# Zhenning Tao, Beijing CN

## Zhenning Tao, Beijing CN

Patent application number | Description | Published |
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20080205905 | DIGITAL PHASE ESTIMATOR, DIGITAL PHASE LOCKED LOOP AND OPTICAL COHERENT RECEIVER - The present invention provides a digital phase estimator, a digital phase locked loop and an optical coherent receiver. The optical coherent receiver comprises a local oscillator laser, for supplying a local oscillator optical signal; an optical 90 degree frequency mixer, for mixing a received optical signal with the local oscillator optical signal; first and second balancing photoelectric detectors, for converting the optical signals outputted from the optical 90 degree frequency mixer into baseband electrical signals; first and second A/D converters, for respectively converting output signals from the first and the second balancing photoelectric detectors into digital signals; a digital phase locked loop, for compensating a phase difference between a carrier signal of the received optical signal and the local oscillator optical signal, and outputting the compensated signal; and a data recovering unit, for recovering data from the compensated signal. | 08-28-2008 |

20090034967 | PHASE MONITOR APPARATUS, PHASE CONTROL APPARATUS AND METHODS THEREOF FOR OPTICAL DQPSK RECEIVER - I branch is provided with a first interferometer, a first balanced optical detector, and a first data recovery circuit. Q branch is provided with a second interferometer, a second balanced optical detector and a second data recovery circuit. In I branch, a mixer multiples input signal of the first data recovery circuit with output signal of the second recovery circuit. An averaging circuit averages output signal of the mixer. In Q branch, a mixer multiples input signal of the second data recovery circuit with output signal of the first recovery circuit. An averaging circuit averages output signal of the mixer. A first phase control apparatus controls the phase of a phase shifter comprised in the first interferometer based on the output signal of the averaging circuit. A second phase control apparatus, in the same manner, controls the phase of a phase shifter comprised in the second interferometer. | 02-05-2009 |

20090080906 | Frequency offset monitoring device and optical coherent receiver - The present invention provides a frequency offset monitoring device and an optical coherent receiver. A low speed frequency offset monitoring device comprises a signal speed lowering section, for lowering the speed of an inputted signal and outputting the speed lowered signal, and a frequency offset monitor, for monitoring frequency offset of the speed lowered signal outputted by the signal speed lowering section. | 03-26-2009 |

20090129787 | Optical coherent receiver, frequency offset estimating apparatus and method for optical coherent receiver - The present invention discloses an optical coherent receiver, and a frequency offset estimating apparatus and a frequency offset estimating method for use in the optical coherent receiver. The optical coherent receiver includes a front end processing section for changing an optical signal into a base band digital electric signal. The frequency offset estimating apparatus comprises a phase offset calculating section, for calculating a phase offset in said base band digital electric signal; a phase offset change calculating section, for calculating a change of said phase offset, namely a phase offset change, in accordance with the phase offset calculated by said phase offset calculating section; an ambiguity deciding section, for deciding whether there is ambiguity in said phase offset change calculated by said phase offset change calculating section, and outputting the phase offset change having no ambiguity; and a loop filtering section, for acquiring a weighted average of the phase offset change outputted by said ambiguity deciding section. | 05-21-2009 |

20090141831 | Phase error estimator, coherent receiver and phase error estimating method - The present invention relates to a phase error estimator, a coherent receiver and a phase error estimating method. The phase error estimator estimates a phase error in an inputted base band electric signal and feeds back said phase error; said phase error estimator comprises: a pre-decider, for judging a phase of data in said base band electric signal in accordance with said feedback phase error; a phase error complex value extracting section, for extracting a real part and an imaginary part of the phase error in accordance with the judgment result of said pre-decider; a phase error determining section, for determining said phase error in accordance with the real part and the imaginary part of the phase error extracted by the phase error complex value extracting section; and a time delay feeding back section, for delaying said phase error by N number of symbols and feeding back the delayed phase error to said pre-decider, wherein N is an integer greater than 1. | 06-04-2009 |

