Uncoupled Multicore Fiber With Trench Regions
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Solution Overview
Problem
Current multicore optical fiber designs struggle to achieve high capacity and low attenuation while maintaining acceptable crosstalk levels, especially when incorporating multiple uncoupled cores within a common cladding.
Innovation Solution
The development of an uncoupled multicore optical fiber with a common cladding and multiple core portions, each featuring a core region with an alkali dopant and a trench region, optimized for low attenuation, large effective area, and reduced crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple uncoupled cores are incorporated within a common cladding to increase transmission capacity, then the bandwidth and transmission capacity are improved, but the crosstalk between adjacent cores increases and manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating distinct refractive index regions around each core. Each core is surrounded by a trench region with lower refractive index than the common cladding, creating localized optical confinement. This ensures that optical fields remain confined to individual cores, reducing crosstalk between adjacent cores while maintaining high transmission capacity through multiple cores.
Solution Approach 2:
The trench region acts as an intermediary structure between the core and common cladding. This intermediate layer with its specific refractive index (lower than both core and common cladding) serves as an optical barrier that prevents coupling between adjacent cores, thereby reducing crosstalk while allowing multiple cores to coexist in the common cladding.
2Loss of energy
If the effective area is increased to reduce attenuation and improve transmission quality, then the attenuation is reduced, but the fiber diameter and overall size increase
Solution Approach 1:
The patent employs a nested structure where multiple core portions are embedded within a single common cladding. Each core is surrounded by a trench region, creating a nested configuration (core within trench within common cladding). This nesting allows multiple cores with large effective areas to be packed into a compact fiber structure, achieving low attenuation without excessive fiber diameter increase.
3Strength
If alkali dopants are used in core regions to increase refractive index and improve optical confinement, then the refractive index contrast is improved, but the attenuation may increase due to absorption
Solution Approach 1:
The patent applies local quality by concentrating the alkali dopant specifically in the core region while keeping the common cladding and trench region free of alkali dopants. This localized doping creates the necessary refractive index contrast for optical confinement in the core while avoiding the attenuation problems associated with alkali dopants in the cladding regions.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the refractive index profile through selective doping. The core region has higher refractive index due to alkali dopant, while the trench and common cladding have lower refractive indices. This parameter variation creates the necessary optical confinement without excessive attenuation, as the alkali dopant is confined to the core where it is needed for index contrast.
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 achieves an attenuation of less than 0.165 dB/km at 1550 nm, an effective area greater than 75 μm² and less than 135 μm², and counter-propagating crosstalk of less than -40 dB per 100 km, significantly enhancing transmission capacity while maintaining acceptable performance metrics.
Implementation Method 1
a core region extending from the central axis, the core region comprising a relative refractive index Δ1 relative to pure silica, wherein the core region may include an alkali dopant; a trench region encircling the core region, the trench region comprising a relative refractive index Δ3 relative to pure silica, wherein Δ1>ΔCC>Δ3
Data Source
AI summary
An uncoupled multicore optical fiber may include: a common cladding having a refractive index ΔCC and an outer diameter ranging from about 120 μm to about 130 μm; and a plurality of core portions disposed within the common cladding. At least one core portion may include: a central axis; an alkali doped core region extending from the central axis and having a relative refractive index Δ1; a trench region encircling the core region and having a relative refractive index Δ3, wherein Δ1>ΔCC>Δ3; an attenuation less than 0.165 dB/km at 1550 nm; an effective area ranging from about 75 μm2 to about 135 μm2 at 1550 nm; and a cable cutoff wavelength less than or equal to 1530 nm. The common cladding may directly contact the trench region. A counter-propagating crosstalk at 1550 nm between two adjacent core portions may be less than or equal to −40 dB/100 km.