A method to process applicable to coherent optical channels with either linear or nonlinear phase noise includes: splitting a received sequence of data into clusters of points according to a cumulative log-likelihood function from constellation obtained in a previous iteration; generating new constellation points by calculating a center of mass of the clusters of points; repeating until convergence or until a predetermined number of iterations has been reached to determine a signal constellation; and transmitting signals over the coherent optical channels with nonlinear phase noise using the disclosed signal constellation and LDPC-coded modulation concepts.

We disclose an optical transport system configured to reduce nonlinear signal distortions using an electronic phase rotation, the phase value of which is determined using pre-filtering, e.g., via a low-pass filter, of the digital samples representing an optical communication signal prior to applying a squaring operation to the digital samples. In some embodiments, the phase value used in the electronic phase rotation can be determined using double filtering of the digital samples that, in addition to the pre-filtering, employs post-filtering, e.g., via another low-pass filter, of the digital samples generated by the squaring operation. The electronic phase rotation can be implemented as part of a backward-propagation algorithm that, in addition to reducing the nonlinear signal distortions, provides at least partial dispersion compensation. In various embodiments, the corresponding backward-propagation module can be incorporated into the transmitter's digital signal processor (DSP) or the receiver's DSP.

The reception (102) reception unit includes; a first processing unit processing a first signal received from a source channel, and including a filtering unit to filter said first signal in digital domain, and extract unit to extract a information from said first signal; a second processing unit processing a second signal received from a destination channel, and said source channel and said destination channel are distinct each other; a third processing unit providing said information extracted from said first signal to said second signal said third processing unit executes; providing said information from said first processing unit to said second processing unit using information lanes of a clock rate strictly lower than a symbol rate of said second signal, a monitoring unit to generate a monitor signal according to the quality of said second signal; and a control unit controlling a skew between said first signal and said second signal in a bandwidth of said filtering units in said first processing unit.

Disclosed are a chromatic dispersion estimation method and device in optical coherent communication, wherein, the method includes: performing a fast Fourier transform on IQ-imbalance compensated data to obtain frequency-domain data in two polarization directions; calculating autocorrelation sequences of the frequency-domain data and performing an inverse fast Fourier transform on the values of the autocorrelation sequences; calculating modulus squares of the results of the inverse fast Fourier transform, and adding the results in the two polarization directions to obtain; determining a mean value of s of a plurality of data sets; calculating an index of the maximum value of, and estimating a dispersion value of the optical fiber link according to the index of the maximum value of. The abovementioned technical solution allows a significantly accurate and rapid estimation of dispersion values.

An optical wireless apparatus that is implemented for transmitting an optical wireless signal via an optical wireless channel includes: an electronic signal source that is configured to provide a data signal and an optical signal source that is configured to convert the data signal into the optical wireless and to emit the same. The optical wireless apparatus is configured to obtain channel information including information associated with a non-linear channel distortion of the optical wireless signal and to perform adaptation of a modulation of the optical signal source by changing an operating state of the electronic signal source for adapting the non-linear channel distortion and/or to perform adaptation of an operating point of the optical signal source for adapting the non-linear channel distortion.

A method of controlling a parameter in the generation of a coherent optical signal, the method comprising the steps of: receiving a set of signal samples relating to detection of a coherent optical signal; transforming the set of signal samples into a set of spectrum samples in the frequency domain, the set of spectrum samples being an estimation of the spectrum of the coherent optical signal; calculating at least one feedback variable based on the spectrum samples; and adjusting the parameter based on the at least one feedback variable.

In order to stabilize the characteristics of reception of an optical signal received via a transfer path, this optical receiver is provided with: a local beam output means 1; a light receiving means 2; a photoelectric conversion means 3; a measuring means 4; a control means 5; and a comparing means 6, the comparing means 6, when the control means 5 sweeping the wavelength of the local beam in a predetermined wavelength range with respect to the central wavelength of the optical signal, generating difference data between a spectrum based on a result of the measuring, by the measuring means 4, of the electric signal in accordance with a change in the wavelength of the local beam and a preset reference spectrum.

An optical transport system configured to compensate nonlinear signal distortions using a backward-propagation algorithm in which some effects of polarization mode dispersion on the nonlinear signal distortions are accounted for by employing two or more different approximations of said effects within the bandwidth of the optical communication signal. In an example embodiment, the corresponding digital signal processor (DSP) is configured to switch between different approximations based on a comparison, with a fixed threshold value, of a difference between frequencies of various optical waves contributing to the nonlinear signal distortions, e.g., through four-wave-mixing processes. In different embodiments, the backward-propagation algorithm can be executed by the transmitter's DSP or the receiver's DSP.

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.

The disclosure relates to a method, an optical receiver and an optical system for compensating, at an optical receiver, signal distortions induced in an optical carrier signal by a periodic copropagating optical signal, wherein the optical carrier signal and the copropagating signal copropagate at least in part of an optical system or network, by: receiving, at the optical receiver, the optical carrier signal, wherein the optical carrier signal is distorted by the copropagating signal; determining, at the optical receiver, a period of a periodic component of the distorted optical carrier signal; determining, at the optical receiver, a periodic distortion of the distorted optical carrier signal; and generating a compensation signal to correct the distorted optical carrier signal according to the determined periodic distortion.