Central Loose Tube Optical-Fiber Cable Shrinkage Stress
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Solution Overview
Problem
Optical-fiber cables with rigid strength members are impractical for flexible deployments and are vulnerable to excessive temperature-induced shrinkage, leading to optical-fiber attenuation, necessitating a solution that balances flexibility and strength while minimizing shrinkage forces.
Innovation Solution
A central loose tube optical-fiber cable design featuring non-rigid strength systems with stranded strength yarns surrounding a polymeric buffer tube and a low-shrinkage cable jacket, eliminating rigid strength members and preferential bending axes, and incorporating thixotropic materials for water-blocking and mechanical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid strength members are included to withstand mechanical stresses and thermal expansion, then cable strength and stability are improved, but cable flexibility and adaptability to different deployment configurations deteriorate
Solution Approach 1:
The patent changes the physical state and mechanical properties of the strength members by using extruded polymeric strength members instead of rigid members. These polymeric members have temperature-dependent mechanical properties that allow them to be rigid at operating temperatures while remaining flexible during installation, thus resolving the contradiction between strength and flexibility
Solution Approach 2:
The patent employs composite construction by combining polymeric strength members with optical fibers in a shared tube structure. The composite system leverages the tensile strength of the polymeric members while allowing the overall cable structure to achieve flexibility through the viscoelastic properties of the polymer material
2Adaptability or versatility
If rigid strength members are excluded to improve flexibility, then cable adaptability is improved, but vulnerability to temperature-induced shrinkage and optical-fiber attenuation increases
Solution Approach 1:
The patent utilizes the temperature-dependent parameter changes of extruded polymeric strength members, which exhibit increased rigidity and strength at lower temperatures (below freezing) compared to their state at operating temperatures. This allows the cable to resist temperature-induced shrinkage and prevent optical-fiber attenuation while maintaining flexibility during installation
Solution Approach 2:
The patent implements beforehand cushioning by incorporating extruded polymeric strength members that are pre-configured to provide mechanical support and cushioning against thermal shrinkage forces before temperature-induced stress occurs, thereby protecting the optical fibers from attenuation
3Strength
If extruded polymeric strength members are used to provide temperature-dependent mechanical properties, then cable strength at low temperatures is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing extruded polymeric strength members that simultaneously perform multiple functions: providing tensile strength, resisting thermal shrinkage, enabling cable flexibility during installation, and protecting optical fibers. This multi-functionality reduces overall cable structure complexity while achieving superior low-temperature strength
Solution Approach 2:
The patent utilizes parameter changes in the polymeric material's mechanical properties with temperature to achieve different functional requirements at different temperatures, eliminating the need for separate rigid and flexible strength member components and thereby reducing structural complexity
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 achieves less than 0.3% excess fiber length at 23°C and reduced shrinkage stress of 12 MPa or less at -40°C, enhancing flexibility and maintaining low optical-fiber attenuation, thus addressing the challenges of temperature-induced shrinkage and mechanical stress.
Implementation Method 1
loose tube optical-fiber cables are vulnerable to excessive temperature-induced shrinkage (e.g., below freezing, such as between about -20°C and -40°C)
Implementation Method 2
The non-rigid strength system includes stranded strength yarns that surround a polymeric buffer tube and one or more optical fibers positioned within the polymeric buffer tube's annular space
Implementation Method 3
incorporating thixotropic materials for water-blocking and mechanical coupling
Data Source
Figure 1
AI summary
The present invention relates to central loose optical-fiber cables. An exemplary optical-fiber cable includes a central buffer tube that encloses loose optical fibers. Stranded strength yarns surround the central buffer tube and the optical fibers positioned within the central buffer tube's annular space, and a cable jacket surrounds the stranded strength yarns.