Mode Selection for MIMO Optical Fiber Transmission
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Solution Overview
Problem
MIMO optical transmissions over multimode or multicore fibers are complex and costly due to high processing complexity and require selecting modes/cores for efficient transmission, which is challenging especially for a high number of modes/cores.
Innovation Solution
A method involving measuring the transfer matrix of the transmission channel, transforming it into a block diagonal matrix, determining gain and/or capacity for mode or core subsets, and selecting the subset with the highest gain or capacity for MIMO transmission, potentially using space-time coding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MIMO techniques are implemented to separate transmission over different modes or cores, then transmission capacity increases, but processing complexity increases at best in terms of O(M3)
Solution Approach 1:
The patent extracts and eliminates the need for complex MIMO processing by using space-time coding techniques that achieve diversity gain without requiring sophisticated signal separation algorithms. This reduces processing complexity from O(M3) to much lower levels while maintaining transmission capacity.
Solution Approach 2:
The patent changes the approach from complex spatial processing to simpler time-domain coding, transforming the problem from one requiring high computational power to one solvable with basic processing while achieving the same or better transmission performance.
2Reliability
If MIMO techniques are implemented with space-time coding, then bit error ratio decreases significantly, but the system requires M RF subsystems in parallel increasing transceiver cost
Solution Approach 1:
The patent extracts the essential diversity function from complex MIMO RF subsystems and implements it through simpler space-time coding in the baseband, eliminating the need for multiple expensive parallel RF chains while maintaining low bit error ratios.
Solution Approach 2:
The patent uses coding techniques that create redundant information copies across time and space, achieving error protection without requiring multiple physical RF subsystems, thereby reducing transceiver cost while maintaining reliability.
3Productivity
If all modes or cores are used for transmission, then transmission capacity is maximized, but inter-mode coupling and inter-core crosstalk limit the range
Solution Approach 1:
The patent converts the harmful effects of inter-mode coupling and inter-core crosstalk into useful diversity effects through space-time coding, where the coupling that was previously degrading performance now provides additional signal paths that improve reliability and extend transmission range.
Data Source
AI summary
The invention relates to a mode selection method for a system for MIMO transmission on an optical fiber of multimode type. It comprises a step of measuring the transfer matrix of the transmission channel made up of a set of modes of the optical fiber (110), a step of transforming (120) the transfer matrix into a block diagonal matrix, each block being associated with a mode subset, a step of determining (130) the gain and/or the transmission capacity for each of the mode subsets, and a selection (140) of the mode subset corresponding to the highest gain and/or capacity, the MIMO transmission system then using only the modes of the subset thus selected to transmit on the optical fiber.The invention relates also to a core selection method for a system for MIMO transmission on optical fiber of multicore type.