Abstract: 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.

Abstract: Embodiments of the present disclosure provide a monitoring apparatus for an optical signal to noise ratio, a signal transmission apparatus and a receiver. White noise power of received signals is calculated according to noise power and power of pilot signals of the received signals in different polarization states, and influence of a nonlinear noise is excluded, thereby accurately estimating an optical signal to noise ratio, for example, with a calculation process being simple and an application range being relatively wide.

Abstract: An estimating apparatus for bias drift of a transmitting end modulator, a compensating apparatus, a receiver and a method are disclosed. Estimation and compensation of the bias drift are performed directly at the receiving end according to phase recovered received signals, with no need of providing an extra bias control circuit at the transmitting end. Estimating and compensating for the bias drift includes recovering received signals by removing a frequency difference and a phase difference between a transmitting end laser and a receiving end laser producing phase recovered received signals, estimating the bias drift of the transmitting end modulator according to the phase recovered received signals and compensating the bias drift of the transmitting end modulator in a receiver.

Abstract: Embodiments of the present disclosure provide an apparatus and method for detecting channel spacing and a system. The apparatus for detecting channel spacing includes a first estimating unit configured to estimate a frequency offset of a center channel according to a received signal, a second estimating unit configured to estimate a frequency offset of a neighboring channel according to the received signal, and a determining unit configured to determine channel spacing according to the frequency offset of the center channel estimated by the first estimating unit and the frequency offset of the neighboring channel estimated by the second estimating unit. With the embodiments of the present disclosure, estimation accuracy of channel spacing may be ensured, and influence of non-ideal factors on estimation value may be reduced.

Abstract: Embodiments of the present disclosure provide a method and apparatus for determining a nonlinear characteristic and a system. The method for determining a nonlinear characteristic includes: determining a correction factor of a nonlinear item of a nonlinear model of a system to be measured according to an input and/or a parameter of the system to be measured; correcting the nonlinear item of a nonlinear model of the system to be measured by using the correction factor; and obtaining a nonlinear characteristic of the system to be measured according to the corrected nonlinear model. The nonlinear characteristic allows the input and/or the parameter of the system to be corrected to produce a corrected output. With the embodiments of the present disclosure, the nonlinear characteristic of the system to be measured under different inputs and/or parameters may be estimated, and accuracy of the estimation and applicability are improved.

Abstract: A transmitter generates a frequency-modulated CW light so as to transmit it to a path. A receiver receives the CW light that has passed through passband filters included in the path. The receiver includes a processor. The processor measures an optical power of the received CW light every time a center frequency of the CW light is changed and transmitted by the transmitter. The processor calculates transmission characteristics of the CW light that has passed through the passband filters, on the basis of an average value of the optical power that corresponds to a center frequency of the CW light and on the basis of an amplitude component that indicates an amount of change in the optical power, the average value and the amplitude component being obtained as a result of the measurement.

Abstract: A bias monitoring method and apparatus and a transmitter, the bias monitoring apparatus being used for monitoring deviation of a direct current bias point of an optoelectronic modulator and including: a first signal processing unit configured to perform first signal processing on an electric driving signal inputted into the optoelectronic modulator, so as to output a reference signal; a second signal processing unit configured to perform second signal processing on an electric output signal obtained based on an optical signal outputted by the optoelectronic modulator, so as to output a monitoring signal; and a monitoring signal calculating unit configured to calculate correlation between the reference signal and the monitoring signal, and output a calculation result of the correlation as a bias monitoring signal. The sensitivity of the bias monitoring apparatus may be improved, and complexity of hardware may be lowered.

Abstract: Embodiments of the present disclosure provide a signal processing apparatus, a signal transmitting apparatus and a receiver, which are adapted for a frequency division multiplexing system having a high-order modulation format. A receiver having a high-magnification sampling rate by inserting a pilot signal between neighboring subcarriers at a transmitter side, calculating a laser phase noise according to a phase of the pilot signal at a receiver side, and performing down-sampling and equalization processing after performing carrier phase recovery according to the laser phase noise, so that a laser phase noise having a wide frequency may be accurately compensated, thereby having a relatively powerful carrier phase recovery ability.

Abstract: A method, apparatus and system estimating channel power, and monitoring a frequency spectrum characteristic. A method for estimating channel power includes extracting frequency spectrum information from a received signal, so as to obtain a frequency spectrum of the received signal, estimating power of a central channel in the frequency spectra according to a power value of a flat area of the central channel, and estimating power of a neighboring channel in the frequency spectra according to a power value of a flat area of the neighboring channel. With the embodiments of the present disclosure, the power of the central channel and the power of the neighboring channel may be estimated by using only frequency spectrum information obtained by a single optical receiver, so as to quantitatively evaluate influence of a power imbalance effect, thereby ensuring precision of the power estimation, and reducing effects of nonideal factors on the estimated values.

