Unified MIMO Equalization for Digital Coherent Optical Transmission
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Solution Overview
Problem
Existing adaptive equalization circuits in digital coherent optical transmission systems are not compatible with 2×2 Multiple Input Multiple Output (MIMO) circuits, leading to increased computational complexity and inability to support multicarrier signals.
Innovation Solution
A signal processing method that converts real and imaginary components of received signals into frequency domain signals, performs sub-carrier selection, and applies complex transfer functions for equalization, while also compensating for frequency offset and data bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adaptive equalization circuits are used, then device imperfections can be compensated, but the total number of taps increases and computational complexity increases exponentially
Solution Approach 1:
The patent combines transmitter imperfection compensation and receiver imperfection compensation into a single unified equalization process. By merging these previously separate compensation functions into one integrated approach using 2×2 MIMO adaptive equalization, the system achieves comprehensive device imperfection compensation without requiring separate processing stages, thereby reducing overall computational complexity
Solution Approach 2:
The patent creates a universal equalization circuit that can handle both transmitter and receiver imperfections simultaneously, as well as support both single-carrier and multicarrier signals. This multi-functional approach eliminates the need for separate compensation circuits for different scenarios, reducing the total number of taps and computational requirements while maintaining comprehensive compensation capability
2Reliability
If existing adaptive equalization circuits are used, then waveform distortion can be compensated, but they cannot support multicarrier signals
Solution Approach 1:
The patent designs a universal equalization circuit that is capable of handling multiple signal types including both single-carrier and multicarrier signals. The 2×2 MIMO adaptive equalization structure provides sufficient degrees of freedom to compensate for waveform distortion in multicarrier signals while maintaining compatibility with single-carrier operations, thereby achieving versatility without sacrificing compensation performance
Solution Approach 2:
The patent applies frequency-domain processing by dividing the signal into sub-carriers, allowing the equalization to be performed independently on each sub-carrier. This segmentation approach enables the system to handle multicarrier signals effectively while maintaining the ability to compensate for waveform distortion, as each sub-carrier can be processed with appropriate equalization filters
3Reliability
If the number of taps is increased to improve compensation, then device imperfections can be compensated better, but the amount of calculation increases exponentially
Solution Approach 1:
By merging transmitter and receiver compensation into a single equalization process with shared taps, the system achieves better compensation performance without requiring separate sets of filters. This merging reduces the total number of taps needed compared to having independent compensation paths, thereby reducing the exponential increase in computational complexity while maintaining comprehensive compensation capability
Data Source
AI summary
A signal processing method of converting a real number component and an imaginary number component of each polarization of a sub-carrier-multiplexed and polarization-multiplexed received signal into a frequency domain signal; selecting a frequency domain signal corresponding to a sub-carrier; receiving, as input signals, a real number component and an imaginary number component of each polarization of each sub-carrier and frequency inversion and phase conjugation, performing a first equalization process of multiplying, for each sub-carrier and polarization, the real number component and the imaginary number component of each polarization included in the input signal by a complex transfer function and then adding them and performing inverse conversion from a frequency domain signal into a time domain signal and a second equalization process of performing a signal of a real number component obtained by subjecting the real number component of each polarization included in the input signal to frequency inversion and taking complex conjugation and a signal of an imaginary number component obtained by subjecting the imaginary number component to frequency inversion and taking complex conjugation by a complex transfer function and then adding them, and performing inverse conversion from a frequency domain signal into a time domain signal, and adding or subtracting the transmission data bias correction signal to or from the signal obtained by adding the first addition signal and the second addition signal.