Adaptive Equalizer Tap Coefficient Shifting for Optical Signal Stability
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Solution Overview
Problem
High-bit-rate optical communication systems face signal quality degradation due to OSNR performance and waveform distortion caused by wavelength dispersion, polarization mode dispersion, and nonlinear effects, which existing technologies struggle to address effectively, especially in maintaining stable equalization during initial training and communications.
Innovation Solution
An adaptive equalizer with a finite impulse response filter and a tap coefficient adaptive controller that calculates and shifts tap coefficients based on a weighted center to minimize differences with the tap center, ensuring symmetry and stability during both initial training and communications, even with changing propagation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of taps in the finite impulse response filter is increased to improve equalization performance, then the equalization accuracy is improved, but the circuit complexity and cost increase
Solution Approach 1:
The patent replaces the conventional mechanical approach of increasing tap quantity to improve equalization accuracy with a digital signal processing approach. By calculating the weighted center of existing tap coefficients and shifting them to optimize convergence, the system achieves improved equalization performance without adding more hardware taps, thus reducing circuit complexity while maintaining accuracy.
2Adaptability or versatility
If tap coefficients are updated rapidly to follow propagation characteristic changes, then the adaptability is improved, but the calculation complexity and processing time increase
Solution Approach 1:
The patent implements a feedback mechanism where the weighted center of tap coefficients is continuously calculated and used to determine shifting operations. This feedback loop enables the system to adapt to propagation characteristic changes by monitoring the convergence state and adjusting tap coefficients accordingly, achieving high follow-up rate without excessive calculation complexity through efficient use of existing coefficient data.
Solution Approach 2:
The patent performs preliminary calculation of the weighted center of tap coefficients before actual coefficient updates are needed. By pre-calculating the weighted center position and determining the optimal shifting amount in advance, the system reduces real-time calculation complexity while maintaining rapid adaptability to changing propagation characteristics.
3Stability of the object's composition
If tap coefficients are shifted frequently to maintain convergence during communications, then the equalization stability is improved, but the processing overhead increases
Solution Approach 1:
The patent implements periodic shifting of tap coefficients based on the calculated weighted center rather than continuous adjustment. By performing shifting operations at optimal intervals during communications based on convergence monitoring, the system maintains equalization stability while minimizing processing overhead and avoiding unnecessary frequent adjustments.
Data Source
AI summary
An adaptive equalizer includes a finite impulse response filter with a predetermined number of taps; and a tap coefficient adaptive controller having a register to hold tap coefficients for the filter, a weighted center calculator to calculate a weighted center of the tap coefficients, and a tap coefficient shifter to shift the tap coefficients based on a calculation result of the weighted center. During an initial training period, the tap coefficient shifter shifts the tap coefficients on a symbol data basis such that a difference between the calculated weighted center of the tap coefficients and a tap center defined by the number of taps is minimized.