Phase Estimator Architecture for Optical Signal Phase Slip Detection

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Solution Overview

Problem

Current carrier phase recovery schemes in optical communications suffer from phase slips due to phase noise, leading to erroneous data detection and increased implementation complexity, especially at high data rates, as they require differential encoding or high pilot symbol rates to track phase noise effectively.

Innovation Solution

A phase estimator architecture that employs a pilot-based phase slip detection scheme, allowing for low pilot rates while using blind phase estimation for fast tracking, enabling absolute phase detection without differential encoding and providing an analytical description of residual phase errors based on receiver SNR and link probability of phase slips.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If blind phase estimation is used for fast tracking, then phase tracking speed is improved, but phase slips occur leading to erroneous detection

Engineering Contradiction:

Improvephase tracking speedVSAvoiddetection accuracy

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent introduces pilot symbols as an intermediary reference signal between the transmitter and receiver. These pilot symbols carry known phase information that mediates the phase tracking process, allowing the receiver to detect and correct phase slips that occur during blind phase estimation, thereby maintaining both fast tracking and reliable detection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a feedback mechanism where the receiver detects phase slips by comparing received pilot symbols with expected pilot symbols, then feeds back phase correction information to adjust the phase tracking. This closed-loop feedback system enables the receiver to maintain accurate phase detection even when blind phase estimation causes temporary phase slips

Inventive Principle:

Principle #23Feedback

2Reliability

If differential encoding is used to avoid phase slips, then detection reliability is improved, but implementation complexity increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidimplementation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the phase reference information from the data symbols themselves by introducing separate pilot symbols. This separation allows the system to maintain absolute phase detection without requiring differential encoding, thereby reducing implementation complexity while preserving detection reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using differential encoding to make the system robust against phase slips (the conventional approach), the patent inverts the approach by using pilot symbols to actively detect and correct phase slips, enabling the use of simpler absolute phase detection schemes

Inventive Principle:

Principle #13The other way round (Inversion)

3Measurement precision

If high pilot symbol rate is used to track phase noise, then phase tracking accuracy is improved, but data rate efficiency decreases

Engineering Contradiction:

Improvephase tracking accuracyVSAvoiddata rate efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies partial action by using pilot symbols at a reduced rate rather than continuously. The pilot symbols are transmitted periodically at low rates (e.g., 1/4 to 1/16 of the data symbol rate), which is sufficient to detect phase slips without significantly reducing data rate efficiency, while still maintaining adequate phase tracking accuracy

Inventive Principle:

Principle #16Partial or excessive action

4Productivity

If low pilot rate is used, then data rate efficiency is improved, but phase slip detection capability deteriorates

Engineering Contradiction:

Improvedata rate efficiencyVSAvoidphase slip detection capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the parameters of the pilot symbols to optimize their effectiveness at low rates. Specifically, it adjusts the pilot symbol density, positioning, and processing algorithms to maximize phase slip detection capability while minimizing the impact on data rate efficiency. The system adapts parameters such as pilot spacing and detection threshold based on channel conditions

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2806584B1Apparatus, method and computer program for recovering a phase of a received signal

Publication Date: 2020.03.04 ALCATEL LUCENT SA

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AI summary

Embodiments relate to an apparatus (100; 300; 400; 500; 600) for recovering a phase of a received signal (Sin) carrying pilot and information symbols, wherein the received signal has been transmitted over a communication channel (200), the apparatus comprising a phase estimator (110) operable to determine a phase estimate (115) of a phase of the communication channel using the received signal, wherein the phase estimator (110) commits a phase slip with a phase slip probability (PS, PT) depending on the communication channel (200); a demodulator (120) operable to determine demodulated pilot and information symbols (125) based on a coherent reception of the received pilot and information symbols using the determined phase estimate (115); a phase slip detector (130; 330; 430; 530; 630) operable to detect the phase slip based on a phase difference between at least one demodulated pilot symbol and at least one corresponding transmitted pilot symbol; and a phase corrector (140; 340; 440; 540) operable to correct a phase of demodulated information symbols based on the detected phase slip.