Abstract: A method and an apparatus for evaluating transmission impairments of a multiplexing converter. According to the method, impairments of a multiplexing converter are equivalent to the equivalent multiplicative noise and the equivalent additive noise, so as to allow evaluation of transmission impairments of the multiplexing converter, thereby to allow evaluation of the performance of a communication system. The multiplexing converter is a multiplexing analog-to-digital converter, or a multiplexing digital-to-analog converter. According to the present application, impairments of a multiplexing converter can be evaluated accurately, the performance evaluation of a communication system using the multiplexing converter is given, without being affected by an amplitude, a modulation format and a transmission rate of an input signal.

Abstract: An optical signal transmission device and method based on digital predistortion in a symbol domain is provided. The optical signal transmission device includes: a memory; and a processor coupled to the memory to control execution of a process to: perform digital predistortion processing on a symbol sequence of a signal to be transmitted to obtain a digital predistortion processed signal; perform short-pulse shaping processing on the digital predistortion processed signal to obtain a short-pulse shaping processed signal, wherein a memory length introduced by the short-pulse shaping processing is less than or equal to a memory length of the optical transmitter; and generate and transmit an optical signal based on the short-pulse shaping processed signal.

Abstract: A distorter coefficient updating apparatus, a distorter coefficient updating method, and a digital predistortion apparatus. The distorter coefficient updating apparatus is configured at an optical receiver side, and comprises a processor configured to: perform re-distortion processing on a signal after decision according to a first distorter coefficient to generate a first reference signal; and calculate a second distorter coefficient according to the first reference signal and a signal before decision, or according to the first reference signal, the signal after decision, and the signal before decision The second distorter coefficient is fed back to the processor as the first distorter coefficient of the processor in a next update, and the second distorter coefficient is fed back to a predistorter on an optical transmitter side as a predistortion coefficient for the predistorter to perform a predistortion processing on a signal input to the predistorter.

Abstract: The present disclosure provides an apparatus and method for measuring a nonlinear signal-to-noise ratio, and a test instrument. The method for measuring a nonlinear signal-to-noise ratio may include performing notch operation on at least one frequency point in a spectrum of an input signal in a symbol domain or a bit domain; performing spectrum measurement on an output signal after passing through a nonlinear system; and estimating a nonlinear signal-to-noise ratio of at least one frequency point of the nonlinear system according to a spectrum of the output signal. According to the embodiments of the present disclosure, when the notch operation is performed, internal structures of symbols or bits of the input signal may be retained, and an accuracy of the measurement of the nonlinear signal-to-noise ratio may be improved.

Abstract: A method, an apparatus and a communication system of evaluating a nonlinear compensation performance. The method for evaluating a nonlinear compensation performance comprises: evaluating a nonlinear compensation performance by using a probability-maintained notch signal as a test signal; the probability-maintained notch signal having a probability density function (PDF) that is maintained unchanged after notching as compared with before notching.

Abstract: An apparatus and method to measure nonlinear system noises may include a processor to generate a bilateral notch signal, a unilateral notch signal and a multi-tone signal; to measure power of an additive Gaussian white noise of a nonlinear system by using the multi-tone signal; to measure a first power-to-noise ratio of the nonlinear system by using the bilateral notch signal; to measure a second power-to-noise ratio of the nonlinear system by using the unilateral notch signal. The processor is to calculate a nonlinear power-to-noise ratio of the nonlinear system and a power-to-noise ratio introduced by IQ imbalance according to the power of the additive Gaussian white noise, the first power-to-noise ratio and the second power-to-noise ratio.

Abstract: A signal generation apparatus and method. The apparatus includes: a memory, and a processor coupled to the memory to control execution of a process to: perform dispersion processing on a two-dimensional reference signal to obtain a two-dimensional dispersion signal; perform at least one time of equiprobability processing, perturbation processing and isospectral processing on a two-dimensional input signal according to the two-dimensional dispersion signal; and output a two-dimensional isospectral equiprobability signal generated, when an equiprobability processed signal or an isospectral processed signal satisfies a predetermined condition, wherein in the equiprobability processing.

Abstract: Embodiments of this disclosure provide a measurement apparatus and method for nonlinear damages in an optical link. The apparatus may include a processor to control execution of a process to generate multiple band-notch signals with different band-notch widths corresponding to a frequency point to be measured; and calculate respective multiple nonlinear noise-to-power ratios at the frequency point to be measured according to multiple band-notch signals obtained after the multiple band-notch signals with different band-notch widths pass through the optical link. A real nonlinear noise-to-power ratio may be extrapolated at the frequency point to be measured according to the multiple nonlinear noise-to-power ratios corresponding to the multiple band-notch signals with different band-notch widths.

Abstract: A polarization change tracking apparatus, a processing apparatus for a received signal and methods thereof. The polarization change tracking method includes: estimating a polarization change speed in a link according to a received signal; setting a response coefficient of polarization tracking according to a relationship between an estimated polarization change speed and a predetermined value, to make a response of polarization tracking and a response of adaptive equalization be consecutive; and performing compensation for polarization change on the received signal according to a set response coefficient of polarization tracking.

Abstract: A method, an apparatus and a system to measure nonlinear related parameters of a nonlinear device. The apparatus comprises a memory and a processor coupled to the memory to control execution of a process to: generate a first signal according to a signal to be measured, the first signal and the signal to be measured having a signal probability distribution that is same, and the first signal having at least one notch frequency; and calculate, according to an output signal of the nonlinear device when the first signal is input into the nonlinear device, nonlinear related parameters of the nonlinear device when the signal to be measured is transmitted.