20090142076 | Frequency offset compensating apparatus and method, and optical coherent receiver - The present invention relates to a frequency offset compensating apparatus and method, and an optical coherent receiver. The optical coherent receiver includes a front end processor and a frequency offset estimator, of which said front end processor converts an inputted optical signal into a base band digital electric signal, and said frequency offset estimator estimates a phase offset change introduced by a frequency offset in said base band digital electric signal; said frequency offset compensating apparatus comprises an M output integrator, for integrating the phase offset change introduced by the frequency offset to acquire M inverse numbers of the phase offset introduced by the frequency offset, where M is an integer greater than 1; a series-parallel converting device, for dividing said base band digital electric signal into M sub base band digital electric signals; M complex multipliers, for constructing the corresponding inverse numbers in the M inverse numbers to be complex numbers, and multiplying them with the corresponding sub base band digital electric signals in the M sub base band digital electric signals; and a parallel-series converting device, for converting the M sub base band digital electric signals multiplied by said complex multipliers into a base band electric signal. | 06-04-2009 |

20090245815 | Apparatus and method for frequency offset monitoring used in digital coherent optical receiver - The present invention discloses a frequency offset detecting apparatus and method for use in a digital coherent optical receiver. The digital coherent optical receiver comprises: a front-end processing section for generating a digital baseband electric signal; an equalizer for performing equalized filtering on the digital baseband electric signal; and the frequency offset detecting apparatus for detecting frequency offset contained in the digital baseband electric signal or frequency offset contained in a signal outputted by the equalizer; wherein the frequency offset detecting apparatus comprises an argument difference obtaining unit, a first subtracter, a second subtracter, a quantizer and an averager, of which the argument difference obtaining unit obtains an argument difference of adjacent symbols in a signal inputted therein; the first subtracter subtracts an output of the averager from the argument difference obtained by the argument difference obtaining unit; the quantizer performs uniform quantization with predetermined intervals on an output of the first subtracter; the second subtracter subtracts an output of the quantizer from the argument difference obtained by the argument difference obtaining unit; and the averager averages an output of the second subtracter. | 10-01-2009 |

20090245816 | Filter coefficient changing apparatus and method - The present invention discloses filter coefficient changing apparatus and method for use in a dual-polarized optical coherent receiver. The apparatus comprises a controlling unit, a switching unit and a new coefficient obtaining unit. The switching unit is connected between a first filter coefficient updating unit and a first filtering unit and a second filtering unit; the new coefficient obtaining unit generates new filter coefficients for the first filtering unit and the second filtering unit in accordance with filter coefficients outputted by a second filter coefficient updating unit; and the controlling unit generates a control signal that controls switching of the switching unit. Upon reception of the control signal, the switching unit breaks off output of the filter coefficients from the first filter coefficient updating unit, transmits new filter coefficients from the new coefficient obtaining unit to the first filtering unit and the second filtering unit, and subsequently resumes the output of the filter coefficients from the first filter coefficient updating unit to the first filtering unit and the second filtering unit. | 10-01-2009 |

20090304064 | ADAPTIVE EQUALIZER AND METHOD THEREOF - The present invention relates to an adaptive equalizer and an adaptive equalizing method. The adaptive equalizer comprises an adaptive equalizing unit, for adaptively equalizing an inputted signal to output the equalized signal; a coefficient updating unit, for updating a coefficient of a filter of the adaptive equalizing unit; a switching unit, connected between the coefficient updating unit and the adaptive equalizing unit, wherein when the switching unit is on, the coefficient updating unit is capable of updating the coefficient of the adaptive equalizing unit, and when the switching unit is off, the coefficient updating unit is incapable of updating the coefficient of the adaptive equalizing unit; and a monitoring device, for controlling on or off of the switching unit in accordance with a down sampling phase of the inputted signal or a down sampling phase of the equalized signal. | 12-10-2009 |

