Skew Estimator Phase Detector Integrator Coherent Receiver
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Solution Overview
Problem
Coherent optical receivers face challenges in accurately estimating and compensating for skew between data paths, which leads to signal penalties and affects clock recovery performance, especially due to aging, temperature variations, and device switching, within the constraints of sampling intervals and polarization multiplexing.
Innovation Solution
A skew estimator comprising a phase detector and integrator is used to detect and integrate phase signals from multiple data paths, allowing for accurate estimation and compensation of skew, even below the sampling interval, with flexible and robust methods that can be implemented in both hardware and software, and applied before FIR blocks to enhance skew compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If skew estimation is performed using conventional methods, then skew compensation can be achieved, but the estimation accuracy is insufficient for skew values below the sampling interval
Solution Approach 1:
The patent introduces phase detectors as intermediary components that convert skew differences into phase signals. These phase detectors act as mediators between the skewed data paths and the estimation algorithm, enabling precise measurement of sub-sampling-interval skew by transforming temporal delays into detectable phase differences that can be processed by the integrator-based estimator.
Solution Approach 2:
The patent transforms the skew estimation problem from the time domain to the phase domain by using phase detectors. This parameter transformation allows the system to measure skew values smaller than the sampling interval by detecting phase differences rather than direct time delays, effectively changing the measurement parameter from time to phase angle.
2Speed
If skew compensation is implemented in hardware, then real-time compensation is achieved, but the device complexity increases
Solution Approach 1:
The patent replaces complex hardware-based skew compensation mechanisms with a simplified estimation and compensation approach using phase detectors and integrators. This substitution reduces device complexity by eliminating the need for complex hardware equalizers or variable delay lines, while maintaining real-time compensation capability through software or firmware implementation of the estimation algorithm.
3Productivity
If multiple data paths are used for polarization multiplexing, then spectral efficiency is improved, but skew between data paths causes signal penalties
Solution Approach 1:
The patent implements a feedback mechanism where the skew estimator continuously monitors the skew between multiple data paths and provides compensation control signals to align the paths. This feedback loop ensures that skew-induced signal penalties are dynamically compensated, maintaining signal quality while preserving the spectral efficiency benefits of polarization multiplexing.
Solution Approach 2:
The patent segments the skew compensation problem into independent estimators for each data path pair. By dividing the complex multi-path skew compensation into separate, manageable estimation and compensation modules, the system can effectively handle skew in polarization multiplexed systems without compromising signal quality or spectral efficiency.
Data Source
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AI summary
According to the invention, a skew estimator for estimating a skew between a first signal of a first data path and a second signal of a second data path in a coherent receiver is suggested. The skew estimator comprises a phase detector and an integrator. The phase detector is configured to detect a phase of the first signal or the second signal to obtain a phase signal. Further, the integrator is configured to integrate the obtained phase signal to provide an estimated skew.