Fujitsu Corporation

Yangyang Fan

Zhenning Tao

Liang Dou

Jingnan Li

Ke Zhang

Xiaofei Su

Junpeng Liang

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.

Measurement apparatus and method for nonlinear damages in optical link

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.

Polarization change tracking apparatus, processing apparatus for received signal and methods thereof

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.

Polarization recovery apparatus and method thereof and optical receiver

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. The processor is to calculate group delays at multiple frequency bins according to the first detection signal and the second detection signal; and determine a phase response of the filtering module of the optical transmitting end in the path according to the group delays at multiple frequency bins.

Phase response measurement method and apparatus

An apparatus and method to monitor a polarization change by inserting pilot signals in a transmission signal and converting the pilot signals in the receiving signal from a Jones space into a Stokes space. A velocity of a polarization change of the optical link is estimated by using the Stokes vectors of the pilot signals, thereby directly and accurately estimating the polarization change of the optical link. Moreover, estimation of the velocity of the polarization may be applicable where rotation of state of polarization and polarization-dependent loss coexist in an optical link.

Apparatus and method for monitoring polarization change

A state of polarization tracking recovery method and apparatus. The apparatus at least includes a processor configured to fit Stokes vectors to which predetermined symbols correspond of two states of polarization in a received dual-polarization multiplexing optical signal on a Poincare sphere to obtain a fitted plane. The processor calculates a compensation matrix for polarization-dependent loss (PDL) in a Jones space by moving a center of the fitted plane to the origin of the Poincare sphere, and calculates a demultiplexing matrix used for polarization demultiplexing in a Jones space by rotating the fitted plane with the center being moved to the origin until a normal vector of the fitted plane is parallel with a first axis of the Stokes space and rotating the fitted plane with the center being moved to the origin to a plane constituted by a second axis and a third axis of the Stokes space.

State of polarization tracking recovery method and apparatus

Embodiments of this disclosure provide an apparatus and method for determining coefficients of a fixed equalizer, the fixed equalizer being applicable to performing fixed equalization on an optical communications system, the apparatus including: a first acquiring unit configured to determine coefficients of an adaptive equalizer according to an output signal of the optical communications system; a first transforming unit configured to perform Fourier transform on at least a part of the coefficients of the adaptive equalizer to obtain frequency responses of the at least a part of the coefficients; and a first calculating unit configured to calculate coefficients of the fixed equalizer according to the frequency responses of the at least a part of the coefficients of the adaptive equalizer.

Apparatus and method for determining coefficients of fixed equalizer

Embodiments of this disclosure provide a method and apparatus for establishing a transmission impairment decomposition model for a Raman amplified system and a system. The method includes: converting a Jones vector of a test signal after passing through a Raman amplified system into a Stokes vector; calculating transmission impairments to which the test signal is subjected by using the Stokes vector according to a pre-established transmission impairment decomposition model; and substituting values of the transmission impairments into the pre-established transmission impairment decomposition model to obtain a complete transmission impairment decomposition model used for estimating transmission impairments.

Method and apparatus for establishing transmission impairment decomposition model for Raman amplified system and system

Embodiments of this disclosure provide a method and apparatus for monitoring a modulation depth of a dither signal and an optical transmitter. The apparatus includes a detector to detect an optical signal output by a Mach-Zehnder modulator to obtain an electrical signal, a dither signal at a determined frequency is superimposed on a direct current bias voltage of the Mach-Zehnder modulator; a frequency-doubling dither signal synchronization detection module to perform synchronization detection on the electrical signal and a frequency-doubling dither signal at a frequency twice the determined frequency, to obtain an amplitude of a signal component contained in the electrical signal at a frequency identical to the frequency of the frequency-doubling dither signal A signal processor is to calculate a modulation depth of the dither signal superimposed on the direct current bias voltage according to the amplitude of the signal component at the frequency identical to the frequency of the frequency-doubling dither signal.

