Multi-core optical fiber crosstalk reduction
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Solution Overview
Problem
Conventional mode division multiplexing transmission using multi-mode optical fibers requires complex structures and precise adjustments for coupling signal light beams, and suffers from high optical loss due to asymmetrical field distribution and interference among signal light beams.
Innovation Solution
A multi-core optical fiber with a cladding portion having a lower refractive index than the core portions, where the separation distance between adjacent cores is set to achieve crosstalk of -15 dB or greater at 1550 nm, enabling mode division multiplexing transmission using supermodes without the need for complex coupling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional mode division multiplexing transmission uses multi-mode optical fibers with higher-order propagation modes, then transmission capacity per optical fiber can be increased, but complex structures and precise adjustments are required for coupling signal light beams
Solution Approach 1:
The invention divides a single optical fiber into multiple independent core portions (e.g., seven cores arranged in a hexagonal pattern around a central core). Each core can independently transmit signal light beams without requiring complex coupling systems. This segmentation approach achieves space division multiplexing while maintaining simple coupling structures, as each core acts as an independent transmission channel.
Solution Approach 2:
The invention transitions from mode division multiplexing (utilizing different propagation modes within a single core) to core division multiplexing (utilizing multiple spatially separated cores). By adding the spatial dimension of multiple cores, the system achieves higher transmission capacity without the complexity of mode coupling control, as each core provides an independent transmission path.
2Quantity of substance
If conventional mode division multiplexing transmission uses multi-mode optical fibers, then transmission capacity can be increased, but precise adjustments are required for input position at fiber facet due to asymmetrical field distribution
Solution Approach 1:
By segmenting the optical fiber into multiple independent cores, each core transmits signal light beams independently without requiring precise alignment for mode coupling. The segmentation eliminates the need for asymmetrical field distribution management, as each core operates as a separate transmission channel with its own symmetric field pattern.
Solution Approach 2:
Instead of managing asymmetrical field distribution within a single multi-mode fiber, the invention inverts the approach by using multiple single-mode-like cores. This inversion transforms the problem from controlling field distribution asymmetry to managing independent core transmissions, thereby eliminating the need for precise input position adjustments.
3Quantity of substance
If conventional mode division multiplexing transmission uses multi-mode optical fibers, then transmission capacity can be increased, but interference among signal light beams causes distortion and deterioration in signal quality
Solution Approach 1:
The invention segments the transmission medium into multiple independent cores, where each core transmits signal light beams independently. This segmentation prevents interference among signal light beams by providing physical isolation between transmission paths, thereby maintaining signal quality while achieving high transmission capacity through space division multiplexing.
Solution Approach 2:
The cladding portions surrounding each core act as intermediaries that optically isolate adjacent cores. By introducing this intermediary structure with appropriate refractive index differences, the invention prevents harmful optical interference between cores while allowing controlled crosstalk management, thus preserving signal quality in high-capacity multi-core transmission.
4Area of stationary object
If separation distance between adjacent core portions is reduced to increase core density, then space utilization improves, but crosstalk of light between adjacent cores increases
Solution Approach 1:
The invention optimizes the separation distance between adjacent cores as a critical parameter to achieve the desired balance between core density and crosstalk. By carefully selecting the separation distance (e.g., specific micrometer ranges), the system maximizes space utilization while maintaining acceptable signal isolation. This parameter optimization allows high core density without excessive crosstalk, enabling efficient space division multiplexing.
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 configuration allows for stable propagation of signal light beams in supermodes, reducing optical loss and eliminating the need for precise adjustments, thereby enhancing signal quality and transmission efficiency.
Implementation Method 1
a cladding portion (32) that is positioned around each of the plurality of core portions (311 to 317) and has a refractive index lower than that of each of the plurality of core portions (311 to 317)
Implementation Method 2
a separation distance between adjacent ones of the plurality of core portions (311 to 317) being set so that crosstalk of light between the adjacent core portions over an entire length thereof becomes −15 dB or greater
Data Source
AI summary
A multi-core optical fiber has: a plurality of core portions; a cladding portion that is positioned around each of the plurality of core portions and has a refractive index lower than that of each of the plurality of core portions; and a separation distance between adjacent ones of the plurality of core portions being set so that crosstalk of light between the adjacent core portions over an entire length thereof becomes −15 dB or greater at a wavelength of 1550 nm and a cable cut-off wavelength becomes 1530 nm or less.