Abstract: A method, an apparatus and a system to measure nonlinear correlation parameters of a nonlinear device, a processor to, perform band-stop filtering on a signal to be measured to generate a notch signal, and calculate a first nonlinear correlation parameter of the nonlinear device when the signal to be measured is transmitted according to a first output signal of the nonlinear device after the notch signal is input into the nonlinear device; calculate gain compression correction coefficients according to a second output signal of the nonlinear device after the first input signal is input into the nonlinear. The first input signal and the signal to be measured may have identical power and different signal probability distribution. The processor is to correct the first nonlinear correlation parameter according to the gain compression correction coefficients to obtain a second nonlinear correlation parameter of the nonlinear device when the signal to be measured is transmitted.

Abstract: A polarization recovery apparatus, a method thereof and an optical receiver. The method includes: performing adaptive equalization processing and polarization recovery on a received signal, wherein a polarization state of the received signal, after the adaptive equalization processing and polarization recovery being performed, is aligned with a principal axis of polarization of an optical receiver.

Abstract: A performance estimation apparatus and method for a nonlinear communication system and an electronic device. The nonlinear communication system is equated with by an equivalent model including an equivalent linear model and an equivalent additive noise model, and the equivalent additive noise outputted by the equivalent additive noise model is mathematically uncorrelated to the signal inputted into the equivalent model. Performances of the nonlinear communication system of different modulation formats at different baud rates may be accurately estimated.

Abstract: The present disclosure provides a method and apparatus for generating equivalent nonlinear noise. The method includes randomly generating white noise obeying zero-mean Chi-square distribution; and filtering the input white noise by using an equivalent nonlinear noise spectrum as an equivalent nonlinear filter to obtain the equivalent nonlinear noise. According to the embodiments of the present application, equivalent nonlinear noise may be generated based on zero-mean Chi-square distribution random variables combined with equivalent nonlinear noise spectrum filtering, and more accurate equivalent nonlinear noise than the related art may be generated, thus accurately evaluating an influence of nonlinearity of devices on Bit Error Rate (BER).

Abstract: The present disclosure provides an apparatus and method for measuring a nonlinear signal-to-noise ratio, and a test instrument. The method for measuring a nonlinear signal-to-noise ratio may include performing notch operation on at least one frequency point in a spectrum of an input signal in a symbol domain or a bit domain; performing spectrum measurement on an output signal after passing through a nonlinear system; and estimating a nonlinear signal-to-noise ratio of at least one frequency point of the nonlinear system according to a spectrum of the output signal. According to the embodiments of the present disclosure, when the notch operation is performed, internal structures of symbols or bits of the input signal may be retained, and an accuracy of the measurement of the nonlinear signal-to-noise ratio may be improved.

Abstract: A method and apparatus for generating a signal. The method includes: by taking a reference signal as a standard, cyclically performing isoprobabilistic processing and isospectral processing, or cyclically perform isoprobabilistic processing, perturbation processing and isospectral processing, on an input signal, until an obtained signal satisfies both a requirement on a target probability distribution and a requirement on a target spectrum, where a probability distribution of the reference signal satisfying the requirement on a target probability distribution, the isoprobabilistic processing referring to processing that makes the probability distribution of an output signal identical to the probability distribution of the reference signal. Therefore, a signal that satisfies both the requirement on the specific probability distribution and the requirement on the spectrum can be generated, and the degree of compliance is higher.

Abstract: An apparatus at least includes a processor to, after a first signal passes through a narrowband photodetector, perform frequency mix of the first signal with a first reference signal and a second reference signal respectively and perform noise reduction, to obtain a first detection signal and a second detection signal. The first signal is obtained after a measurement signal passes through a filtering module of an optical transmitting end, the measurement signal being transmitted in a path of multiple branches, signals not transmitted in other paths of the multiple branches, a frame structure of the measurement signal including at least one two-tone signal, two tones in the two-tone signal having a fixed tone interval.

Abstract: A distorter coefficient updating apparatus, a distorter coefficient updating method, and a digital predistortion apparatus. The distorter coefficient updating apparatus is configured at an optical receiver side, and comprises a processor configured to: perform re-distortion processing on a signal after decision according to a first distorter coefficient to generate a first reference signal; and calculate a second distorter coefficient according to the first reference signal and a signal before decision, or according to the first reference signal, the signal after decision, and the signal before decision The second distorter coefficient is fed back to the processor as the first distorter coefficient of the processor in a next update, and the second distorter coefficient is fed back to a predistorter on an optical transmitter side as a predistortion coefficient for the predistorter to perform a predistortion processing on a signal input to the predistorter.

Abstract: A method for updating a non-linear look-up table, an apparatus for updating a non-linear look-up table, and an optical receiver. The method for updating a non-linear look-up table includes: performing suppression processing on residual linear ISI contained in an input look-up table in an iterative update process of a look-up table to obtain a processed look-up table. The method eliminates adverse effects of a residual linear ISI in real time during an iterative update process of a LUT, so that a generated LUT coefficient does not continue to diverge along an iteration process, which ensures stable operation of pre-compensating on nonlinearity of an optical transmitter device.

Abstract: This disclosure provides a signal generation device and an equalization processing device. The signal generation device generates a pilot sequence and payload, the pilot sequence and the payload having identical or similar amplitude probability characteristics. Hence, nonlinear interference may be resisted, and performance of the communication system may be improved.