Described herein are systems and methods that perform coarse chromatic dispersion (CD) compensation by applying precomputed coarse front-end equalizer (FEE) tap weights to a receiver based on an assumed propagation distance. After a waiting period, the FEE tap weights are applied, and it is determined whether the FEE tap weights cause a decision-directed tracking of channel rotations to satisfy a stability metric. In response to the stability metric not being satisfied, the assumed propagation distance is adjusted and used to obtain updated FEE tap weights. Conversely, if the stability metric is satisfied, a fine CD compensation is performed that comprises maintaining the updated FEE tap weights; performing an iterative least-mean-squared (LMS) error adaption to adjust Back-End Equalizer (BEE) tap weights and obtain updated BEE tap weights; and using the updated BEE tap weights to adjust the FEE tap weights to, ultimately, have the BEE output an equalized data bit stream.

Disclosed embodiments include a decision feedback equalizer (DFE) comprising an N-bit parallel input adapted to be coupled to a communication channel and configured to receive consecutive communication symbols, a first DFE path including a first path input configured to receive communication symbols, and a first adder having a first adder input coupled to the first path input. There is a first DFE filter having outputs responsive to the first DFE filter inputs, the outputs coupled to the second adder input. The DFE includes a first path having a first slicer and a first multiplexer, a first path multiplexer output, and a second DFE path including a second path input configured to receive a second communication symbol, a second adder, a second DFE filter, a second slicer, and a second multiplexer.

A receiver receives communications over a communication channel, which may distort an incoming communication signal. In order to counter this distortion, the frequency response of the receiver is manipulated by adjusting several frequency response parameters. Each frequency response parameter controls at least a portion of the frequency response of the receiver. The optimal values for the frequency response parameters are determined by modifying an initial set of values for the frequency response parameters through one or more of stochastic hill climbing operations until a performance metric associated with the receiver reaches a local maximum. The modified values are displaced through one or more mutation operations. The stochastic hill climbing operations may subsequently be performed on the mutated values to generate the final values for the frequency response parameters.

A device and method for a receiver configured to perform timing recovery decoupled feed-forward equalizer (FFE) adaptation. The receiver device can include an analog front-end (AFE) device, which is coupled to a time-interleaved (TI) interface. The TI interface is coupled in a timing recovery feedback loop to FFE equalizers, a digital signal processor (DSP), a delay timing loop (DTL) device, and a clock device, which feeds back to the TI interface. The DSP has an additional pathway to the FFE equalizers, which has an additional pathway to the DTL device. The DTL loop is equipped with an interleave specific enable/disable vector Q[1:N] that can turn on/off the contribution of the specific time interleave errors to the timing recovery loop, which allows the FFE adaptation process to be decoupled from the timing recovery loop.

A method and apparatus for adapting an equalizer coefficients to a channel comprising filtering a high frequency error monitor slicer output and a data slicer output to isolate selected high frequency symbol values. Filtering a low frequency error monitor slicer output and the data slicer output to isolate selected low frequency symbol values. Generating a high frequency error monitor slicer threshold signal with a first adaptation module. Generating a low frequency error monitor slicer threshold signal with the first adaptation module or a second adaption module. Combining the high frequency error monitor slicer threshold signal and the low frequency error monitor slicer threshold signal to generate a difference signal. Integrating the difference signal with an accumulator to generate equalizer coefficients to adapt the equalizer to the channel. Providing the high frequency and low frequency error monitor slicer threshold signal to respective slicers.

In described examples of a signal equalizer, a complex signal having a first signal component and a second signal component is received from a communication channel. Adaptive equalization of crosstalk between the first signal component and the second signal component is performed using a single complex tap of a feedforward equalizer. A feedforward filter with real only taps converts the channel into a minimum phase channel that has postcursor interference only so that a low complexity decision feedback filter with all complex taps can easily eliminate the postcursor interreference.

A network transceiver device is provided, including at least two variable gain amplifiers (VGAs), and at least two sets of analog digital converters (ADCs), each set including ADCs coupled to an output of one of the VGAs, the sets being arranged in VGA-specific channels. The device includes a plurality of feed-forward equalizers (FFEs), each FFE being coupled to receive an output of one of the ADCs in one of the VGA-specific channels. Each FFE is configured to adaptively equalize the output received from the ADCs utilizing a first equalization coefficient subset with coefficient values that are common to all FFEs, and a second equalization coefficient subset that is channel specific and that has a first set of coefficient values for a first VGA-specific channel and a second set of coefficient values for a second VGA-specific channel, the sets of coefficient values being computed independently.

An error sampler circuit includes a differential input voltage input, a differential reference voltage input, a master latch circuit, and a slave latch circuit. The master latch circuit includes a slicer circuit. The slicer circuit includes a first input, a second input, and a differential output. The first input is coupled to the differential input voltage input. The second input is coupled to the differential reference voltage input. The slave latch includes a differential input coupled to the differential output of the slicer circuit.

A method and structure for equalization in coherent optical receivers. Block-based LMS (BLMS) algorithm is one of the many efficient adaptive equalization algorithms used to (i) increase convergence speed and (ii) reduce implementation complexity. Since the computation of the equalizer output and the gradient of the error are obtained using a linear convolution, BLMS can be efficiently implemented in the frequency domain with the constrained frequency-domain BLMS (FBLMS) adaptive algorithm. The present invention introduces a novel reduced complexity constrained FBLMS algorithm. This new approach replaces the two discrete Fourier transform (DFT) stages required to evaluate the DFT of the gradient error, by a simple frequency domain filtering. Implementation complexity can be drastically reduced in comparison to the standard constrained FBLMS. Furthermore, the new approach achieves better performance than that obtained with the unconstrained FBLMS in ultra-high speed coherent optical receivers.

A decision feedback equalizer for generating an output signal according to an input signal includes: a feedforward equalizer, a feedback equalizer and a weight coefficient control unit. The feedforward equalizer includes a plurality of tapped delay lines and is controlled by a set of first weight coefficients. The feedback equalizer includes a plurality of tapped delay line and is controlled by a set of second weight coefficients. The weight coefficient control unit is employed to selectively adjust at least one of the set of first weight coefficients and determine a set of first boundary values for at least one of the set of second weight coefficients. When the at least one of the set of second weight coefficients does not exceed the set of first boundary values, the weight coefficient control unit increments the at least one of the set of first weight coefficients.