8×8 MIMO Equalizer for Coherent Receiver I/Q Skew Compensation
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Solution Overview
Problem
Conventional optical communication systems face performance limitations and high complexity due to transmitter I/Q skew and quadrature error in subcarrier multiplexing schemes, leading to signal degradation and increased channel noise.
Innovation Solution
A reduced complexity 8×8 adaptive equalizer is developed to compensate for transmitter I/Q imbalance and skew, featuring a multi-subcarrier coherent optical receiver device with a digital signal processor that includes a chromatic dispersion equalizer, carrier recovery module, cycle slip correction module, and a reduced complexity 8×8 MIMO equalizer, where each output is coupled to three inputs as filters, significantly reducing complexity while maintaining receiver performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional 8×8 adaptive equalizer is used to compensate transmitter I/Q skew and quadrature error, then receiver performance is maintained, but device complexity and power consumption increase significantly
Solution Approach 1:
The patent segments the equalizer architecture by separating chromatic dispersion compensation and polarization-mode dispersion compensation into dedicated modules, with a simplified 8×8 MIMO equalizer handling only the remaining I/Q skew and quadrature error compensation. This modular segmentation reduces the computational burden on each individual module while maintaining overall receiver performance.
Solution Approach 2:
The patent implements dynamic adaptation in the equalizer coefficients through iterative optimization algorithms that continuously adjust the filter parameters based on received signal characteristics. This dynamic adjustment allows the equalizer to maintain optimal performance under varying channel conditions without requiring excessive computational resources.
2Manufacturing precision
If phase and gain imbalance of the modulator is completely compensated at the receiver, then signal quality improves, but channel noise is amplified
Solution Approach 1:
The patent applies partial compensation by designing the equalizer to correct the most critical components of I/Q skew and quadrature error while deliberately leaving some residual imbalance uncompensated. This partial action approach prevents excessive noise amplification that would result from attempting complete compensation, achieving an optimal trade-off between signal quality and noise levels.
3Reliability
If transmitter I/Q skew and quadrature error are compensated using conventional methods, then signal degradation is reduced, but power consumption increases
Solution Approach 1:
The patent extracts and removes the computationally intensive chromatic dispersion compensation and polarization-mode dispersion compensation functions from the main equalizer processing chain, handling them in separate dedicated modules. This extraction leaves the 8×8 MIMO equalizer to focus only on I/Q skew and quadrature error compensation, significantly reducing its power consumption while maintaining effective signal degradation compensation.
Data Source
AI summary
A method and structure for compensation techniques in coherent optical receivers. The present invention provides a coherent optical receiver with an improved 8×8 adaptive MIMO (Multiple Input, Multiple Output) equalizer configured within a digital signal processor (DSP) to compensate the effects of transmitter I/Q skew in subcarrier multiplexing (SCM) schemes. The 8×8 MIMO equalizer can be configured such that each of the 8 outputs is electrically coupled to 3 of 8 inputs, wherein each of the input-output couplings is configured as a filter. The method includes compensating for impairments to the digital conversion of an optical input signal via the 8×8 MIMO equalizer following other signal processing steps, such as chromatic dispersion (CD)/polarization-mode dispersion (PMD) compensation, carrier recovery, timing synchronization, and cycle slip correction.