Multicore Fiber With Compressive Stress to Reduce Transmission Loss
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Solution Overview
Problem
Multicore fibers manufactured using the perforation method experience increased transmission loss due to tensile stress concentrated at the cladding portion, which affects the core portions.
Innovation Solution
A multicore fiber design that applies compressive stress to first glass regions, including a configuration with first and second glass regions and a cladding region, where the average compressive stress in the first glass regions is lower than in the second glass region, reducing stress concentration on the core portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the perforation method is used to manufacture multicore fiber preform, then the manufacturing process is simplified and productivity is improved, but tensile stress is concentrated at the cladding portion causing increased transmission loss
Solution Approach 1:
The patent changes the stress state parameter from tensile to compressive by introducing a compressive stress layer surrounding the core portions. This parameter change directly addresses the transmission loss issue caused by tensile stress concentration while maintaining the perforation method's manufacturing advantages.
Solution Approach 2:
The patent converts the harmful tensile stress concentration into a beneficial compressive stress state by adding a compressive stress layer. This layer transforms the stress condition from harmful (tensile) to beneficial (compressive), reducing transmission loss while keeping the manufacturing process efficient.
2Ease of manufacture
If heat treatment is applied to integrate cladding rod and core rods, then the multicore fiber preform is formed, but tensile stress is generated due to thermal contraction of the cladding portion
Solution Approach 1:
The patent applies preliminary anti-action by introducing a compressive stress layer before the fiber is subjected to use conditions. This pre-applied compressive stress counteracts the tensile stress that would otherwise be generated during heat treatment and thermal contraction, preventing transmission loss without modifying the heat treatment process itself.
Solution Approach 2:
The patent creates a composite stress state by combining the inherent tensile stress from heat treatment with an additional compressive stress layer. This composite approach allows the beneficial compressive stress to dominate, reducing net tensile stress and transmission loss while maintaining the simplicity of the heat treatment integration process.
3Reliability
If compressive stress is applied to first glass regions, then transmission loss is reduced, but the stress distribution becomes more complex
Solution Approach 1:
The patent applies local quality by introducing compressive stress specifically in the regions surrounding the core portions (first glass regions), rather than uniformly throughout the entire fiber structure. This localized application of compressive stress reduces transmission loss at the critical core-cladding interface without unnecessarily complicating the overall stress distribution in non-critical regions.
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 design effectively reduces transmission loss to approximately the same level as single-core optical fibers by minimizing tensile stress on the core portions, thereby preventing an increase in light propagation loss.
Implementation Method 1
tensile stress is concentrated at the side of the cladding portion in the plurality of core portions due to an influence of thermal contraction or the like of the cladding portion
Data Source
AI summary
A multicore fiber includes: a plurality of first glass regions each including: a core portion; and a first cladding portion having a lower refractive index than a maximum refractive index of the core portion; and a cladding region formed on outer peripheries of the plurality of first glass regions, wherein compressive stress is applied to the plurality of first glass regions.