Coherent Optical Receiver Equalization Using Reduced-Complexity CFBLMS
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical communication systems face performance limitations and high power consumption due to misalignment of data channels caused by delay, which degrades data recovery in receivers, and existing devices are inadequate for modern high-bandwidth applications.
Innovation Solution
A coherent optical receiver device employing a reduced complexity constrained frequency-domain block least means square (CFBLMS) algorithm, which uses frequency-domain filtering to compensate for chromatic dispersion and polarization mode dispersion, reducing implementation complexity and achieving better performance than unconstrained methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adaptive equalization algorithms are used to compensate for chromatic dispersion and polarization mode dispersion, then equalization performance is improved, but implementation complexity and power consumption increase
Solution Approach 1:
The patent segments the adaptive equalization process into distinct functional modules: a chromatic dispersion equalizer module that compensates for CD, and a polarization mode dispersion equalizer module that compensates for PMD. This segmentation allows each module to be optimized independently, reducing overall implementation complexity while maintaining equalization performance.
Solution Approach 2:
The patent introduces an intermediary constrained frequency-domain block least means square (CFBLMS) module that mediates between the CD equalizer and PMD equalizer. This intermediary module processes the equalized signal through frequency-domain filtering, simplifying the computational requirements and reducing implementation complexity compared to conventional time-domain algorithms.
2Reliability
If conventional adaptive equalization algorithms are used to compensate for chromatic dispersion and polarization mode dispersion, then equalization performance is improved, but power consumption increases
Solution Approach 1:
The patent replaces computationally intensive time-domain adaptive filtering operations with frequency-domain filtering operations. By transforming the equalization process to the frequency domain, the system reduces the number of multiplications and additions required, thereby lowering power consumption while maintaining equalization performance.
3Speed
If standard CFBLMS algorithm is used for frequency-domain equalization, then convergence speed is improved, but implementation complexity increases
Solution Approach 1:
The patent modifies the standard CFBLMS algorithm by changing the domain of operation from time-domain to frequency-domain. This parameter change enables faster convergence through frequency-domain parallel processing while the modular architecture and intermediary processing stages reduce the overall implementation complexity.
Data Source
AI summary
A method and structure for equalization in coherent optical receivers. Block-based LMS (BLMS) algorithm is one of the many efficient adaptive equalization algorithms used to (i) increase convergence speed and (ii) reduce implementation complexity. Since the computation of the equalizer output and the gradient of the error are obtained using a linear convolution, BLMS can be efficiently implemented in the frequency domain with the constrained frequency-domain BLMS (FBLMS) adaptive algorithm. The present invention introduces a novel reduced complexity constrained FBLMS algorithm. This new approach replaces the two discrete Fourier transform (DFT) stages required to evaluate the DFT of the gradient error, by a simple frequency domain filtering. Implementation complexity can be drastically reduced in comparison to the standard constrained FBLMS. Furthermore, the new approach achieves better performance than that obtained with the unconstrained FBLMS in ultra-high speed coherent optical receivers.