Asymmetric Optical Fiber Cable Structure for Small-Radius Bending
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Solution Overview
Problem
Optical fiber cables with tensile strength members on both sides of the sheath exhibit bending anisotropy, leading to buckling and difficulty in bending to small diameters, which affects storability and requires a large space for storage.
Innovation Solution
The optical fiber cable design features a tensile strength member provided at one location on the sheath, with a core density of 1.5 core/mm² or more, using materials like fiber reinforced plastic (FRP) with a Young's modulus between 400 MPa and 700 MPa, and a sheath made of ethylene-vinyl acetate copolymer resin (EVA) with a softening point between 40°C and 70°C, allowing for high density fiber mounting and reduced buckling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tensile strength members are provided on both sides of the sheath, then the cable has high tensile strength and anti-buckling property, but the cable exhibits bending anisotropy and tends to buckle when bent to small diameters
Solution Approach 1:
The patent applies asymmetry by providing only one tensile strength member at a specific location on the sheath rather than symmetrically on both sides. This asymmetric configuration eliminates bending anisotropy, allowing the cable to bend uniformly in all directions without buckling, while still maintaining adequate tensile strength through the single strategically positioned member.
Solution Approach 2:
The patent applies local quality by concentrating the tensile strength member at a specific location on the sheath rather than distributing it uniformly. The member is positioned to provide optimal tensile support while minimizing interference with bending operations, achieving local reinforcement without global structural complexity.
2Strength
If tensile strength members are arranged at equal intervals at four locations on the sheath, then the cable has high tensile strength, but the distance between the tensile strength member and bending center is large, causing buckling when bent to small diameters
Solution Approach 1:
The patent reduces the number of tensile strength members from four symmetrically arranged members to a single member positioned asymmetrically on the sheath. This reduction decreases the distance between the tensile strength member and the bending center, enabling the cable to bend to smaller diameters without causing the tensile strength member to buckle.
Solution Approach 2:
The patent extracts unnecessary tensile strength members from the cable structure, retaining only one member that provides sufficient tensile strength while eliminating the structural constraints that prevented small-diameter bending. This extraction simplifies the cable structure and improves bendability.
3Quantity of substance
If the sheath thickness is reduced to increase fiber density, then the cable diameter and weight are reduced, but the tensile strength member is more likely to buckle when the cable is bent
Solution Approach 1:
The patent uses asymmetric positioning of the single tensile strength member on the sheath to compensate for reduced sheath thickness. The member is positioned to provide optimal structural support with minimal material, maintaining buckling resistance even when the sheath is thin enough to allow high fiber density.
Solution Approach 2:
The patent changes the structural parameters by reducing from multiple tensile strength members to a single member and optimizing its position on the sheath. This parameter change allows the use of thinner sheath material while maintaining adequate buckling resistance, thereby enabling higher fiber density.
Data Source
AI summary
An optical fiber cable includes a cable core including a plurality of optical fibers, at least one tensile strength member provided along the cable core, and a sheath configured to cover the cable core from an outside and enclose the tensile strength member. The tensile strength member is provided at one location on the sheath in a cross-sectional view. A core density obtained by dividing the number of the plurality of optical fibers by a cross-sectional area of the cable is 1.5 core/mm2 or more.