Fast least-mean-square (LMS) equalization
AssigneeInfinera Corporation
InventorsAhmed Awadalla, Han Henry Sun, Kuang-Tsan Wu
Life of this patent
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Abstract
Apparatus and methods may provide improved equalizer performance, e.g., for optical-fiber-based communication systems. A least-mean-square (LMS) equalizer may include a decision feedback path containing feedback carrier recovery (FBCR), which may have low latency, and which may thus enable high-speed tap updating in the equalizer. Feed-forward carrier recovery (FFCR) may be applied, in parallel with the FBCR, to provide equalizer output by compensating, e.g., for phase noise, with improved carrier recovery/compensation, versus using FBCR to generate the output.
Claims21
An adaptive equalizer system, including:
- a filter configured to receive input signal samples and provide a filter output, the filter having a plurality of taps having respective tap-weights;
- a tap-weight updating circuit configured to receive the input signal samples and to update one or more of the tap-weights of the filter;
- a switch circuit to receive the filter output;
- a feedback carrier recovery (FBCR) circuit;
- a first feed-forward carrier recovery (FFCR) circuit, the switch circuit selectively supplying the filter output to one of the FBCR circuit and the first FFCR, such that one of the first FFCR circuit and the FBCR circuit receives the filter output and outputs a first phase-error compensated output;
- a decision circuit configured to receive the first phase-compensated output and to provide decision-based output to the tap-weight updater;
- and
- a second feed-forward carrier recovery (FFCR) circuit configured to receive and phase-compensate the filter output to obtain a second phase-error compensated output.
A method of adaptive equalization, including:
- filtering input signal samples to generate filter output;
- updating filter tap-weights of the filtering based at least in part on the input signal samples;
- selectively supplying the filter output to one of a feedback carrier recovery (FBCR) circuit and a first feed-forward carrier recovery (FFCR) circuit;
- processing the filter output by said one of the FBCR circuit and the first FFCR circuit to output first phase-compensated output;
- providing decision-based output based on the first phase-compensated output, and using the decision-based output in the updating filter tap-weights;
- and
- performing feed-forward carrier recovery (FFCR) on the filter output by a second FFCR circuit, in parallel with the processing by said one of the FBCR circuit and the FFCR circuit, to generate equalizer output.
A non-transitory machine-readable medium containing executable instructions configured to cause one or more processing devices to implement operations including:
- filtering input signal samples to generate filter output;
- updating filter tap-weights of the filtering based at least in part on the input signal samples;
- selectively supplying the filter output to one of a feedback carrier recovery (FBCR) circuit and a first feed-forward carrier recovery (FFCR) circuit;
- processing the filter output by said one of the FBCR circuit and the first FFCR circuit to output phase-compensated output;
- providing decision-based output based on the phase-compensated output, and using the decision-based output in the updating tap weights;
- and
- performing feed-forward carrier recovery (FFCR) on the filter output by a second FFCR circuit, in parallel with the processing by said one of the FBCR circuit and the first FFCR circuit, to generate equalizer output.
Dependencies are inferred from the claim text.