20100002810 | ADAPTIVE OPTIMIZATION METHOD AND APPARATUS FOR AVERAGE LENGTH - The invention provides an average length adaptive optimization method and apparatus. An adaptive optimization method for the average length used for phase recovery comprising: a residual phase difference calculation step, for receiving a current phase of a digital symbol obtained by phase recovery and a data modulation phase of the digital symbol obtained by data recovery, and calculating a residual phase difference of the digital symbol, which is a difference between the current phase and the data modulation phase of the digital symbol; a residual phase difference auto-correlation value calculation step, for calculating an auto-correlation value of the residual phase difference with displacement m, wherein −10≦m≦10, and m is an integral; an optimization step, for optimizing the average length based on the residual phase difference auto-correlation value. | 01-07-2010 |

20100003028 | FILTER COEFFICIENT ADJUSTMENT APPARATUS - In present invention, a filter coefficient adjustment apparatus is used in a polarization demultiplexer which demultiplexes the input signals by using filters to obtain demultiplexed output signals, said filter coefficient adjustment apparatus being used for adjusting the coefficients of the filters, wherein said filter coefficient adjustment apparatus comprises: an logarithm partial derivative calculation unit for calculating the logarithm partial derivative value of a target probability density function of the demultiplexed output signals when its self-variable value is the present demultiplexed output signal value; a gradient calculation unit for calculating the gradient of a target optimizing function for optimizing the distribution of the multiplexed output signals based on the logarithm partial derivative value calculated by the logarithm partial derivative calculation unit; and a filter coefficient updating unit for updating the coefficients of the filters based on the gradient calculated by the gradient calculation unit. | 01-07-2010 |

20100092168 | OPTICAL COHERENT RECEIVER, APPARATUS FOR AND METHOD OF MONITORING PERFORMANCE THEREOF - The present invention relates to an optical coherent receiver and an apparatus for and a method of monitoring performance thereof. The apparatus for monitoring performance of the optical coherent receiver makes use of a first signal and a second signal from the optical coherent receiver to monitor performance of the optical coherent receiver, and comprises a first subtracter, for subtracting the second signal from the first signal to obtain a first subtraction result; a squarer, for obtaining a square of the first subtraction result; a delayer, for delaying the first subtraction result; a multiplier, for multiplying the first subtraction result with the delayed first subtraction result; and a second subtracter, for subtracting the result of the multiplier from the result of the squarer. | 04-15-2010 |

20100142946 | CHROMATIC DISPERSION MONITOR AND METHOD, CHROMATIC DISPERSION COMPENSATOR - The present invention relates to chromatic dispersion monitor and method, chromatic dispersion compensator. The chromatic dispersion monitor is used for estimating a chromatic dispersion in accordance with a chromatic dispersion correlation amount sequence, comprising: a phase differential unit, for obtaining a phase difference sequence by performing a phase differential calculation in accordance with the chromatic dispersion correlation amount sequence; a phase difference differential unit, for obtaining a phase difference differential sequence by performing a phase difference differential operation; and a chromatic dispersion estimating unit, for estimating the chromatic dispersion in accordance with the phase difference differential sequence obtained by the phase difference differential unit. | 06-10-2010 |

20110064169 | FILTER COEFFICIENT CONTROL APPARATUS AND METHOD - This invention relates to an apparatus and a method for controlling a filter coefficient. The filter coefficient control apparatus controls a coefficient of a filter of a phase recovering apparatus, and comprises a phase offset obtaining means, for obtaining a phase offset between a carrier and a local oscillation; an autocorrelation calculating means, for calculating an autocorrelation and related statistics of the phase offset; and a filter coefficient determining means, for determining the coefficient of the filter in accordance with the autocorrelation and related statistics. | 03-17-2011 |

20110064421 | APPARATUS AND METHOD FOR EQUALIZING CHROMATIC DISPERSION AND DIGITAL COHERENT OPTICAL RECEIVER - This application relates to an apparatus and a method for equalizing chromatic dispersion and a digital coherent optical receiver. The apparatus for equalizing chromatic dispersion comprising: a chromatic dispersion equalizing unit, for compensating chromatic dispersion of an input signal; and an additional time delay removing unit, for removing, in accordance with frequency offset of the input signal, chromatic dispersion equalization time delay generated by the chromatic dispersion equalizing unit. | 03-17-2011 |

