Sub-sampled Carrier Phase Recovery for Optical Receivers

Solution Overview

Problem

Conventional carrier phase recovery techniques in optical receivers are complex and power-intensive, especially when handling high-bit-rate optical signals using modulation schemes like PM-16-QAM, as they process all received symbols, which is inefficient and consumes significant power.

Innovation Solution

Implementing sub-sampled carrier phase recovery techniques that select a subset of symbols with the highest ratio of measured signal phase error to additive noise for use in carrier phase estimation stages, specifically using Viterbi-Viterbi and Maximum-Likelihood stages, to reduce power consumption while maintaining high performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional carrier phase recovery techniques process all received symbols, then carrier phase estimation accuracy is improved, but power consumption increases significantly

Engineering Contradiction:

Improvecarrier phase estimation accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts only the most informative symbols (those with highest phase error to noise ratio) from the complete symbol stream for carrier phase estimation. This selective extraction maintains estimation accuracy while processing only a subset of symbols, thereby reducing power consumption significantly compared to processing all symbols.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies different processing quality to different symbols based on their local characteristics (phase error to noise ratio). Symbols with higher phase error to noise ratio are selected for processing, while symbols with lower ratios are discarded. This local quality differentiation maintains estimation accuracy for critical symbols while avoiding unnecessary processing of less informative symbols.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If conventional carrier phase recovery techniques process all received symbols, then carrier phase estimation accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvecarrier phase estimation accuracyVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the most informative symbols (those with highest phase error to noise ratio) from the complete symbol stream for carrier phase estimation. This selective extraction maintains estimation accuracy while processing only a subset of symbols, thereby reducing power consumption significantly compared to processing all symbols.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies different processing quality to different symbols based on their local characteristics (phase error to noise ratio). Symbols with higher phase error to noise ratio are selected for processing, while symbols with lower ratios are discarded. This local quality differentiation maintains estimation accuracy for critical symbols while avoiding unnecessary processing of less informative symbols.

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If sub-sampled carrier phase recovery is implemented, then power consumption is reduced, but carrier phase estimation accuracy may deteriorate

Engineering Contradiction:

Improvepower consumptionVSAvoidcarrier phase estimation accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent changes the selection parameter from processing all symbols to processing only symbols with phase error to noise ratio above a threshold. This parameter change enables sub-sampling while maintaining accuracy by ensuring only the most informative symbols are processed. The threshold parameter can be adjusted to balance between power consumption and estimation accuracy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses feedback from phase error measurement and noise ratio estimation to guide symbol selection. By continuously monitoring the phase error to noise ratio and using this feedback to determine which symbols to process, the system adapts its processing behavior to maintain estimation accuracy while minimizing power consumption.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9270384B2Sub-sampled carrier phase recovery

Publication Date: 2016.02.23 CISCO TECHNOLOGY INC

AI summary

Presented herein are sub-sampled carrier phase recovery techniques. In accordance with one example, a plurality of consecutive symbols associated with a received optical signal is obtained. Carrier phase recovery of the optical signal is performed using one or more carrier phase estimation stages. At each of the one or more carrier phase estimation stages, a subset of the plurality of consecutive symbols is selected for use in carrier phase estimation. The subset of symbols selected for use in carrier phase estimation at each of the one or more stages comprises symbols that provide the most phase recovery information for each of the one or more stages.