Multicore Optical Fiber Cladding Barrier for Crosstalk and Loss
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Solution Overview
Problem
Existing multicore optical fibers face challenges in simultaneously reducing inter-core crosstalk (XT) and transmission loss, as current methods either increase XT with closer core spacing or reduce core capacity with larger spacing.
Innovation Solution
Incorporating a low refractive index barrier with an alkali metal element in the cladding, setting core intervals to minimize power coupling coefficients, and optimizing refractive index differences to suppress XT and transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the inter-core distance is shortened to increase core capacity, then the number of cores that can be accommodated increases, but inter-core crosstalk increases
Solution Approach 1:
The cladding is segmented into multiple functional regions: a first cladding region surrounding all cores, and a second cladding region with a low refractive index barrier positioned between specific cores. This segmentation allows the low refractive index barrier to act as an optical isolation structure that reduces inter-core crosstalk while maintaining close core spacing for high core capacity.
Solution Approach 2:
The low refractive index barrier is selectively positioned in the second cladding region between specific cores that require optical isolation, rather than uniformly across all cladding. This local quality approach reduces crosstalk only where needed between adjacent cores while maintaining efficient light transmission in other regions.
2Object-generated harmful factors
If the inter-core distance is increased to reduce inter-core crosstalk, then inter-core crosstalk decreases, but the number of cores that can be accommodated decreases
Solution Approach 1:
The cladding is divided into a first cladding region providing general structural support and a second cladding region containing the low refractive index barrier for optical isolation. This segmentation enables close core spacing while maintaining low crosstalk through the barrier structure.
Solution Approach 2:
The low refractive index barrier acts as an intermediary optical isolation structure positioned between specific cores in the second cladding region. It mediates the optical interaction between adjacent cores, preventing crosstalk while allowing the cores to maintain close spacing for high capacity.
3Loss of energy
If an alkali metal element is doped to the core and cladding to reduce transmission loss, then transmission loss decreases, but refractive index control becomes challenging
Solution Approach 1:
The alkali metal element is doped at different concentrations in different regions: a first concentration in the first cladding region and a second concentration in the second cladding region. This local quality approach allows independent control of refractive index in each region, enabling precise refractive index management while maintaining low transmission loss through alkali metal doping.
Solution Approach 2:
The concentration of the alkali metal element is varied as a parameter to control refractive index: a first concentration in the first cladding region and a second concentration in the second cladding region. This parameter change strategy enables precise refractive index control in each region while maintaining the transmission loss reduction benefits of alkali metal doping.
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
The solution effectively reduces inter-core XT and transmission loss by stabilizing refractive index differences and viscosity during fiber drawing, allowing for efficient single-mode transmission with multiple cores.
Implementation Method 1
The cladding includes a low refractive index barrier. The low refractive index barrier includes an alkali metal element. A relative refractive index of the low refractive index barrier is lower than an average value of relative refractive indices of the cladding overall.
Implementation Method 2
The solution effectively reduces inter-core XT and transmission loss by stabilizing refractive index differences and viscosity during fiber drawing
Data Source
AI summary
An MCF includes a plurality of cores each extending in a direction along a central axis and a cladding covering each of the plurality of cores. The cladding includes a low refractive index barrier. The low refractive index barrier includes an alkali metal element. A relative refractive index of the low refractive index barrier is lower than an average value of a relative refractive indices of the cladding overall. The core interval is set such that a total sum of the power coupling coefficients between a specific core among the plurality of cores and each of all remaining cores is 2.3×10−4/km or less.