20110116809 | PHASE RECOVERY DEVICE, PHASE COVERY METHOD AND RECEIVER FOR 16 QAM DATA MODULATION - The present invention relates to a phase recovery device, phase recovery method and receiver for 16 QAM data modulation. The phase recovery device comprises: a fourth power calculator for calculating fourth power values of respective symbols in a symbol block; a classification unit for classifying respective symbols in the symbol block based on amplitudes, so as to classify respective symbols in the symbol block into a first category having a large or small amplitude, and a second category having an intermediate amplitude; a reference point determination unit for determining a reference point based on categories of respective symbols in the symbol block and their fourth power values; a rotation unit for rotating respective symbols in the symbol block undergone the fourth power operations and being classified into the second category, based on the reference point; and a phase estimation unit for performing phase estimations based on respective symbols in the symbol block undergone the fourth power operations and being classified into the first category, and respective rotated symbols in the symbol block undergone the fourth power operations and being classified into the second category. | 05-19-2011 |

20110129232 | EXTERNAL MODULATOR MONITORING DEVICE AND EXTERNAL MODULATOR MONITORING METHOD - This invention relates to external modulator monitoring device and method for monitoring an external modulator. The external modulator monitoring device includes a mixing unit for mixing optical signals modulated by the external modulator and optical signals not modulated by the external modulator, so as to obtain multiple branches of mixed optical signals; an electrical differential unit for converting the multiple branches of mixed optical signals into corresponding multiple branches of electrical signals, and performing a differential processing on voltages of the multiple branches of electrical signals to obtain differential signals; and a power detection unit for detecting power of the differential signals. | 06-02-2011 |

20110142455 | CROSSTALK COEFFICIENT ESTIMATING APPARATUS AND CROSSTALK COEFFICIENT ESTIMATING METHOD - This invention relates to crosstalk coefficient estimating apparatus and crosstalk coefficient estimating method. The crosstalk coefficient estimating apparatus is used to estimate a crosstalk coefficient of crosstalk inflicted on one channel of an optical fiber transmission system comprising two or more channels. The crosstalk coefficient estimating apparatus comprises a complex conjugate unit, for obtaining a complex conjugate signal for signal in one polarization-state of another channel other than said one channel; a multiplying unit, for multiplying the complex conjugate signal obtained by the complex conjugate unit with signal in another polarization-state of the another channel; and a filter, for filtering the multiplication result of the multiplying unit to obtain a crosstalk coefficient of crosstalk inflicted on the signal in one polarization-state of said one channel, wherein a transmission function of the filter is set according to system parameters of the optical fiber transmission system. | 06-16-2011 |

20110166846 | SIMULATION DEVICE AND SIMULATION METHOD - The present invention relates to a simulation device and simulation method for a cascade communication system. The cascade communication system comprises a plurality of nodes numbered as 1 to N successively from a transmitter to a receiver, the method comprises: acquiring simulation parameters required for simulating the cascade communication system; calculating reverse transfer functions of the respective nodes; determining a current node in a sequence from the Nth node to the first node; adding noise that should be added at the current node to a simulation signal of a previous node from the current node; simulating the current node to generate a simulation signal of the current node, by using the simulation signal of the previous node added with the noise that should be added at the current node, based on the reverse transfer function of the current node; judging whether simulations of all the nodes are completed; if the simulations of all the nodes are not completed, repeating the adding and the simulating for the simulation signal of the current node; if the simulations of all the nodes are completed, determining a cost of the cascade communication system based on the simulation signal of the current node. | 07-07-2011 |

20110243561 | FILTER, COHERENT RECEIVER DEVICE AND COHERENT RECEIVING METHOD - The present invention relates to filter, coherent receiver device and coherent receiving method. The filter is used for converting a partial response signal into a full response signal, wherein the filter uses the following transfer function H | 10-06-2011 |

