Optical Signal Receiver Frequency Domain Filtering
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Solution Overview
Problem
Current optical communication systems face challenges in efficiently equalizing chromatic dispersion and polarization mode dispersion due to the complexity of combining static and dynamic filters, with existing methods often requiring impractical updates of filter coefficients and increasing tap noise.
Innovation Solution
The proposed method performs filtering operations in the frequency domain while updating coefficients in the time domain, reducing the number of samples per symbol and using a combination of static and dynamic filters to efficiently equalize optical signals, with the option to update only a subset of coefficients to minimize tap noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filtering operations are performed in the frequency domain with updates of all coefficients, then equalization performance is improved, but tap noise increases and complexity increases
Solution Approach 1:
The patent segments the filter coefficients into two groups: pilot symbols (first set) and data symbols (second set). Only the pilot symbol coefficients are updated during filtering operations, while the data symbol coefficients remain fixed. This segmentation allows the system to maintain equalization performance through selective updating while reducing tap noise and computational complexity by avoiding unnecessary updates of all coefficients.
2Productivity
If filtering operations are performed in the frequency domain, then equalization efficiency is improved, but device complexity increases
Solution Approach 1:
The patent divides the filtering process into two distinct phases: a training phase where frequency-domain filtering is performed to establish optimal coefficients using pilot symbols, and a data processing phase where the established coefficients are applied without frequent updates. This segmentation maintains high equalization efficiency while reducing the computational complexity and processing overhead of continuous frequency-domain operations.
Solution Approach 2:
The patent performs preliminary frequency-domain filtering operations during the training phase to determine optimal filter coefficients before actual data transmission. By pre-establishing the filtering parameters using known pilot symbols, the system avoids the need for complex real-time frequency-domain updates during data processing, thereby reducing device complexity while maintaining equalization efficiency.
3Device complexity
If the number of samples per symbol is reduced, then filter complexity is reduced, but performance may be adversely affected
Solution Approach 1:
The patent changes the parameter of samples per symbol from the conventional two samples per symbol to a reduced number (one or more but less than two samples per symbol). This parameter change reduces filter complexity and processing requirements while the use of frequency-domain filtering and selective coefficient updating compensates for any potential performance loss, maintaining reliable decoding.
4Measurement precision
If static and dynamic filters are combined for equalization, then equalization accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of static chromatic dispersion compensation filters and dynamic polarization mode dispersion equalization filters into a unified frequency-domain filtering approach. By combining these separate equalization functions into a single filtering operation with selectively updated coefficients, the system achieves high equalization accuracy for both chromatic dispersion and polarization mode dispersion while reducing the overall device complexity and avoiding the challenges of coordinating multiple separate filters.
Data Source
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AI summary
A method decodes an optical signal transmitted over an optical channel from a transmitter to a receiver. The receiver receives the transmitted optical signal to produce a digital signal which is filtered in the frequency domain for compensating static effects and/or dynamic effects. The filtering is performed in the frequency domain, while the frequency coefficients of the filter are updated in the time domain by updating at least some of time coefficients of the filter and transforming the time coefficients into the frequency domain.