Abstract: Embodiments of the present disclosure provide an estimation apparatus and method for a nonlinear characteristic, which may simply and quickly estimate the nonlinear characteristic of a system to be measured by calculating parameters of the nonlinear model of the system to be measured according to the fundamental power and harmonic power of output signals of the system to be measured on at least two frequency spots obtained through measurement, with the accuracy of the result of estimation being relatively high.

Abstract: Embodiments of the present disclosure provide a monitoring apparatus for an optical signal to noise ratio, a signal transmission apparatus and a receiver. The monitoring apparatus includes a selecting unit configured to select a time domain, and/or frequency domain range for calculating noise power of received signals according to a location of a pilot signal in the received signals in a time domain and/or frequency domain, and a calculating unit configured to calculate the noise power of the received signals according to the received signals in the selected range of the time domain and/or frequency domain, and calculate an optical signal to noise ratio of the received signals according to the noise power. The optical signal to noise ratio may be accurately estimated, with a process of calculation being simple and a scope of application being relatively wide.

Abstract: 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.

Abstract: Embodiments of the present disclosure provide an estimation apparatus and compensation apparatus for clipping distortion of multicarrier signals and a receiver. The estimation apparatus includes: a first calculating unit configured to multiply an error signal of each subcarrier in all or part of subcarriers in received multicarrier signals by a conjugation of an error signal of a subcarrier neighboring or spaced apart from each subcarrier; a second calculating unit configured to calculate an average value of all results of multiplication; a third calculating unit configured to calculate parameters of the clipping distortion of the multicarrier signals according to the average value; and an estimating unit configured to estimate the clipping distortion of the multicarrier signals according to the calculated parameters of the clipping distortion.

Abstract: An information transmission apparatus, an information detection apparatus and a transmitter is provided where serial numbers of information transport blocks are determined according to information indicating branch selection, so as to transmit information on the branch selection by using the serial numbers of information transport blocks. Hence, no additional transmission path needs to be provided, and the information on the branch selection may be simply and conveniently transmitted and a probability of wrongly determining the information indicating branch selection may be reduced, thereby efficiently improving performance of the system.

Abstract: A monitoring apparatus and method for an optical signal-to-noise ratio and a receiver, where the apparatus includes: a processing unit configured to perform nonlinear processing on a pilot signal in received signals, or on a pilot signal in received signals and data signals in a predefined range neighboring the pilot signal; and a calculating unit configured to calculate an optical signal-to-noise ratio of the received signals according to a result of the nonlinear processing. Complexity of calculation may be lowered and accuracy of calculation of an optical signal-to-noise ratio may be improved, thereby efficiently improving the performance of the system.

Abstract: An apparatus for estimating channel spacing, an apparatus for monitoring wavelength and a receiver where the apparatus for estimating channel spacing includes: a measuring unit configured to measure a spectrum gap width according to spectrum information of a received signal; and a determining unit configured to determine channel spacing by using the spectrum gap width according to a predefined corresponding relationship between channel spacing and spectrum gap width. And in this application, the measuring unit may determine reference power according to a predefined reference power level, and take a frequency difference between two frequency points in a left or right gap of a central channel in the spectrum information of the received signal corresponding to the reference power as the spectrum gap width. With this application, accuracy of wavelength monitoring may be improved.

Abstract: A method and apparatus for correcting inter-channel power imbalance and a receiver, applicable to a receiver in a multicarrier optical communication system, where the method includes: receiving by the receiver reference information transmitted by a neighboring receiver; and performing power imbalance error correction by the receiver according to the reference information. With this application, based on performing signal processing in the receiver, estimation errors produced due to power imbalance in the central channel and the neighboring channel may be reduced.

Abstract: A nonlinear compensation method and apparatus and a system in a multicarrier optical communication system where the method includes: determining a coefficient of a linear filter in nonlinear compensation according to an end-to-end channel linear response of the system; determining taps of a nonlinear compensation filter needing to be opened and coefficients of the taps according to a hardware compensation ability of the system and the coefficient of the linear filter; and compensating for a nonlinear damage of the system by using the selected coefficients of the nonlinear compensation filter. With the method, apparatus or the system provided by this application, very good compensation performance may be achieved in a range of power consumption of the multicarrier optical communication system by only opening and using few taps of the compensation filter.

Abstract: 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.

Abstract: 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.