Optical Fiber Cable With Pre-Elongated Strength Members for Defined Break Load
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Solution Overview
Problem
Existing optical fiber cables with metallic strength members lack pre-elongation, appropriate mechanical characteristics, and defined break loads, leading to uncertainty and high costs, and conventional materials like aramid yarns offer insufficient axial compression resistance and high elongation at break, posing safety risks.
Innovation Solution
The optical fiber cable incorporates stranded metal wires with pre-elongation of 0.02% to 0.1% and embedded under tension, achieving a tensile break load of less than 2100N, elongation at break of less than 2%, and surface roughness of 1um to 5um, ensuring safe and defined breakage under external loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If aramid yarns are used as strength members, then the cable achieves flexibility and ease of installation, but the break load becomes undefined and uncertainty arises in aerial applications
Solution Approach 1:
The patent changes the material parameter from aramid yarn to metallic strength member (steel wire or aluminum alloy wire), which fundamentally alters the mechanical properties. The metallic material provides a defined yield strength and break load, resolving the uncertainty issue while maintaining the flexibility needed for aerial installation through proper wire diameter and strand configuration selection.
Solution Approach 2:
The patent employs composite construction by combining metallic strength members with optical fiber bundles and protective sheathing. This composite structure integrates the high strength and defined mechanical properties of metal with the functional requirements of optical transmission, achieving both reliability and ease of installation.
2Ease of operation
If aramid yarns are used as strength members, then the cable achieves flexibility, but the elongation at break exceeds 2% which poses safety risks
Solution Approach 1:
The patent changes the material from aramid yarn to metallic wires (steel or aluminum alloy) which have controlled elongation properties. By selecting appropriate wire diameter, temper, and strand configuration, the cable achieves elongation within the safe 2% limit while maintaining flexibility for aerial installation through proper mechanical design.
3Reliability
If grp (glass reinforced polymer) strength members are used, then the cable achieves dielectric properties, but the strength to diameter ratio is lower requiring greater outer diameter
Solution Approach 1:
The patent creates a composite cable structure where metallic strength members provide mechanical support and the protective sheathing provides dielectric properties. This composite approach achieves both goals: the metal wires give high strength-to-diameter ratio for compact cable size, while the outer sheath provides the required dielectric protection for aerial installation near power lines.
4Strength
If conventional strength members are used, then the cable achieves basic structural support, but the break load is not pre-defined leading to potential damage to support structures
Solution Approach 1:
The patent changes from conventional materials with undefined break characteristics to metallic wires (steel or aluminum alloy) with well-defined yield strength and break load parameters. This allows engineers to precisely calculate and specify the break load to match the load-bearing capacity of support structures, preventing damage while ensuring adequate strength for aerial installation.
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 provides an optical fiber cable with elongated strength members that safely break under defined loads, reducing the risk of damage to support structures and maintaining structural integrity during aerial installations.
Implementation Method 1
the one or more strength members are elongated by 0.02% - 0.1% in the pre-elongated configuration
Implementation Method 2
The pre-stretching is achieved by applying a stretching force equal to or greater than the predetermined longitudinal break strength of the associated optical fibers
Implementation Method 3
The overhead cables include optical fiber cables that are used for aerial applications... The aerial drop optical fiber cables need to have a predefined break load in order to be installed aerially complying with the safety standards
Data Source
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AI summary
The present disclosure provides an optical fiber cable (100, 200, 300) comprising one or more tubes (104) enclosing at least one optical fiber (102), a sheath (106) surrounding the one or more tubes (104) and one or more strength members (108) embedded in the sheath (106). In particular, the one more strength members (108) are in a pre-elongated configuration and are elongated by 0.02% - 0.1% in the pre-elongated configuration. Additionally, the one or more strength members (108) are embedded at a tension of 1.5-8 kgf and have an elongation at break less than or equal to 2%. Further, the optical fiber cable (100, 200, 300) has a tensile break load of less than 2100N.