Few-Mode Fiber Spatial Mode Multiplexing for Capacity Expansion
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Solution Overview
Problem
Current optical communication systems using single-mode fibers are limited to about 100 Tbit/s transmission capacity, and space division multiplexing technologies like multicore and few-mode fibers require replacement of existing networks to overcome this limit.
Innovation Solution
A method and device for injecting multiple optical beams into an optical fiber with a guiding structure composed of a core, cladding, and sheath with different refractive indices, allowing for increased transmission capacity by modulating beams with data and using spatial mode conversion to combine single-mode, few-mode, and multimode fibers into a single output fiber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If space division multiplexing is implemented using multicore fibers or few-mode fibers, then transmission capacity exceeds 100 Tbit/s, but existing single-mode fiber networks must be replaced
Solution Approach 1:
The patent combines multiple single-mode fiber transmission systems into a single few-mode fiber transmission system. By using mode division multiplexing to transmit multiple spatial modes (LP01, LP11, LP21, etc.) simultaneously in the few-mode fiber, it merges the functionality of multiple SMF channels into one fiber, achieving higher capacity without replacing the entire network infrastructure.
Solution Approach 2:
The few-mode fiber is designed to support multiple transmission modes (both fundamental LP01 mode and higher-order modes like LP11, LP21) within the same fiber structure. This multi-functionality allows the single fiber to replace multiple single-mode fibers while maintaining compatibility with existing single-mode fiber connectors and splices at the input and output ends.
2Productivity
If multiple propagation modes are transmitted in parallel in the same fiber, then transmission capacity increases, but the guiding structure must be changed from single-mode to multi-core or few-mode fiber
Solution Approach 1:
The patent transitions from transmitting multiple modes in the transverse spatial dimension (as in multicore fibers) to utilizing the longitudinal propagation dimension. By exciting higher-order modes in a few-mode fiber and controlling their propagation constants, it creates distinct transmission channels along the same spatial path, effectively adding a dimensional layer to mode multiplexing.
Solution Approach 2:
The patent changes the refractive index parameters of the few-mode fiber to support specific higher-order modes. By carefully designing the core-cladding refractive index difference and fiber dimensions, it enables the propagation of LP11, LP21, and other higher-order modes while maintaining single-mode operation at the input and output facets, thus controlling device complexity through parameter optimization.
3Adaptability or versatility
If single-mode fibers are used, then network compatibility is maintained, but transmission capacity is limited to about 100 Tbit/s
Solution Approach 1:
The few-mode fiber acts as an intermediary between existing single-mode fiber networks and high-capacity transmission requirements. The system uses single-mode fibers for input and output connections to maintain network compatibility, while the few-mode fiber in the middle section provides the capability for high-capacity mode-division multiplexing, thus bridging the gap between legacy infrastructure and advanced transmission needs.
Solution Approach 2:
The transmission system is segmented into three parts: single-mode input fiber, few-mode transmission fiber, and single-mode output fiber. This segmentation allows each section to perform its optimal function - the single-mode sections maintain compatibility with existing networks, while the few-mode section provides enhanced capacity through multiple spatial modes, resolving the contradiction between compatibility and capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables higher injection of optical beams into existing fibers, enhancing transmission capacity without the need to replace existing networks, allowing for increased data transmission through existing optical communication systems.
Implementation Method 1
an output optical fiber the guiding structure of which is composed of a core with a first refractive index, of a cladding with a second refractive index, and of a sheath with a third refractive index
Data Source
AI summary
A device for inserting a plurality of optical beams into a single-mode optical fibre, a guiding structure of which is composed of a core with a first refractive index, a cladding with a second refractive index, and a coating with a third refractive index. The device includes an optical mixer configured to insert, into the single-mode optical fibre, the plurality of optical beams, at least one of which has a distribution of its radial and angular electromagnetic amplitude with a maximum amplitude peak in the cladding.