Patent application number | Description | Published |
20080239448 | OPTICAL MODULATION DEVICE AND OPTICAL MODULATION METHOD - 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. | 10-02-2008 |
20090034988 | Control apparatus and control method for optical modulator - 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. | 02-05-2009 |
20090047028 | QUADRATURE PHASE-SHIFT KEYING MODULATOR AND PHASE SHIFT AMOUNT CONTROLLING METHOD FOR THE SAME - 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. | 02-19-2009 |
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 |
20090142075 | DQPSK optical receiver - According to an aspect of an embodiment, a DQPSK optical receiver, comprising: a first LPF connected to a line branching off from between a first optical-electrical converter and a first data recovery circuit; a second LPF connected to a line branching off from between a second optical-electrical converter and a second data recovery circuit; a first LIA for amplifying a signal output from the first LPF and also limiting an amplitude of an output signal thereof; a second LIA for amplifying a signal output from the second LPF and also limiting an amplitude of an output signal thereof; a first mixer for multiplying the output signal from the first LIA by a signal output from the second LPF; and a second mixer for multiplying the output signal from the second LIA by a signal output from the first LPF. | 06-04-2009 |
20090148166 | Optical Add/Drop Multiplexer - 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. | 06-11-2009 |
20090244685 | Optical modulator and controlling method and apparatus thereof - 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 4 | 10-01-2009 |
20100067914 | Polarization multiplexed light transmitter and control method threof - 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. | 03-18-2010 |
20100080571 | OPTICAL SIGNAL TRANSMITTER - 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. | 04-01-2010 |
20100098435 | OPTICAL TRANSMITTER APPARATUS - 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. | 04-22-2010 |
20100254716 | Control apparatus and control method for optical modulator - 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. | 10-07-2010 |
20100254718 | OPTICAL RECEIVER AND METHOD FOR OPTICAL RECEPTION - 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. | 10-07-2010 |
20110026935 | OPTICAL SIGNAL TRANSMITTER AND METHOD FOR CONTROLLING POLARIZATION MULTIPLEXED OPTICAL SIGNAL - 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−Δφ and control the phase difference by the second phase shifter to A+Δφ; 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. | 02-03-2011 |
20110032594 | Optical modulation device and optical modulation method - 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. | 02-10-2011 |
20110038636 | Optical Add/Drop Multiplexer - 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. | 02-17-2011 |
20110044702 | POLARIZATION MULTIPLEXED OPTICAL TRANSMITTER AND METHOD FOR CONTROLLING POLARIZATION MULTIPLEXED OPTICAL SIGNAL - A polarization multiplexed optical transmitter includes first and second modulation units, combiner, phase controller, and signal controller. The first and second modulation units generate first and second modulated optical signals, respectively. The first and second modulation units include first and second phase shifter to give phase difference between optical paths of corresponding Mach-Zehnder interferometer, respectively. The combiner generates polarization multiplexed optical signal from the first and second modulated optical signals. The phase controller controls the phase difference by the first phase shifter to a target value and the phase difference by the second phase shifter to a value shifted by π from the target value. The signal controller controls operation state of at least one of the first and second modulation units based on optical intensity waveform of the polarization multiplexed optical signal. | 02-24-2011 |
20110170877 | OPTICAL TRANSMITTER APPARATUS - 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. | 07-14-2011 |
20110222853 | POLARIZED-WAVE-MULTIPLEXING OPTICAL TRANSMITTER AND CONTROL METHOD OF POLARIZED-WAVE-MULTIPLEXED OPTICAL SIGNAL - A polarized-wave-multiplexing optical transmitter including: an optical combiner generating a polarized-wave-multiplexed optical signal by polarized-wave-multiplexing a first optical modulation signal and a second optical modulation signal; an optical power fluctuation portion fluctuating optical power of the first optical modulation signal and the second optical modulation signal periodically; a total-optical-power detection portion detecting fluctuation amount of total optical power of the polarized-wave-multiplexed optical signal; and an optical power controller reducing an optical power difference between the first optical modulation signal and the second optical modulation signal based on detection result of the total-optical-power detection portion. | 09-15-2011 |
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 |
20120141145 | DQPSK OPTICAL RECEIVER - According to an aspect of an embodiment, a DQPSK optical receiver, comprising: a first LPF connected to a line branching off from between a first optical-electrical converter and a first data recovery circuit; a second LPF connected to a line branching off from between a second optical-electrical converter and a second data recovery circuit; a first LIA for amplifying a signal output from the first LPF and also limiting an amplitude of an output signal thereof; a second LIA for amplifying a signal output from the second LPF and also limiting an amplitude of an output signal thereof; a first mixer for multiplying the output signal from the first LIA by a signal output from the second LPF; and a second mixer for multiplying the output signal from the second LIA by a signal output from the first LPF. | 06-07-2012 |
