Mode-Division Multiplexing Fiber System Using Segmented MIMO Equalization
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Solution Overview
Problem
The complexity of multiple-input multiple-output algorithms in mode-division multiplexing fiber-optic communication systems increases with the number of mode channels, limiting system expansion and spectral efficiency, especially in systems using orbital angular momentum and few-mode optical fibers.
Innovation Solution
A construction method for a mode-division multiplexing fiber-optic communication system using graded-index ring-core optical fibers, where optical signals are multiplexed and transmitted, then de-multiplexed and converted into Gaussian modes for single-mode fiber transmission, utilizing 2×2 or 4×4 multiple-input multiple-output equalization algorithms based on digital signal processing for recovery processing, depending on the mode group order.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of multiplexing mode groups is increased to expand system capacity, then the spectral efficiency is improved, but the complexity of the multiple-input multiple-output equalization algorithm increases
Solution Approach 1:
The patent segments the mode groups into different categories (e.g., LP01 fundamental mode group, LP11 first higher-order mode group, etc.) and applies different equalization algorithm sizes to each segment. Specifically, 2×2 MIMO equalization is used for mode groups with 2 modes, 4×4 MIMO equalization for mode groups with 4 modes, and larger equalization for mode groups with more modes. This segmentation allows the system to expand capacity by adding more mode groups while keeping the algorithm complexity manageable through selective application of appropriate equalization sizes.
2Reliability
If a 4×4 multiple-input multiple-output algorithm is used to equalize crosstalk in higher order mode groups, then the equalization capability is improved, but the algorithm complexity becomes difficult to manage when mode groups contain more than four degenerate modes
Solution Approach 1:
The patent dynamically changes the parameter of equalization algorithm size based on the number of degenerate modes in each mode group. Instead of uniformly applying 4×4 MIMO equalization to all mode groups, the system adapts the equalization matrix size to match the actual number of modes: 2×2 for 2-mode groups, 4×4 for 4-mode groups, and appropriately larger matrices for groups with more modes. This parameter adaptation maintains equalization capability while optimizing computational complexity.
3Productivity
If mode-division multiplexing is implemented to improve spectral efficiency, then the transmission capacity is increased, but the system becomes more susceptible to crosstalk among modes
Solution Approach 1:
The patent implements digital signal processing with multiple-input multiple-output equalization that continuously monitors and compensates for crosstalk effects. The system uses feedback mechanisms where the received signals from multiple mode groups are processed through MIMO equalization algorithms that calculate and subtract inter-mode interference, thereby recovering the original transmitted signals with reduced crosstalk impact.
Data Source
AI summary
The present invention relates to a construction method of a mode-division multiplexing fiber-optic communication system, which includes following contents: converting multiple-input optical signals into optical propagation modes supported by a graded-index ring-core optical fiber at a transmitting end, after being multiplexed by a mode multiplexer, injecting the optical signals into the graded-index ring-core optical fiber for transmission; using a mode de-multiplexer to separate optical signals of different mode groups at a receiving end firstly; and for the separation of internal modes of the same mode group, adopting a multi-channel reception and a digital signal processing method based on a multiple-input multiple-output equalization for processing: for the separation of modes in a base mode group and a high-order mode group, using a digital signal processing algorithm including a 2×2 multiple-input multiple-output equalization and a digital signal processing algorithm including a 4×4 multiple-input multiple-output equalization for recovery processing, respectively. The method according to the present invention only needs to add an optical receiver and a digital signal processing module based on the 4×4 multiple-input multiple-output equalization repeatedly while adding the mode group to expand communication capacity. Compared with the prior art, the present invention has the characteristics of low complexity, high scalability and easy upgrading.