Embodiments of the present disclosure relate to a device, a method, an apparatus and a computer-readable medium for signal equalization. According to the embodiments of the present disclosure, a balance between equalization performance and effects is achieved by using a linear equalizer and a nonlinear equalizer. In addition, signals from different uplinks are equalized using adaptive parameters, to achieve optimal equalization of various signals.

The disclosed structures and methods are directed to a method for compensation of linear and nonlinear effects in optical fiber of a coherent optical signal transmitted through an optical link. The method comprises receiving a coherent optical signal having carriers; determining values of intensity vectors for each carrier; determining values of filtered intensity vectors for each carrier by filtering the values of the intensity vectors at frequencies lower than a cut-off frequency of a filter; determining nonlinear compensation coefficients for each carrier based on the filtered intensity vectors; and modifying the digital coherent optical signal based on the nonlinear compensation coefficients.

A method facilitates determining transmission loss in a transmission signal and adjusting a receiver setting of a receiver to compensate for the transmission loss. The method includes transmitting a transmission signal from a transmitter and receiving the transmission signal by a first receiver and a second receiver. The method includes digitizing the transmission signal by the first receiver at a first sampling frequency and digitizing the transmission signal by the second receiver at a second sampling frequency that is less than or equal to the first sampling frequency. The method includes generating a PAM-n eye diagram of the transmission signal by the second receiver using digitized signals digitized by the first and second receivers and adjusting an equalizer setting of a first equalizer of the first receiver using eye-opening information of the PAM-n eye diagram where the eye-opening information includes information for the transmission loss.

An illustrative SerDes receiver includes: a front-end filter, a precomputation unit, a selection element, and a controller. The front end filter converts a receive signal into a linearly-equalized signal. The precomputation unit accepts the linearly-equalized signal with or without a subtracted feedback signal, and employs a set of comparators with threshold values that depend on a first post-cursor ISI value F.sub.1, the set of comparators operating to generate a set of tentative symbol decisions. The selection element derives a selected symbol decision from each set of tentative symbol decisions, thereby deriving a sequence of symbol decisions from the receive signal. The controller constrains F.sub.1 if the receive signal uses a PAM4 signal constellation, setting F.sub.1 to equal zero if the receive signal is conveyed via a low-loss channel and to equal one if the receive signal is conveyed via a high-loss channel.

A radio frequency (RF) photonic equalizer may include a first electro-optic (E/O) modulator configured to modulate an optical carrier based upon an RF input signal, a stimulated Brillouin scattering (SBS) medium coupled to the first E/O modulator, and a second E/O modulator configured to modulate the optical carrier based upon an equalizing function waveform. An optical circulator may be coupled to the SBS medium and the second E/O modulator, and a photodetector may be coupled to the optical circulator.

A circuit and method for mitigating multi-path interference in direct detection optical systems is provided. Samples of an optical signal having a pulse amplitude modulated (PAM) E-field are processed by generating a PAM level for each sample. For each sample, the sample is subtracted from the respective PAM level to generate a corresponding error sample. The error samples are lowpass filtered to produce estimates of multi-path interference (MPI). For each sample, one of the estimates of MPI is combined with the sample to produce an interference-mitigated sample.

Per-port performance optimization may be provided. First, performance data may be received corresponding to each of a plurality of ports. Then it may be determined that performance of at least one of the plurality of ports can be improved based on the received performance data corresponding to the least one of the plurality of ports. Next, in response to determining that the performance of the at least one of the plurality of ports can be improved, at least one of a plurality of components may be adjusted corresponding to the at least one of the plurality of ports to improve performance of the least one of the plurality of ports.

The present disclosure provides a non-linear receiver, an asymmetric decision feedback equalization circuit and method, including: converting an optical signal emitted by a laser device into an electrical signal; obtaining a compensation amplitude of a current data in the electrical signal by obtaining an actual amplitude of the current data, and compensating the current data based on a logic value of k prior data of the current data and a feedback coefficient corresponding to the prior data; comparing the compensation amplitude of the current data with a decision threshold to determine the logic value of the current data; the feedback coefficient is an absolute value of an influence amount of the prior data on an amplitude of the current data, and k is a positive integer. The present disclosure can overcome the bit error problem of the receiver and reduce jitter of the clock recovered by the clock recovery circuit.

A symbol-determining device according to an embodiment includes: a transmission line shortening unit that multiplies each symbol value of a symbol array that is part of an input signal by a tap gain of a linear digital filter and outputs a symbol array representing a sum of values acquired through the multiplication; a transmission line estimating unit that estimates a transfer function of a transmission line using an adaptive nonlinear digital filter on the basis of a symbol array representing a state of the transmission line; an addition comparison processing unit that calculates a minimum value of a distance function in a Viterbi algorithm on the basis of a metric that is calculated on the basis of the output of the transmission line shortening unit and the transfer function; and a path tracing-back determination unit that performs symbol determination by tracing back a trellis path in the Viterbi algorithm on the basis of the minimum value of the distance function.

The disclosed structures and methods are directed to a method for compensation of linear and nonlinear effects in optical fiber of a coherent optical signal transmitted through an optical link. The method comprises receiving a coherent optical signal having carriers; determining values of intensity vectors for each carrier; determining values of filtered intensity vectors for each carrier by filtering the values of the intensity vectors at frequencies lower than a cut-off frequency of a filter; determining nonlinear compensation coefficients for each carrier based on the filtered intensity vectors; and modifying the digital coherent optical signal based on the nonlinear compensation coefficients.