20110243575 | METHOD FOR ADAPTIVE BLIND EQUALIZATION OF PSK SIGNAL, EQUALIZER AND RECEIVER - The present application discloses a method for adaptive blind equalization of a PSK signal, an equalizer and a receiver. According to embodiments as provided, a conjugate product of a current output and a precedent output of an FIR filter is calculated, an equalization coefficient is updated using the conjugate product, and then an input signal is filtered using the FIR filter with the updated equalization coefficient. The embodiments as provided is applicable to adaptive blind equalization of any phase shift keying signal including a BPSK signal. | 10-06-2011 |

20110286741 | APPARATUS AND METHOD FOR MONITORING STATISTICAL CHARACTERISTICS OF PHASE NOISES, AND COHERENT OPTICAL COMMUNICATION RECEIVER - This invention relates to an apparatus and a method for monitoring statistical characteristics of phase noises, as well as to a coherent optical communication receiver. The apparatus for monitoring statistical characteristics of phase noises comprises an argument calculating unit ( | 11-24-2011 |

20120026860 | APPARATUS AND METHOD FOR CROSS PHASE MODULATION RECOVERY - Apparatus and method for cross phase modulation recovery are disclosed. An apparatus for cross phase modulation recovery may include M stages of cross phase modulation recovering devices connected in cascade, wherein M≧2, and each stage of the M-stages of cross phase modulation recovering devices is configured to perform cross phase modulation recovery to a polarization de-multiplexed signal input into the each stage. An optical coherent receiver including such an apparatus for cross phase modulation recovery is also disclosed. | 02-02-2012 |

20120076235 | NONLINEAR COMPENSATING APPARATUS AND TRANSMITTER - The present invention provides nonlinear compensating apparatus and transmitter. The nonlinear compensating apparatus comprises: an information acquiring unit to acquire a symbol information sequence of the pulse information input by a transmitting side; a perturbation quantity calculating unit to calculate the weighted sum of the interaction of the pulses of several items at several different instants relative to the current instant, to obtain the perturbation quantity produced by the current instant nonlinear effect on a transmission link of a certain length; and an information compensating unit to compensate for the symbol information sequence of the pulses at the current instant acquired by the information acquiring unit by using the perturbation quantity obtained by the perturbation quantity calculating unit, so as to obtain the symbol information sequence compensated at the current instant to cause the transmitting side to transmit signals according to the compensated symbol information sequence. The apparatus corrects the symbol information sequence of the pulse signals input by a transmitting side, with the complexity of calculation being low, and the apparatus is applicable to single-polarization and dual-polarization multiplexing systems, and at the same time, compatible with any modulation format. | 03-29-2012 |

20120076491 | AVERAGE LENGTH MAGNITUDE DETECTING APPARATUS, AND METHOD - The present invention relates to an average length magnitude detecting apparatus and method, and an optical coherent receiver. The average length magnitude detecting method is adopted for detecting whether an average length of an averager used by a polarization crosstalk canceling apparatus in a receiver is long or short, comprising: determining a magnitude of a residual polarization crosstalk coefficient of the receiver; and determining an index that indicates whether the average length of the averager is long or short according to the determined magnitude of the residual polarization crosstalk coefficient. | 03-29-2012 |

20120269247 | MULTI-STAGE PHASE ESTIMATION METHOD AND APPARATUS - The embodiments provide a multi-stage phase estimation method and apparatus. The apparatus i a multi-stage phase estimation configuration. Each stage of the phase estimation configuration includes metric computation modules. Each of the metric computation modules computing a distance metric and search phase angles according to an input signal and an initial search phase angle or a search phase angle of the former stage phase estimation configuration. The number of the metric computation modules is equal to that of the search phase angles of this stage. A selection module selects the search phase angle corresponding to the minimal distance metric as the phase estimation result output of this stage according to the computation results of all metric computation modules. The average time window length of the former stage phase estimation configuration is larger than that of the subsequent stage phase estimation configuration. | 10-25-2012 |

