Limiter-Based Phase Correction for Coherent DWDM Systems
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Solution Overview
Problem
In coherent dense wavelength division multiplexing systems, the presence of intensity-modulated signals can cause non-linear cross-phase modulation in phase-modulated signals, leading to phase errors and impairing data recovery, especially at high data rates, and existing methods to mitigate this often reduce data capacity or result in cycle slips.
Innovation Solution
A method and system that estimate phase errors in a series of symbols and apply a phase correction to subsequent symbols, with a limiter ensuring the correction does not exceed a maximum value to prevent cycle slips, thereby maintaining data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase correction is applied to mitigate non-linear cross-phase modulation, then data recovery accuracy is improved, but cycle slips may occur when correction exceeds maximum values
Solution Approach 1:
The system dynamically adjusts phase correction values based on estimated phase errors, applying corrections adaptively to each symbol while maintaining a maximum limit threshold. This dynamic approach allows the system to respond to varying phase conditions without exceeding safe correction boundaries that could cause cycle slips.
Solution Approach 2:
The system uses feedback from detected phase errors to continuously adjust phase corrections. By monitoring the phase error estimates and comparing them against maximum correction thresholds, the system provides feedback control that prevents over-correction while maintaining accurate phase alignment for data recovery.
2Measurement precision
If aggressive phase correction is applied to eliminate phase errors, then data recovery accuracy is improved, but data capacity is reduced
Solution Approach 1:
The system applies partial phase correction by limiting the correction magnitude to a maximum value, using only the necessary portion of correction needed to prevent cycle slips while avoiding excessive correction that would reduce data capacity. This partial action approach maintains the optimal balance between correction effectiveness and capacity preservation.
3Measurement precision
If phase correction without limiting is applied, then phase errors are fully corrected, but cycle slips occur reducing reliability
Solution Approach 1:
The system implements beforehand cushioning by establishing a maximum phase correction limit threshold before cycle slips can occur. This pre-set boundary acts as a protective cushion that prevents over-correction and potential cycle slips, ensuring data stream continuity while still providing effective phase error correction within safe limits.
Data Source
AI summary
Various example embodiments are disclosed. According to one example embodiment, a phase error is estimated in a series of digital symbols of a phase-modulated signal, where the signal is subject to a non-linear phase shift error due to transmission of the signal through an optical fiber. A phase correction of an instant digital symbol that succeeds the series of digital symbols is estimated, where the estimated phase correction is based on the estimated phase errors in the series of digital symbols. The estimated phase correction of the instant digital symbol is limited to a maximum absolute value, and the estimated phase correction is applied to the instant digital symbol of the signal.