20120148260 | OPTICAL TRANSMITTER AND OPTICAL TRANSMISSION METHOD - An optical transmitter includes: a digital signal processor to generate a drive signal from input data; a controller to control an amplitude or power of the drive signal according to information relating to the digital signal processing of the digital signal processor; and an optical modulator to modulate input light with the drive signal controlled by the controller to generate an optical signal. | 06-14-2012 |
20120308240 | OPTICAL TRANSMITTER, CONTROL METHOD FOR THE SAME, AND OPTICAL TRANSMISSION SYSTEM - An optical transmitter includes an optical modulator having first and second waveguides to modulate carrier light at each of the waveguides using a driving signal with 2*n intensity levels (n is an integer 1 or greater); and a phase shifter to cause a phase difference between a first optical signal and a second optical signal output from the first waveguide and the second waveguide, respectively. A photodetector converts a portion of a multilevel optical modulation signal acquired by combining the first optical signal and the second optical signals into an electrical signal. A monitor detects a change in an alternating current component in the detected modulation signal. A controller controls at least one of a first bias voltage and a second bias voltage being supplied to the first waveguide and the second waveguide, respectively, so as to increase the power value of the alternating current component. | 12-06-2012 |
20130202315 | OPTICAL TRANSMITTER AND METHOD FOR CONTROLLING BIAS FOR OPTICAL MODULATOR - An optical transmitter includes a signal generator configured to generate a drive signal from input data, an optical modulator configured to have a voltage-to-light-intensity characteristic in which intensity of output light changes in response to an applied voltage, and to generate a light signal that corresponds to the drive signal, a multiplier configured to multiply the drive signal and an electric signal that is obtained from the light signal; and a control section configured to control, based on output of the multiplier, a bias voltage for the optical modulator. | 08-08-2013 |
20130279913 | METHOD FOR CONTROLLING POLARIZATION MULTIPLEXED OPTICAL SIGNAL - 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−Δφ and control the phase difference by the second phase shifter to A+Δφ; 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. | 10-24-2013 |
20140140707 | OPTICAL TRANSMISSION DEVICE, METHOD OF OPTICAL TRANSMISSION, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM - An optical transmission device includes: a drive signal generate unit that generates a drive signal; a modulation unit that modulates an optical signal in accordance with the drive signal; a detect unit that detects a fluctuation of a signal component of the drive signal with respect to an optical signal output by the modulation unit; and a correct unit that corrects a parameter of the drive signal generate unit in accordance with a detect result of the detect unit so that a non-linear characteristic of the modulation unit gets closer to a linear characteristic. | 05-22-2014 |
20140212136 | OPTICAL TRANSMITTER AND MODULATED OPTICAL SIGNAL GENERATING METHOD - An optical transmitter includes: an optical modulator including a first modulation unit and a second modulation unit respectively configured to propagate a first optical signal and a second optical signal that are obtained by splitting input light; a signal generator configured to generate a first drive signal and a second drive signal that are respectively supplied to the first modulation unit and the second modulation unit; a phase controller configured to control a phase difference between the first optical signal and the second optical signal in the optical modulator; and a phase difference detector configured to detect the phase difference between the first optical signal and the second optical signal controlled by the phase controller. The signal generator generates the first drive signal and the second drive signal based on the phase difference detected by the phase difference detector. | 07-31-2014 |
20140334829 | OPTICAL TRANSMITTER AND BIAS CONTROL METHOD OF OPTICAL MODULATOR - An optical transmitter includes: a drive signal generator configured to generate a drive signal from input data; an optical modulator configured to generate an optical signal corresponding to the drive signal; a superimposer configured to superimpose a first reference signal on the drive signal and superimpose a second reference signal on a bias voltage of the optical modulator; a detector configured to detect the first reference signal and the second reference signal included in the optical signal, and generate a first monitor signal indicating intensity and a phase of the detected first reference signal and a second monitor signal indicating intensity and a phase of the detected second reference signal; and a controller configured to control the bias voltage of the optical modulator in a control scheme determined based on the first monitor signal and the second monitor signal. | 11-13-2014 |