20120275797 | POLARIZATION SCATTERING COMPENSATION DEVICE AND POLARIZATION SCATTERING COMPENSATION METHOD - Polarization scattering compensation device and method are disclosed. In the device, a time sequence alignment unit aligns time sequences of signals in the first and second polarization state transmitted simultaneously; a polarization scattering estimation unit estimates a scattering coefficient of a scattering by the signal in the first polarization state on the signal in the second polarization state, and a scattering coefficient of a scattering by the signal in the second polarization state on the signal in the first polarization state; and a polarization scattering removal unit removes the scattering by the signal in the first polarization state on the signal in the second polarization state, and the scattering by the signal in the second polarization state on the signal in the first polarization state, in accordance with the scattering coefficients. | 11-01-2012 |

20120290244 | METHOD AND APPARATUS FOR COMPENSATING NONLINEAR DAMAGE - A method and apparatus for compensating nonlinear damage are disclosed. The method for compensating nonlinear damage, including: determining an additive parameter indicating an amount of nonlinear damage based on a plurality of sampled signal sets among which a sampling time of an input signal varies according to different time; and subtracting the additive parameter from the input signal. | 11-15-2012 |

20130077979 | NONLINEAR COMPENSATING APPARATUS AND METHOD AND TRANSMITTER - The present invention provides a nonlinear compensating apparatus and method and a transmitter. The nonlinear compensating apparatus includes: an information sequence acquiring unit, configured to acquire a symbol information sequence of the pulse signal; a perturbation quantity acquiring unit, configured to calculate the weighted sum of interaction items of pulses on one or more moments relative to the current moment, to obtain the perturbation quantity produced on a transmission link with a certain length, and rotate the obtained perturbation quantity by a predetermined phase; and an information compensating unit, configured to calculate the difference between the symbol information sequence and the perturbation quantity to obtain a compensated symbol information sequence. With the embodiments of the present invention, the performance of the system, especially the performance of NRZ (Not Return to Zero) code, may be further improved. | 03-28-2013 |

20130094852 | FREQUENCY OFFSET MONITORING DEVICE AND OPTICAL COHERENT RECEIVER - The present invention provides a frequency offset monitoring device and an optical coherent receiver. A low speed frequency offset monitoring device comprises a signal speed lowering section, for lowering the speed of an inputted signal and outputting the speed lowered signal, and a frequency offset monitor, for monitoring frequency offset of the speed lowered signal outputted by the signal speed lowering section. | 04-18-2013 |

20130108260 | METHOD AND APPARATUS FOR ADAPTIVE NONLINEAR EQUALIZATION IN A POLARIZATION MULTIPLEXING OPTICAL COMMUNICATION SYSTEM | 05-02-2013 |

20130188948 | NONLINEAR ESTIMATING APPARATUS AND METHOD AND RECEIVER - The present invention provides a nonlinear estimating apparatus and method, and a receiver. The nonlinear estimating apparatus includes: an information sequence acquiring unit, configured to acquire a symbol information sequence of the pulse signal inputted by a transmitting side; a perturbation quantity generating unit, configured to calculate the weighted sum of the interaction items of the pulses on one or more moments relative to the current moment, so as to obtain an additive perturbation quantity and a multiplicative perturbation quantity produced on a transmission link with a certain length; and a signal estimating unit, configured to estimating the signal received at a receiving side according to the symbol information sequence, the additive perturbation quantity and the multiplicative perturbation quantity. With the embodiments of the present invention, the accuracy of estimation of nonlinear signals may be further improved. | 07-25-2013 |

20130216238 | NONLINEAR COMPENSATING APPARATUS AND METHOD AND TRANSMITTER - The present invention provides a nonlinear compensating apparatus and method and a transmitter. The nonlinear compensating apparatus includes: an information sequence acquiring unit, configured to acquire a symbol information sequence of the pulse signal; a perturbation quantity acquiring unit, configured to calculate, by pre-obtained weighting coefficients to which each item corresponds, the weighted sum of interaction items of pulses on one or more moments relative to the current moment; a perturbation quantity processing unit, configured to combine the items of the perturbation quantity based on the weighting coefficients; and an information compensating unit, configured to calculate a difference between the symbol information sequence and the processed perturbation quantity to obtain a compensated symbol information sequence. With the embodiments of the present invention, the complexity of calculation may be further lowered, and requirements on hardware may also be lowered. | 08-22-2013 |

