Fujitsu Corporation

Socionext Inc.

Weizhen Yan

Zhenning Tao

Lei Li

Bo Liu

Hao Chen

Takeshi Hoshida

Andrzej Radecki

Toshiki Tanaka

Shoichiro Oda

Yinwen Cao

A bit allocation method, apparatus for a multicarrier modulation signal and a system where the method includes: lowering the number of bits of a subcarrier of minimum average power in subcarriers of the multicarrier modulation signal allocated with a maximum number of bits according to a predetermined total number of bits to be adjusted including setting a total number of bits to be adjusted; determining a target number of bits according to the total number of bits; allocating a bit number for each subcarrier of the multicarrier modulation signal by using a predetermined bit allocation method according to the target; and lowering the number of bits of a subcarrier of minimum average power in the subcarriers allocated with a maximum number of bits, until a lowered total number of bits is equal to the total number of bits to be adjusted.

Bit allocation method, apparatus for multicarrier modulation signal, and system

A signal transmission apparatus includes: a first receiving unit to receive a probe signal transmitted by transmitting end; wherein, the signal is generated based on a recommended signal configuration from previous signal to noise ratio (SNR) probings; a first processing unit to probe a channel SNR according to the signal; a first determining unit to determine transmission signal configuration and signal transmission performance of a final channel SNR obtained by multiple SNR probings; and a first transmitting unit to transmit the configuration and the performance to the transmitting end, where the transmitting end transmits an actual transmission signal according to the configuration and the performance.

Signal transmission apparatus and multicarrier communication system

A channel equalization and tracking apparatus and method and a receiver. The apparatus includes: a Fourier transforming unit configured to transform a received time-domain signal into a frequency-domain signal; a compensating and equalizing unit configured to perform phase compensation and frequency-domain equalization on the signal outputted by the Fourier transforming unit by using one time of multiplication according to time delay information and an equalizer coefficient; a deciding unit configured to decide the equalized signal; and a channel tracking unit configured to track a channel according to the signal outputted by the Fourier transforming unit and an error signal obtained by the deciding unit. With embodiments of the present disclosure, not only complexity and hardware demands of the whole system are lowered, but also performance of the system is not affected.

Channel equalization and tracking apparatus and method and receiver

An adaptive equalizer, an adaptive equalization method and receiver are disclosed where the adaptive equalizer is used for performing adaptive equalization processing on a frequency-domain signal, a channel used by the frequency-domain signal containing multiple subcarriers, the adaptive equalizer comprises: an equalizer coefficient generating unit configured to, for each subcarrier, generate an equalizer coefficient to which the subcarrier corresponds according to channel information and a step length of the subcarrier; where different subcarriers correspond to different step lengths and an equalization processing unit configured to, for each subcarrier, perform equalization processing on a signal in the subcarrier by using the equalizer coefficient.

Adaptive equalizer, adaptive equalization method and receiver

A nonlinear compensating apparatus and method, a transmitter and a communication system are provided. The apparatus includes a preprocessor configured to preprocess a transmitted signal according to a pre-obtained preprocessing coefficient and a predistorter configured to perform predistortion for the preprocessed signal, and a result of comparison of a characteristic parameter of the signal that has been preprocessed and then predistorted with that of the transmitted signal satisfies a predetermined condition. By preprocessing the transmitted signal at the transmitter end, the embodiments of the present disclosure may perform efficient nonlinear compensation only needing to measure at the transmitter end and without needing to perform many times of measurement at the receiver end, and may lower complexity of circuits of the communication system and complexity of calculation.

Nonlinear compensating apparatus and method, transmitter and communication 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.

Nonlinear term selection apparatus and method, identification system and compensation system

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.

Method and apparatus for estimating cross-phase modulation impairments

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.

Method and apparatus for compensating nonlinear distortions in intensity modulation-direct detection system

Embodiments of the present invention provide a timing synchronization apparatus and method for multi-carrier modulation signals. Wherein the apparatus includes: a predicting unit configured to denoise delay of symbols received before a currently received symbol, and to predict delay of the currently received symbol or of a symbol received after the currently received symbol according to the denoised symbol delay and a sampling clock frequency offset; and a timing synchronization unit configured to perform timing synchronization according to a predicted value of the delay of the currently received symbol or of the symbol received after the currently received symbol. With the apparatus and method, a signal to noise ratio of multi-carrier modulation signals may be effectively improved, and an effect of a timing error on a communication system may be lowered, thereby improving performance of the communication system.

Timing synchronization apparatus and method for multi-carrier modulation signals

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.

Method and apparatus for compensating nonlinear damage

A method and apparatus for adaptive nonlinear equalization, comprising: a horizontal polarization component compensation unit configured to calculate a linear damage value of an input signal, a nonlinear damage value of a horizontal component of the input signal, and a crosstalk value caused by a vertical component to the horizontal component, and compensate the horizontal component according to the linear damage value, the nonlinear damage value and the crosstalk value; and, a vertical polarization component compensation unit configured to calculate a linear damage value of the input signal, a nonlinear damage value of a vertical component of the input signal, and a crosstalk value caused by a horizontal component to the vertical component, and compensate the vertical component according to the linear damage value, the nonlinear damage value and the crosstalk value. With the present invention, Intra-channel nonlinear damage of a polarization multiplexing optical communication system is effectively compensated.

Method and apparatus for adaptive nonlinear equalization in a polarization multiplexing optical communication system

Embodiments of the present disclosure provide a sequence synchronization apparatus and method and a receiver. The sequence synchronization apparatus includes: a signal receiving unit configured to receive a clock synchronized signal including a training symbol, the training symbol being in-phase modulated or being modulated with a fixed phase difference based on all or part of subcarriers; and a symbol detecting unit configured to detect the training symbol, so as to achieve sequence synchronization of the signal. With the embodiments of the present disclosure, not only sequence synchronization may be achieved by using minimum complexity as possible, but also the sequence synchronization apparatus is made simple, fast and accurate.

Sequence synchronization apparatus and method and receiver

The embodiments 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 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.

Inverse channel apparatus and transmitter, receiver and system containing the apparatus

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.

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.

Growing community of inventors

Beijing, China

Weizhen Yan