Phase Detector Correlation for Clock Recovery in Coherent Light Communication
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Solution Overview
Problem
Conventional phase detectors in coherent light communication systems face significant errors in phase detection signals due to factors like random polarization rotation, polarization-dependent loss, and chromatic dispersion, leading to inaccurate sampling rates in clock recovery circuits.
Innovation Solution
A method where a phase detector calculates correlations between sampling sequences and a comparison sequence generated based on a training sequence and target sampling rate to determine the locations of the training sequence, thereby obtaining a phase detection signal without relying on waveform calculations, thus mitigating the impact of system impairments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional phase detector calculates phase detection signal based on waveform, then the phase detection signal can be obtained, but the error is relatively large due to factors like polarization rotation, polarization-dependent loss, polarization mode dispersion, chromatic dispersion, channel bandwidth impairment, and frequency offset
Solution Approach 1:
The patent extracts the training sequence from the received signal and uses it as a reference for correlation calculation. By focusing only on the known training sequence rather than the entire distorted waveform, the method eliminates the impact of various channel impairments on phase detection accuracy
Solution Approach 2:
The patent creates a local copy of the training sequence at the receiver side and uses it for correlation calculation with the received training sequence. This copying approach allows direct comparison without being affected by channel distortions, thereby achieving accurate phase detection
2Reliability
If waveform-based calculation is used in phase detector, then phase detection signal can be generated, but the correctness is compromised under coherent light communication conditions
Solution Approach 1:
The patent replaces the mechanical waveform-based calculation approach with a correlation-based mathematical operation. Instead of analyzing the entire waveform shape and characteristics, the method uses simple correlation calculation between the local training sequence copy and received training sequence, reducing computational complexity while improving reliability
Data Source
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AI summary
Embodiments of this application provide a method for obtaining a phase detection signal in a clock recovery circuit and a phase detector, configured to obtain a correct phase detection signal. A technical solution provided in the embodiments of this application is as follows: A phase detector obtains sampling sequences sent by an analog to digital converter ADC, where the sampling sequences are obtained by the ADC by sampling, based on an actual sampling rate, an electrical signal received by the ADC, and the electrical signal carries a pre-configured training sequence; the phase detector calculates a correlation between the sampling sequences and a comparison sequence, to determine a first location and a second location, where the first location and the second location are locations of a starting point of the training sequence in the sampling sequences, there is a difference of M1 training sequence periods (where M1 is a positive integer) between the first location and the second location in starting points of the sampling sequences, and the comparison sequence is generated by the phase detector based on the training sequence and a target sampling rate of the ADC; and the phase detector obtains a phase detection signal based on a difference parameter of the first location and the second location.