20130230313 | METHOD AND APPARATUS FOR COMPENSATING NONLINEAR DAMAGE - The embodiments relate to a method and an apparatus for compensating nonlinear damage. The method and apparatus being used in a dual-polarization communication system, the method comprising: calculating, according to input time-domain signals, a plurality of multiplicative parameters indicative of nonlinear damages to the input signals; constructing a plurality of multiplicators by using the plurality of multiplicative parameters; and compensating the input time-domain signals by using the plurality of multiplicators. | 09-05-2013 |

20130243433 | INVERSE CHANNEL APPARATUS AND TRANSMITTER, RECEIVER AND SYSTEM CONTAINING THE APPARATUS - The embodiments of the present invention provide an inverse channel apparatus and transmitter, receiver and system containing the apparatus; wherein the inverse channel apparatus comprises: an inverse nonlinear calculating unit configured to perform nonlinear additive calculation and nonlinear multiplicative calculation on input signals, so as to obtain signals containing nonlinear damage of the input signals on at least one polarization state; and an inverse linear calculating unit configured to calculate signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the signals containing nonlinear damage of the input signals on at least one polarization state and a linear function of a channel. The advantages of the embodiments of the present invention exist in that a transmitted signal is recovered by being passed through an inverse channel after or before being transmitted in a practical channel, thereby effectively compensating for intra-channel nonlinear damage of an optical fiber communication system. | 09-19-2013 |

20130266311 | METHOD AND APPARATUS FOR ESTIMATING CROSS-PHASE MODULATION IMPAIRMENTS - A system for estimating cross-phase modulation (XPM) impairments, wherein the method comprises: determining, according to a pump Jones matrix of a pump channel and a probe Jones matrix of a probe channel of each of fiber spans except for the first fiber span in a fiber transmission system, a polarization mode dispersion (PMD)-induced relative polarization status rotation matrix between channels of the each of fiber spans; and determining, according to the rotation matrix of the each of fiber spans, dispersion of a pump signal of the each of fiber spans, differential delay of the pump signal relative to a probe signal of the each of fiber spans and a gain of the each of fiber spans, polarization crosstalk and phase noise of the XPM impairments in the fiber transmission system. This allows the XPM impairments in the effect of the polarization mode dispersion to be quickly and accurately estimated, | 10-10-2013 |

20130272719 | Method and Apparatus for Compensating Nonlinear Distortions in Intensity Modulation-Direct Detection System - The embodiments of the present invention provide a method and an apparatus for compensating nonlinear distortions in an intensity modulation-direct detection (IM-DD) system; wherein the method comprises: calculating, according to nonlinear coefficients and differences between values of an input signal at different time, nonlinear distortions of the input signal, so as to eliminate the nonlinearity distortions. By applying the method and the apparatus provided by the embodiments of the present invention, nonlinear cost of the IM-DD system can be effectively reduced, thereby improving the system capacity. | 10-17-2013 |

20140010533 | AUTOMATIC BIAS CONTROL METHOD AND APPARATUS FOR OPTICAL TRANSMITTER - The embodiments provide an automatic bias control method and apparatus for an optical transmitter. The apparatus includes: a detecting unit configured to monitor output optical power of an I/Q modulator of the optical transmitter; a calculating unit configured to calculate bias voltage indicating values of the I modulator, Q modulator and phase modulator of the I/Q modulator according to the output optical power and known modulation data; and an adjusting unit configured to adjust respectively Direct-Current (DC) bias voltages of the I modulator, Q modulator and phase modulator according to the bias voltage indicating values of the I modulator, Q modulator and phase modulator. With the embodiments, known modulation data are used to realize automatic bias control by monitoring the evenness of distribution of the power of output optical signals of the transmitter in the four quadrants of an I/Q plane. | 01-09-2014 |

