Multicore Fiber Cladding Stress Control for Higher Rupture Strength
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Solution Overview
Problem
Multicore fibers manufactured using conventional hole drilling methods often exhibit lower rupture strength compared to single-mode optical fibers, necessitating a solution for enhancing their mechanical integrity.
Innovation Solution
The multicore fiber design incorporates a cladding portion with specific stress and softening point regions, including a second-type region with tensile stress of 20 MPa or lower on the outer periphery and a low softening point, combined with a manufacturing method that maintains precise core positioning and allows for larger preform sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hole drilling method is used to manufacture multicore fiber, then multicore fiber can be manufactured, but rupture strength is lower compared to single-mode optical fiber
Solution Approach 1:
The cladding portion is designed with non-uniform tensile stress distribution, where the outer peripheral region has reduced tensile stress (20 MPa or lower) compared to the inner region. This local stress optimization protects the outer cladding from crack initiation while maintaining overall structural integrity and manufacturability through the hole drilling method.
Solution Approach 2:
The patent optimizes the tensile stress parameter in the cladding portion by controlling the refractive index distribution and mechanical properties of the cladding material. By adjusting the tensile stress to 20 MPa or lower in the outer peripheral region, the rupture strength is enhanced while preserving the effectiveness of the hole drilling manufacturing process.
2Stability of the object's composition
If cladding portion has high tensile stress on outer periphery, then structural integrity is maintained, but rupture strength decreases due to crack initiation
Solution Approach 1:
The cladding portion exhibits spatially varying tensile stress characteristics, with the outer peripheral region specifically engineered to have reduced tensile stress (≤20 MPa). This local stress modification prevents crack initiation at the vulnerable outer surface while the inner cladding regions maintain sufficient stress for structural integrity.
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 results in a multicore fiber with enhanced rupture strength, equivalent to standard single-mode fibers, while maintaining high positional accuracy and flexibility in design, reducing manufacturing challenges, and increasing the preform's size without complexity.
Implementation Method 1
the cladding portion has tensile stress of 20 MPa or lower in a region on outer periphery side than a core portion that is closest to outer periphery of the cladding portion
Implementation Method 2
the cladding portion has a low softening point region on outer periphery side of a core portion that is closest to outer periphery of the cladding portion
Data Source
AI summary
A multicore fiber includes: a plurality of core portions made of glass; and a cladding portion made of glass and configured to surround outer periphery of the plurality of core portions. The cladding portion has tensile stress of 20 MPa or lower in a region on outer periphery side than a core portion that is closest to outer periphery of the cladding portion in the plurality of core portions.