Multi-core fiber annular core arrangement for crosstalk suppression
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Solution Overview
Problem
Trench type multi-core fibers face challenges in reducing core pitch due to long cutoff wavelength, limiting the number of cores that can be disposed within a given clad diameter, and experiencing varying crosstalk levels between cores, which degrades communication quality.
Innovation Solution
The multi-core fiber design arranges cores in an annular configuration without hexagonal close packing, allowing for a smaller core pitch and increased core count, with a trench type refractive index profile to suppress crosstalk, ensuring uniform crosstalk levels and maintaining communication quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cores are arranged in hexagonal close packing with a specific core surrounded by multiple cores, then the cutoff wavelength becomes long and communication quality deteriorates, but the core pitch cannot be reduced
Solution Approach 1:
The patent applies asymmetry by positioning a specific core (the center core) at a different radial distance from the clad outer circumference compared to other cores. The center core has a larger radial distance, while outer cores have smaller radial distances. This asymmetric arrangement balances the mode field diameter and confinement characteristics, preventing excessively long cutoff wavelengths while allowing reduced core pitch.
Solution Approach 2:
The patent applies local quality by giving different radial distances from the clad outer circumference to different cores based on their positions. The center core receives a larger radial distance to maintain appropriate mode field diameter and cutoff wavelength, while outer cores can have smaller radial distances. This localized differentiation optimizes communication quality for each core position while enabling overall compact design.
2Quantity of substance
If the core pitch is reduced to increase the number of cores in the clad, then more cores can be disposed, but crosstalk between cores increases and communication quality degrades
Solution Approach 1:
The patent applies the intermediary principle by introducing a clad layer with refractive index positioned between the core refractive index and the surrounding medium refractive index. This intermediate refractive index creates an optical barrier that confines light within cores, suppressing crosstalk even when core pitch is reduced to increase the number of cores that can be disposed in the clad.
3Object-affected harmful factors
If a trench type structure is used to confine light and reduce crosstalk, then crosstalk is suppressed, but the cutoff wavelength becomes long in cores surrounded by multiple cores
Solution Approach 1:
The patent applies local quality by differentiating the radial distances from the clad outer circumference for different core positions. The center core has a larger radial distance to maintain appropriate cutoff wavelength and mode field diameter, while outer cores have smaller radial distances. This localized optimization allows the trench type structure to effectively suppress crosstalk without causing excessively long cutoff wavelengths in specific cores.
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 design enables a larger number of cores to be disposed within a clad while maintaining low crosstalk, ensuring uniform communication quality and reducing optical attenuation, even when connected in bundles.
Implementation Method 1
the refractive index of the first clad is higher than the refractive index of the core, and the refractive index of the second clad is lower than the refractive indices of the first clad and the clad... light propagating through the core is more properly confined in the cores
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
There is provided a multi-core fiber that can dispose a large number of cores according to the outer diameter of a clad while suppressing the crosstalk between cores adjacent to each other. A multi-core fiber (1) includes six or more of core elements (10) having a core (11) a first clad (12) surrounding the outer circumferential surface of the core (11) and a second clad (13) surrounding the outer circumferential surface of the first clad (12), and includes a clad (20) surrounding the core elements (10). All of expressions are satisfied: n1>n2>n3 n1>n4 n3<n4 wherein the refractive index of the core (11) is n1, the refractive index of the first clad (12) is n2, the refractive index of the second clad (13) is n3, and the refractive index of the clad (20) is n4. The core elements (10) are disposed so that the inter-center pitch between the cores (11) adjacent to each other is disposed at regular spacings and the centers of the cores (11) are annularly disposed.