Patent application number | Description | Published |
20090257115 | OPTICAL AMPLIFIER AND ABNORMALITY DETECTION METHOD FOR THE SAME - An optical amplifier includes a first optical amplification unit that amplifies input light, a variable optical attenuation unit that attenuates an output of the first optical amplification unit, a second optical amplification unit that amplifies an output of the variable optical attenuation unit, and a loss amount control unit that controls the variable optical attenuation unit, wherein an external attenuating optical medium is inserted between the variable optical attenuation unit and the second optical amplification unit. The optical amplifier includes an abnormality detecting unit that detects abnormality in optical loss based on a light level between the external attenuating optical medium and the second optical amplification unit, and a detection invalidating unit that invalidates any abnormality detected by the abnormality detecting unit when a light level between the variable optical attenuation unit and the external attenuating optical medium is lower than a threshold level. | 10-15-2009 |
20110026940 | OPTICAL COMMUNICATION DEVICE - An optical communication device using a digital coherent reception system includes a phase detector configured to generate, based on a signal obtained in a course of digital signal processing, a phase signal indicating a displacement of a sampling of a reception signal, a clock switch-determiner configured to switch from an reference clock to a clock of transferred data when a value of an amplitude of the phase signal exceeds a given threshold value, and a selector configured to synchronize the sampling of the reception signal and an internal clock of the digital signal processing with the reference clock at start time or signal loss time, and synchronize the sampling of the reception signal and the internal clock with the line clock of the reception signal except for the start time and the signal loss time. | 02-03-2011 |
20110200339 | OPTICAL RECEIVER - An optical receiver includes: a waveform distortion compensator to perform an operation on digital signal representing an optical signal generated by an A/D converter to compensate for waveform distortion of the optical signal; a phase detector to generate phase information representing sampling phase of the A/D converter; a phase adjuster to generate digital signal representing an optical signal in which the sampling phase of the A/D converter is adjusted from an output signal of the waveform distortion compensator using the phase information; a demodulator to generate a demodulated signal from the output signal of the phase adjuster; a phase controller to control the sampling phase of the A/D converter; a peak detector to detect a peak value of the phase information while the sampling phase of the A/D converter is controlled by the phase controller; and a compensation controller to control the waveform distortion compensator using the peak value. | 08-18-2011 |
20110229127 | DIGITAL COHERENT RECEIVER AND DIGITAL COHERENT RECEPTION METHOD - A digital coherent receiver converts signals and local light respectively detected, as detection results, in signal light from an optical transmission line, into digital signals and that further applies digital processing to the digital signals. The receiver includes a skew detecting unit that detects skew between the digital signals; a skew control unit controls the skew of each of the signals so that the skew to be detected by the skew detecting unit will be reduced; and a demodulating unit that demodulates each signal controlled for skew by the skew control unit. | 09-22-2011 |
20110229128 | OPTICAL NODE, OPTICAL NETWORK SYSTEM, AND METHOD FOR MEASURING POLARIZATION MODE DISPERSION - An optical node disposed along a transmission line that uses optical fiber. The optical node includes a first signal generator and a monitor. The first signal generator generates a first measurement signal for measuring polarization mode dispersion values and transmits the first measurement signal along the transmission line. The monitor detects a second measurement signal from the transmission line and measures polarization mode dispersion values by performing signal processing with respect to the second measurement signal. | 09-22-2011 |
20110255877 | DIGITAL COHERENT RECEIVER AND RECEIVING METHOD - A digital coherent receiver includes a front end, an A/D convertor, and a processor. The front end converts a light signal into an electric signal by using a signal light and a local oscillator light. The A/D convertor converts the electric signal of the front end into a digital signal. The processor calculates a spectrum gravity center of the digital signal converted by the A/D convertor, estimates a frequency offset of the digital signal based on the calculated spectrum gravity center, and reduces the frequency offset of the digital signal based on the estimated frequency offset. | 10-20-2011 |
20120087669 | OPTICAL NODE AND OPTICAL COMMUNICATION METHOD - In an optical node, a transmitter produces an optical supervisory signal for supervising an optical network, a processor is operative to control a power level of the optical supervisory signal according to a per-wavelength power level of an optical communication signal when the optical node has no post amplifiers, and a multiplexer combines the controlled optical supervisory signal with the optical communication signal to be transmitted to another optical node located downstream. | 04-12-2012 |
20120134684 | Adaptive equalizer, optical receiver, and tap coefficient correcting method - An adaptive equalizer includes a finite impulse response filter with a predetermined number of taps; and a tap coefficient adaptive controller having a register to hold tap coefficients for the filter, a weighted center calculator to calculate a weighted center of the tap coefficients, and a tap coefficient shifter to shift the tap coefficients based on a calculation result of the weighted center. During an initial training period, the tap coefficient shifter shifts the tap coefficients on a symbol data basis such that a difference between the calculated weighted center of the tap coefficients and a tap center defined by the number of taps is minimized. | 05-31-2012 |
