signal and outputs a first modulated signal. The second modulator modulates the light using a second input signal and outputs a second modulated signal. The multiplexer multiplexes the first and second modulated signals and outputs a multiplexed signal. The detector is configured to detect a dip where power in a waveform of the multiplexed signal is equal to or smaller than a predetermined value. The adjustor is configured to adjust a delay of the first and second input signals based on power at the dip. | 09-22-2011 |
20110229150 | OPTICAL MODULATION APPARATUS AND OPTICAL MODULATION METHOD - An optical modulation apparatus includes a first modulator, a second modulator, a multiplexer, a calculator and an adjustor. The first modulator configured to modulate light emitted by a light source using a first input signal and output a first modulated signal. The second modulator configured to modulate the light using a second input signal and output a second modulated signal. The multiplexer configured to multiplex the first and second modulated signals and output a multiplexed signal. The calculator configured to calculate a power difference between a higher-side frequency component having a frequency higher than a center frequency of the multiplexed signal and a lower-side frequency component having a frequency lower than the center frequency. The adjustor configured to adjust delays of the first and second input signals based on the power. | 09-22-2011 |
20110293276 | OPTICAL TRANSMITTER AND METHOD FOR CONTROLLING THE SAME - An optical transmitter includes: a first modulator that modulates a first optical signal with a first data signal; a second modulator that modulates a second optical signal with a second data signal; a multiplexer that multiplexes the first optical signal and the modulated second optical signal to output a multiplexed signal; a phase difference data generator that generates a phase difference signal corresponding to a phase difference between the modulated first optical signal and the modulated second optical signal from the multiplexed signal; and a controller that controls the phase difference between the modulated first optical signal and the modulated second optical signal based on the phase difference signal. | 12-01-2011 |
20120082465 | OPTICAL TRANSMITTING APPARATUS, OPTICAL RECEIVING APPARATUS, AND OPTICAL COMMUNICATION SYSTEM COMPRISING THEM - A phase shift unit provides a prescribed phase difference (π/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal f | 04-05-2012 |
20120148235 | CONTROL CIRCUIT, COMMUNICATION SYSTEM, AND CONTROL METHOD - A communication system includes a transmitter, a receiver device, and a control circuit. The transmitter transmits an optical signal. The receiver device receives the optical signal. The control circuit reduces a power consumption of the receiver device based on an accumulated chromatic dispersion of the received optical signal. The receiver device includes a receiver, an analog/digital converter, and a digital signal processor. The receiver extracts a signal indicating a complex amplitude of the optical signal. The analog/digital converter converts the signal indicating the complex amplitude into a digital signal. The digital signal processor digitally-processes the digital signal. | 06-14-2012 |
20120155883 | OPTICAL RECEIVER AND OPTICAL RECEIVING METHOD - An optical receiver includes an analog/digital converter, and a control circuit. The analog/digital converter has a dynamic range at a time of converting an analog electric signal generated based on an optical signal to a digital electric signal. The dynamic range is variable, and the control circuit varies the dynamic range of the analog/digital converter based on the chromatic dispersion of the optical signal. | 06-21-2012 |
20120230694 | OPTICAL TRANSMITTER - A clock signal from a single reference clock is frequency converted, and the frequency-converted signal is input to an equal-interval-optical-frequency-comb generator and a modulator of an optical modulator. By varying the electric frequency of the clock signal input to the equal-interval-optical-frequency-comb generator, frequency intervals of a frequency comb to be generated can be varied, while by selectively employing a particular optical frequency from among the continuous light beams of the generated frequency comb, a frequency comb having unequal intervals can be generated. It is also possible to vary the modulation rate by varying the clock frequency of a driving signal to be input to the optical modulator. By using a clock signal of a single reference clock, the frequency intervals of the frequency comb and the variation of the modulation rate synchronize with each other. | 09-13-2012 |
20120237212 | OPTICAL NETWORK SYSTEM - There is provided an optical network system in which optical signals modulated by each of at least two modulation methods are wavelength-division-multiplexed and transferred, including: an optical transmitter configured to transmit first optical signals modulated by each of at least two modulation methods; an add-drop multiplexer configured to drop second optical signals from wavelength-division-multiplexed optical signals transferred in the optical network system, and add the first optical signals to the wavelength-division-multiplexed optical signals; an optical receiver configured to demodulate the second optical signals corresponding to each of at least two modulation methods; and a controller configured to control wavelengths of the first optical signals, the second optical signals and the wavelength-division-multiplexed optical signals so as to rearrange wavelengths of the first optical signals, the second optical signals and the wavelength-division-multiplexed optical signals so that optical signals modulated by a same modulation method are placed on an adjacent wavelength. | 09-20-2012 |