Method and apparatus for monitoring modulation depth of dither signal and optical transmitter

A method and apparatus of fiber nonlinear noise monitoring and an optical receiver is provided. The method includes: acquiring a training set including at least two received signal samples obtained after a transmitting signal passes different simulation transmission scenarios, calculating amplitude noise feature values after a digital signal processing, calculating statistics values of fiber nonlinear noises, marking the amplitude noise feature values; taking the amplitude noise feature values as input of a noise monitoring model, taking marks to which the amplitude noise feature values correspond as target output, and training the noise monitoring model according to samples in the training set, so as to obtain a trained noise monitoring model, and inputting a plurality of amplitude noise feature values of received signals to be monitored into the trained noise monitoring model, so as to obtain statistics values of fiber nonlinear noises to which the received signals to be monitored correspond.

Fiber nonlinear noise monitoring method and apparatus and optical receiver

Embodiments of this disclosure provide an apparatus and method for estimating polarization skew. The method includes: acquiring a plurality of coefficients of an adaptive equalizer of a receiving device; the plurality of coefficients of the adaptive equalizer include at least polarization skew of a transmitting device and polarization skew of the receiving device; and calculating the polarization skew of the transmitting device and the polarization skew of the receiving device according to the plurality of coefficients of the adaptive equalizer.

Apparatus and method for estimating polarization skew

An inter-channel linear crosstalk estimation method and apparatus and a communication system are disclosed. The apparatus includes: an adjacent channel synchronizing unit configured to synchronize adjacent channel information inserted with a cyclic training sequence in a received signal, to determine a time window of occurrence of the cyclic training sequence; a time domain cutoff unit configured to perform time cutoff on center channel information in the received signal according to the time window of occurrence of the cyclic training sequence, to obtain center channel information within the same time window as the cyclic training sequence; a filtering unit configured to filter the center channel information within the time window, and reserve center channel information containing linear crosstalk from an adjacent channel; and a linear crosstalk estimating unit configured to estimate a magnitude of linear crosstalk leaking into the center channel by using a cyclic characteristic of the cyclic training sequence.

Inter-channel linear crosstalk estimation method and apparatus and receiver

Embodiments of this disclosure provide an impairment monitoring apparatus, impairment monitoring and compensating system and method. As a parameter of a impairment of a receiver end and/or a parameter of an impairment of a transmitter end is/are determined according to a preset period or a preset condition to perform compensation or calibration, complexity of calculation and power consumption of the system may be efficiently lowered. And as the parameter of the impairment of the receiver end and the parameter of the impairment of the transmitter end are not changed rapidly, determining these parameters according to the preset period or the preset condition to perform compensation or calibration will not affect an effect of the compensation or calibration, thereby ensuring a performance of the system.

Impairment monitoring apparatus, impairment monitoring and compensating system and method

An estimation apparatus for IQ imbalance of an optical transmitter, a compensation apparatus for IQ imbalance of an optical transmitter and electronic equipment; wherein, estimation and compensation of IQ imbalance of an optical transmitter are performed by directly using an estimation model based on a transform matrix of received signals and transmitted signals, therefore, a phase offset shift may be estimated accurately, and precision of estimation of drifts of various angles is ensured, furthermore, accurate recovery of the constellation diagram of received signals is achieved.

Estimation apparatus for IQ imbalance of optical transmitter, compensation apparatus for IQ imbalance of optical transmitter and electronic equipment

A method and apparatus estimating direct current bias of an optical modulator and a receiver. The method includes: performing signal processing to obtain a phase noise compensated signal, extracting a receiving signal component based on the phase noise compensated signal, removing the receiving signal component from the phase noise compensated signal, and calculating a received signal power based on the signal with the receiving signal component being removed. The method includes calculating a direct current bias of the optical modulator based on the receiving signal component, the received signal power and a drive signal power of the optical modulator.

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Beijing, China

Yangyang Fan