Optical Receiver Sampling Phase Selection

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Solution Overview

Problem

Optical receivers face challenges in compensating for chromatic dispersion in optical transmission systems, particularly in shorter links without dispersion compensating fibers, leading to noise, nonlinear effects, and high power requirements, and existing equalization techniques struggle to optimize sampling phases for improved performance.

Innovation Solution

A sampling phase estimator is used to determine the optimal sampling phase for an MLSE equalizer by calculating a sampling phase quality indicator (SPQI) through branch metric calculations and interpolation, adjusting the sampling phase to improve equalization performance and reduce bit error rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dispersion compensating fibers (DCF) are used to correct chromatic dispersion, then signal quality is improved, but noise increases and power requirements increase

Engineering Contradiction:

Improvesignal qualityVSAvoidnoise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical/optical dispersion compensation system (DCF) with a digital signal processing system. The DFE equalizer performs chromatic dispersion compensation through electrical/digital processing of the received signal, eliminating the need for physical dispersion compensating fibers and their associated noise and power issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If dispersion compensating fibers (DCF) are used to correct chromatic dispersion, then signal quality is improved, but power requirements increase

Engineering Contradiction:

Improvesignal qualityVSAvoidpower requirements

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent substitutes the high-power optical dispersion compensating fibers with a low-power digital signal processing approach. The DFE equalizer operates in the electrical domain using standard electronic components, dramatically reducing power consumption compared to optical DCF systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If sampling phase is not optimized, then system complexity is reduced, but bit error rate increases

Engineering Contradiction:

Improvesystem complexityVSAvoidbit error rate

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The DFE equalizer automatically adapts its sampling phase through self-adjustment mechanisms. The equalizer monitors the received signal quality and autonomously optimizes the sampling phase without requiring external intervention or complex additional circuitry, achieving low BER while maintaining simple system architecture.

Inventive Principle:

Principle #25Self-service

4Manufacturing precision

If automatic gain control is used to adjust signal levels, then signal clipping is prevented, but noise is introduced

Engineering Contradiction:

Improvesignal level controlVSAvoidnoise

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the analog automatic gain control system with a digital gain control mechanism implemented in the DFE equalizer. The digital processing adjusts signal levels after conversion, avoiding the noise introduction inherent in analog AGC circuits while maintaining precise signal level control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The proposed method enhances the performance of optical receivers by optimizing sampling phases, leading to reduced bit error rates and improved compensation for chromatic dispersion, even in severely distorted channels without the need for expensive coherent detection systems.

Implementation Method 1

a photo diode (PD) may detect the optical signal, with the output of the photo diode substantially proportional to the optical signal power

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentEP3248307B1Sampling phase selection in an optical receiver

Publication Date: 2019.04.10 HUAWEI TECH CO LTD

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AI summary

Disclosed is a method of selecting a sampling phase in an optical receiver, the method includes estimating a plurality of sampling phase quality indicator (SPQI) values for a plurality of adjusted sampling phases within or more unit intervals in a received signal. The method additionally includes selecting from the plurality of SPQI values the SPQI with the highest value. Also disclosed is an equalization circuit including an equalizer to equalize a received signal, and a best sampling phase estimator (BSPE) 30 to estimate a plurality of sampling phase quality indicator (SPQI) values for a plurality of adjusted sampling phases within one or more unit intervals in said received signal. The BSPE 30 additionally selects from the plurality of SPQI values the SPQI with the highest value.