20120148266 | DIGITAL COHERENT OPTICAL RECEIVER, ADAPTIVE EQUALIZER, AND DIGITAL COHERENT OPTICAL COMMUNICATION METHOD - A digital coherent optical receiver includes a processor that is operative to separate electric signals obtained by converting an optical signal into a horizontal signal component and a vertical signal component; to generate a histogram of the horizontal signal component and the vertical signal component as outputs of the equalizing filter; and to determine a presence/absence of local convergence based on distribution of the histogram of the horizontal signal component and the histogram of the vertical signal component. | 06-14-2012 |
20120308227 | DIGITAL COHERENT RECEIVER AND PHASE CONTROL METHOD - A digital coherent receiver includes a sampling phase detector to detect a phase of a sampled digital signal, and a phase adjustor to adjust the sampling phase of the digital signal based upon the detected phase. The phase detector includes filters to equalize the digital signal with different equalization characteristics; sensitivity monitoring phase detectors, each connected to one of the filters and outputting a phase detection signal representing the phase of the output signal from the associated filter together with a sensitivity monitoring signal representing the sensitivity of the phase detection; sensitivity correction coefficient generators, each generating a sensitivity correction coefficient for correcting the associated phase detection signal using a square sum of the sensitivity monitoring signals; and an adder to add the phase detection signals that have been corrected by the sensitivity correction coefficients, and output a phase signal. | 12-06-2012 |
20130259478 | OPTICAL TRANSMITTER, OPTICAL RECEIVER, AND OPTICAL TRANSMISSION METHOD - There is provided an optical transmitter including: a demultiplexer configured to divide a data frame of a transmission signal into subframes with a predetermined length so as to form the subframes in a plurality of signal lanes; an index generator configured to generate an index for indicating an order of the signal lanes; a lane rearrangement unit configured to rearrange the order of the signal lanes according to the index; a carrier controller configured to generate a frequency offset of a carrier corresponding to the index; a mapping unit configured to map the transmission signal in the plurality of signal lanes with the rearranged order to the transmission signal with a phase corresponding to the frequency offset; and a transmitting unit configured to optically modulate the mapped transmission signal so as to transmit the modulated transmission signal. | 10-03-2013 |
20140079385 | TRANSMITTING DEVICE, COMMUNICATION SYSTEM, AND METHOD FOR TRANSMISSION LEVEL CONTROL - A transmitting device includes a transmitter configured to transmit signal light to an external receiver over a medium included in a transmission line; and a controller configured to control a transmission level of the signal light in accordance with a reception level of probe light which is input from the receiver over the medium in the transmission line. | 03-20-2014 |
20140139906 | OPTICAL AMPLIFIER AND TRANSMISSION SYSTEM - An optical amplifier includes: a first amplifier amplifying a signal light by a first excitation light; a variable optical attenuator attenuating the signal light; a second amplifier amplifying the signal light by a second excitation light; a mode selector selecting one of first and second modes; a gain controller, in first mode, controlling first and second excitation lights so that a gain of power of the signal light becomes constant; a first output controller, in second mode, controlling the first excitation light; a second output controller that, in second mode, controlling the second excitation light so that a spontaneous emission light having fixed level is outputted; and an attenuation controller controlling an attenuation of the variable optical attenuator according to an input level of the signal light in first mode, and controlling the attenuation to become a given value larger than a value of first mode in second mode. | 05-22-2014 |
20140146385 | RAMAN AMPLIFIER - Raman amplifier includes: a pump-light generator configured to supply pump light to a transmission fiber; a measurement circuit configured to measure a relationship between power of the pump light and power of noise output from the transmission fiber with respect to a range from first pump-light power to second pump-light power; a signal detector configured to monitor a supervisory signal in output light of the transmission optical; and a decision unit configured to decide a state of the transmission fiber according to the monitoring result. When the supervisory signal is detected without the pump light, the measurement circuit measures the relationship while increasing the power of the pump light from the first pump-light power. When the supervisory signal is not detected without the pump light, the measurement circuit measures the relationship while decreasing the power of the pump light from the second pump-light power. | 05-29-2014 |
20140294378 | TRANSMISSION APPARATUS, TRANSMISSION SYSTEM, AND METHOD OF CONTROLLING AVERAGE OPTICAL INPUT POWER - A transmission apparatus includes: an amplifier controller configured to determine a target value for an average optical input power of a transmitting amplifier in a transmitting-side apparatus, based on an index based on a quality of transmission from an output of the transmitting amplifier to an output of a receiving amplifier in a receiving-side apparatus; and a pre-emphasis controller configured to determine amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the output of the receiving amplifier. | 10-02-2014 |