Polarization Monitoring via FFT Tap Coefficient Shift
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Solution Overview
Problem
Current methods for monitoring the change of state of polarization in optical communication systems are affected by transmitter imperfections such as direct current and phase imbalance, leading to errors in the measured change of state of polarization.
Innovation Solution
Performing an FFT operation on the equalization filter tap coefficients shifts the sum of the tap coefficients from zero frequency to non-zero frequency, thereby avoiding the impact of transmitter imperfections and improving the accuracy of polarization state monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sum of equalization filter tap coefficients is calculated at zero frequency to monitor state of polarization change, then the measurement process is simple, but transmitter imperfections such as direct current and phase imbalance cause errors in the measured change of state of polarization
Solution Approach 1:
The patent changes the frequency parameter from zero frequency to non-zero frequency for the sum calculation. By performing FFT operation and calculating the sum at a non-zero frequency point instead of DC component, the method eliminates the influence of transmitter imperfections while maintaining measurement accuracy.
Solution Approach 2:
The patent extracts the useful signal component at non-zero frequency from the FFT spectrum, separating it from the DC component that contains transmitter imperfections. This extraction allows the system to ignore harmful DC components while utilizing the clean non-zero frequency components for accurate polarization monitoring.
2Measurement precision
If FFT operation is performed on equalization filter tap coefficients to shift sum from zero frequency to non-zero frequency, then accuracy of polarization monitoring is improved, but computational complexity increases
Solution Approach 1:
The patent performs partial FFT operation only on the equalization filter tap coefficients that are necessary for polarization monitoring, rather than processing the entire signal spectrum. This selective processing reduces computational energy consumption while still achieving the goal of eliminating DC component interference.
Data Source
AI summary
A method and apparatus for monitoring the change of state of polarization and a receiver. The method for monitoring the change of state of polarization includes: extracting a matrix of equalization filter tap coefficients of a receiver; performing an FFT operation of N taps on each path of equalization filter tap coefficients of the matrix to obtain a converted matrix, a sum of each path of equalization filter tap coefficients of the converted matrix being a value of non-zero frequency; and estimating an amount of change of state of polarization by using at least one path of equalization filter tap coefficients of the converted matrix. Thus, as the sum of the tap coefficients is shifted in the frequency domain from the zero frequency to a higher frequency (non-zero frequency), an effect of imperfection of the transmitter on a monitoring result of the change of state of polarization may be avoided.