Digital Coherent Receiver Adaptive Equalization Polarization Fluctuation
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Solution Overview
Problem
Conventional digital coherent receivers face performance degradation when the state of polarization of a polarization-multiplexed signal fluctuates rapidly, as they struggle to keep up with these changes in polarization state, leading to increased bit error rates.
Innovation Solution
A digital coherent receiver is designed with an adaptive equalizer and a coefficient updating unit that adjusts the tap coefficients and step sizes based on the fluctuation speed of the state of polarization, switching to a larger step size when the fluctuation exceeds a threshold to maintain reception performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed step size is used in the adaptive equalizer, then the system is simple to implement, but the reception performance degrades when the state of polarization fluctuates rapidly
Solution Approach 1:
The patent implements dynamic step size adjustment in the adaptive equalizer based on detected polarization fluctuation speed. The step size parameter is changed from fixed to variable, allowing the system to adapt to different polarization fluctuation conditions. When fluctuation speed exceeds a threshold, a larger step size is used to track rapid changes; when below the threshold, a smaller step size maintains stability. This dynamic adjustment resolves the contradiction by improving reception performance during rapid fluctuations while maintaining manageable system complexity through automated control.
Solution Approach 2:
The patent changes the step size parameter of the adaptive equalizer based on the detected fluctuation speed of the state of polarization. By monitoring polarization characteristics and adjusting the step size parameter accordingly, the system optimizes its ability to track polarization changes. This parameter change approach allows the equalizer to maintain high reception performance across varying polarization conditions without requiring overly complex structural modifications.
2Speed
If the step size is increased to track rapid polarization fluctuations, then the ability to follow SOP changes improves, but the stability of the equalization processing deteriorates
Solution Approach 1:
The system dynamically adjusts the step size based on real-time detection of polarization fluctuation speed. When the fluctuation speed exceeds a predetermined threshold, the step size is increased to enable rapid tracking. When below the threshold, the step size is reduced to maintain processing stability. This dynamic control mechanism resolves the contradiction by allowing the system to switch between speed and stability modes as needed, rather than being fixed in one state.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the state of polarization and using this information to adjust the step size parameter. The detected fluctuation speed feeds back into the control decision process, creating a closed-loop system that automatically balances tracking speed and processing stability. This feedback mechanism ensures that large step sizes are only used when necessary for tracking rapid changes, thereby maintaining overall system stability.
3Reliability
If digital signal processing operates at high speed to keep up with rapid SOP changes, then the reception performance is maintained, but the processing complexity increases
Solution Approach 1:
The patent optimizes digital signal processing by dynamically changing the step size parameter of the adaptive equalizer based on polarization fluctuation characteristics. This parameter adjustment allows the system to maintain reception performance during rapid SOP changes without proportionally increasing processing complexity. The control unit monitors polarization state and adjusts processing parameters accordingly, achieving high reception reliability while keeping the digital signal processing complexity manageable through intelligent parameter control rather than brute-force processing power.
Data Source
AI summary
A digital coherent receiver includes: an adaptive equalizer configured to execute, using a first tap coefficient, adaptive equalization processing on a digital signal that corresponds to a signal; a first coefficient updating unit configured to update the first tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a first step size; a second coefficient updating unit configured to update a second tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a second step size; and a control unit configured to detect a fluctuation speed of a state of polarization of the digital signal based on the second tap coefficient, and change the first tap coefficient to the updated second tap coefficient if it is determined that the fluctuation speed is higher than or equal to a speed threshold.