20140037032 | Receiver and Receiving Method - Embodiments of the present invention provide a receiver and a receiving method. The receiver comprises: a branch forming unit a plurality of signal branches; each of the signal branches comprising a joint processing unit; and the joint processing unit being used to eliminate an inter-carrier interference of the subcarrier signal in a present signal branch and the subcarrier signals in other signal branches adjacent to the present signal branch. With the embodiments of the present invention, the inter-carrier interference may be eliminated and the performance of the system may be improved; and the sampling rate of the analog digital converter may also be lowered. | 02-06-2014 |

20140079407 | UPDATING APPARATUS AND METHOD FOR EQUALIZER COEFFICIENT, RECEIVER AND OTPICAL COMMUNICATION SYSTEM - The present invention provides an updating apparatus and method for an equalizer coefficient, receiver and optical communication system. The updating method comprises: receiving an optical signal transmitted by a transmitter in an optical communication system, the optical signal comprising transmission data and a constant modulus signal for updating a coefficient of an equalization filter; performing coherent detection and analog-to-digital conversion on the optical signal, so as to obtain a digital electric signal; and updating the coefficient of the equalization filter at a symbol corresponding to the constant modulus signal in the digital electric signal. With the embodiments of the present invention, not only the coefficients of the equalizer may be optimized, but also being adapted to signals in various modulation formats, and the complexity of the channel equalization may be lowered as well. | 03-20-2014 |

20140079408 | COEFFICIENT DETERMINING APPARATUS, EQUALIZER, RECEIVER AND TRANSMITTER - Embodiments of the present invention provide a coefficient determining apparatus, equalizer, receiver and transmitter. The coefficient determining apparatus comprises: a synchronizer configured to find a position of a training sequence from signals containing the training sequence received by a transmitter; and a first processor configured to set an initial tap coefficient of an equalizer according to the received signals and the training sequence; wherein in each polarization state, the training sequence comprises n pairs of training symbols, in the n pairs of training symbols, the training symbols of the same pair being identical, the training symbols of the different pair being different, a cyclic prefix and a cyclic postfix being respectively inserted before and after each pair of training symbols, and n being an integer greater than 1. By using the training sequence contained in the transmitted signals to determine an initial tap coefficient of the equalizer relatively close to the optimal value, channel damages may be approximately compensated, and the receiver is facilitated in further processing the signals. | 03-20-2014 |

20140095129 | NONLINEAR TERM SELECTION APPARATUS AND METHOD, IDENTIFICATION SYSTEM AND COMPENSATION SYSTEM - The embodiments of the present invention provide a nonlinear term selection apparatus and method, an identification system and a compensation system. The selection apparatus comprises: a linear coefficient calculator configured to measure linear properties of a nonlinear system by using measurement data, so as to obtain a plurality of linear coefficients; and a nonlinear term selector configured to select nonlinear model expanded terms of the nonlinear system by using the plurality of linear coefficients, so as to obtain nonlinear terms of the nonlinear system. With the embodiments of the present invention, the nonlinear model may be simplified, and the complexity of the nonlinear model may be lowered. | 04-03-2014 |

20140105616 | PHASE DETECTION METHOD AND APPARATUS FOR CLOCK RECOVERY - Embodiments of the present invention provide a phase detection method and apparatus. The apparatus comprises a phase detector, the phase detector comprising a calculation unit configured to calculate a phase difference according to a product of receiving power at different moments, so as to perform clock recovery by using the phase difference; wherein the receiving power is that obtained in sampling input signals at a predefined sampling rate, the predefined sampling rate being 2 times of a symbol rate. With the method and apparatus of the embodiments of the present invention, the problem that in case of a relatively large frequency difference or line width, or the transmitted signals are Nyquist signals of spectral widths close to the symbol rate, a conventional phase detection method will be invalid, is solved by calculating a phase difference only according to a product of receiving power at different moments. | 04-17-2014 |