20120243880 | MULTI-WAVELENGTH LIGHT SOURCE - Light output from a seed light source generation unit that outputs continuous light having a single frequency or a plurality of frequencies is input by a multi-wavelength light source to an optical circulation unit, and light having a plurality of frequencies that is frequency-synchronized with seed light output from the seed light source generation unit is generated. The optical circulation unit is provided with an optical frequency shifter to shift light frequencies, and includes a circulation circuit to return output from the optical frequency shifter to the input side. On a circulation path, an optical spectral shaper capable of adjusting an optical amount of attenuation for each frequency unit is provided so that optical amount of attenuations are adjusted, and thereby the number and the like of optical frequencies output from the optical circulation unit are changed. | 09-27-2012 |
20140099111 | PON SYSTEM AND SUBCARRIER ASSIGNING METHOD - A PON (Passive Optical Network) system, which modulates multiple subcarriers with data of multiple users to output an optical multiplexed signal from a station device, splits the optical multiplexed signal to transmit the split signals to multiple subscriber devices that are provided for each of the users, and demodulates the data of the users at the respective subscriber devices, includes: an obtaining section configured to obtain a transmission characteristic for each of the subcarriers at each of the subscriber devices, by receiving a test signal at the subscriber devices, which is transmitted from the station device; and an assigning section configured to assign one or more of the subcarriers for each of the subscriber devices suited to the transmission characteristics of the assigned subcarriers at each of the subscriber devices. | 04-10-2014 |
20140099114 | OPTICAL SIGNAL TRANSMITTING APPARATUS, OPTICAL FREQUENCY DIVISION MULTIPLEX TRANSMISSION SYSTEM, AND OPTICAL SIGNAL COMMUNICATION METHOD - An optical signal transmitting apparatus is disposed in an optical frequency division multiplex transmission system that includes plural nodes that are in an optical transmission path and respectively use a unique frequency to frequency-multiplex information with a carrier wave to transmit the information to an optical signal receiving apparatus in the optical transmission path. The optical signal transmitting apparatus outputs the carrier wave and includes a transmitting unit into which information to be delivered to the nodes is input, the transmitting unit transmitting the information using a frequency that does not overlap the unique frequencies used by the nodes; and a multiplexing unit that frequency-multiplexes output of the transmitting unit and the carrier wave, and sends the frequency-multiplexed output to the optical transmission path. | 04-10-2014 |
20140099115 | TRANSMITTING APPARATUS, RECEIVING APPARATUS, OPTICAL FREQUENCY DIVISION MULTIPLEX TRANSMISSION SYSTEM, AND OPTICAL SIGNAL COMMUNICATION METHOD - A transmitting apparatus is used in an electrical frequency division multiplex transmission system including nodes that are on an optical transmission path and that respectively frequency-multiplex a sub-carrier of a unique frequency and a carrier wave to transmit information to a receiving apparatus on the optical transmission path. The transmitting apparatus is disposed in each node and includes a determining unit that receives an input of information concerning unused sub-carriers of a transmission signal in the optical transmission path and determines transmission of the information to the receiving apparatus using an unused sub-carrier; an electrical frequency division multiplex transmission unit that using a frequency of the unused sub-carrier determined by the determining unit, modulates the input information to be transmitted to the receiving apparatus; and a coupling unit that adds to the transmission signal in the optical transmission path, a modulated modulation signal. | 04-10-2014 |
20140153925 | TRANSMISSION CONTROL DEVICE, TRANSMISSION SYSTEM, AND TRANSMISSION METHOD - A transmission control device includes a subcarrier selector configured to select one or more subcarriers for transmitting an error correction code for correcting data, from a plurality of subcarriers having different transmission capacities, each of the plurality of subcarriers used for transmitting either of the data and the error correction code, in accordance with an amount of data of the error correction code and transmission capacities respectively assigned to the plurality of subcarriers. | 06-05-2014 |
20140369677 | OPTICAL TRANSMITTER AND OPTICAL TRANSMISSION METHOD - An optical transmitter converts a plurality of transmission signals transmitted via a plurality of lanes into a multi-carrier signal and transmits the multi-carrier signal. The optical transmitter includes: a controller configured to generate allocation information that indicates an allocation of sub-carriers to the plurality of lanes according to a bit rate of the transmission signal of each of the lanes and a possible transmission capacity of each of the sub-carriers; and a signal processor configured to convert the plurality of transmission signals into the multi-carrier signal in accordance with the allocation information generated by the controller. | 12-18-2014 |
20150071642 | OPTICAL TRANSMITTER, OPTICAL RECEIVER, OPTICAL TRANSMISSION SYSTEM, OPTICAL TRANSMITTING METHOD, OPTICAL RECEIVING METHOD AND OPTICAL TRANSMISSION METHOD - An optical transmitter includes: a digital signal process unit that generates a drive signal for generating multi-carrier signals through a plurality of independent digital signal processes, the multi-carrier signals having a cyclic prefix and to be transmitted by a parallel transmission; a synchronization unit that synchronizes clocks of the plurality of digital signal processes; and an adjust unit that reduces a delay difference of the cyclic prefix between the multi-carrier signals after the parallel transmission. | 03-12-2015 |