Polarization-Multiplexed Signal Processing for Adaptive Equalizer Convergence
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Solution Overview
Problem
Conventional adaptive equalizer configurations for high-order multi-level signals face complexity and convergence issues in equalization processing, leading to slow adaptation and potential oscillation or divergence during distortion compensation, especially when dealing with large distortion components in transmitters.
Innovation Solution
A signal processing method involving convolution of real and imaginary components of polarization-multiplexed signals with impulse responses for frequency and wavelength dispersion compensation, followed by phase rotation and addition/subtraction of transmission data bias correction signals, dynamically updating complex impulse responses for improved compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-stage configuration of adaptive equalizer is employed to compensate for time-varying waveform distortion factors, then compensation accuracy is improved, but processing complexity increases and convergence speed decreases
Solution Approach 1:
The patent segments the equalization process into two distinct stages: a first adaptive equalizer for initial convergence and a second adaptive equalizer for fine-tuning. This segmentation allows each equalizer to specialize in specific aspects of distortion compensation, improving overall accuracy while managing complexity through functional division.
Solution Approach 2:
The first adaptive equalizer performs preliminary compensation for time-varying waveform distortion factors before the second adaptive equalizer refines the compensation. This preliminary action enables the system to achieve basic convergence quickly, reducing the burden on the second equalizer and accelerating overall convergence speed.
2Measurement precision
If a multi-stage configuration of adaptive equalizer is employed to compensate for time-varying waveform distortion factors, then compensation accuracy is improved, but adaptation operation complexity increases
Solution Approach 1:
The patent divides the adaptation operation into two separate control loops: one for the first adaptive equalizer and another for the second adaptive equalizer. This segmentation simplifies the adaptation operation by allowing each equalizer to be controlled independently with its own optimization algorithm, reducing the overall operational complexity despite improved accuracy.
3Measurement precision
If conventional equalizer configuration is used, then receiver IQ imbalance and skew are compensated, but transmitter IQ imbalance and skew cannot be compensated
Solution Approach 1:
The patent designs the multi-stage adaptive equalizer system to perform multiple functions: it compensates for both receiver impairments (IQ imbalance and skew) and transmitter impairments (IQ imbalance and skew). The first and second adaptive equalizers work together to provide universal compensation capability for all major signal distortions in the transmission system.
4Measurement precision
If large distortion component in transmitter is present, then compensation is needed, but adaptive equalization oscillates or diverges
Solution Approach 1:
The first adaptive equalizer performs preliminary compensation for large distortion components in the transmitter, reducing the magnitude of distortions before they reach the second adaptive equalizer. This preliminary action prevents the second equalizer from encountering large distortions that would cause oscillation or divergence, thereby maintaining equalization stability.
Solution Approach 2:
The patent implements a cushioning effect by having the first adaptive equalizer absorb and mitigate large distortion components before they can destabilize the second adaptive equalizer. This beforehand cushioning protects the fine-tuning stage from harmful large-amplitude distortions, ensuring stable convergence even when significant transmitter distortions are present.
Data Source
AI summary
A receiver convolutes each of a real component and an imaginary component of each polarization of a polarization-multiplexed reception signal with an impulse response for compensating for frequency characteristics of the receiver and a complex impulse response for wavelength dispersion compensation, and generates, as input signals, the convoluted real component and imaginary component of each polarization and phase conjugations thereof, for each polarization. The receiver generates, for each polarization, a first addition signal obtained by multiplying each of the real component and the imaginary component of each polarization by a complex impulse response, thereafter adding together the multiplied real component and imaginary component, and applying a phase rotation for frequency offset compensation to the added components, and a second addition signal obtained by multiplying each of the phase conjugation of the real component of and the phase conjugation of the imaginary component of each polarization by a complex impulse response, thereafter adding together the multiplied phase conjugations, and applying a phase rotation opposite to the phase rotation for frequency offset compensation to the added phase conjugations, and adds or subtracts a transmission data bias correction signal to or from a signal obtained by adding together the generated first addition signal and second addition signal.