Optical Fiber Cable Anti-Shrinkage Member Design
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Solution Overview
Problem
Conventional optical fiber cables face issues with material shrinkage leading to fiber protrusion, attenuation, and potential breakage due to the intrinsic post-shrinkage properties of their thermoplastic sheaths, which traditional strength members fail to adequately address.
Innovation Solution
Incorporating anti-shrinkage members with specific dimensions and properties, such as mechanical optical fibers with diameters less than 300 micrometers, embedded within the sheath to control shrinkage and provide strength without additional materials like Aramid Reinforced Plastic or metal, and filling the loose tube with a thixotropic gel to prevent water ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional strength members (metal, glass yarns) are embedded in the sheath to prevent shrinkage, then cable strength is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses optical fibers with different mechanical properties (non-shrinkage fibers) as both the functional element and the strength member, eliminating the need for separate metal or glass yarn strength members. This homogeneous approach using only optical fibers simplifies the overall structure while maintaining strength.
Solution Approach 2:
The patent makes optical fibers serve dual functions: as signal carriers and as strength members to prevent sheath shrinkage. By selecting optical fibers with specific mechanical properties (lower shrinkage than the sheath material), they simultaneously provide both communication and structural support functions.
2Stability of the object's composition
If more traditional strength members are added to counteract shrinkage, then shrinkage resistance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the mechanical parameters of the optical fibers by selecting fibers with specific shrinkage characteristics (lower shrinkage than the thermoplastic sheath). This parameter-based selection allows the fibers themselves to provide shrinkage resistance without adding separate strength members, simplifying manufacturing.
3Stability of the object's composition
If the sheath material with high shrinkage resistance is used, then shrinkage control is improved, but fiber protrusion occurs due to differential shrinkage
Solution Approach 1:
The patent inverts the traditional approach by selecting the optical fiber's shrinkage parameter to be lower than the sheath material's shrinkage parameter. This ensures that during cooling and service, the sheath shrinks more than the fiber, preventing fiber protrusion while still providing overall shrinkage control.
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 effectively reduces fiber protrusion, maintains cable integrity, and enhances mechanical strength while preventing water ingress, resulting in a cost-effective optical fiber cable with optimized stiffness and reduced wastage.
Implementation Method 1
The loose tube is filled with a thixotropic gel to block water ingression
Data Source
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AI summary
Disclosed is an optical fiber cable (100, 200, 300, 400) having a cable core (102) having one or more optical fibers (108), a sheath (104) surrounding the cable core (102), and a one or more anti-shrinkage members (106) embedded in the sheath (104). Each anti-shrinkage member has a length that is substantially equal to a length of the optical fiber cable (100, 200, 300). Further, the anti-shrinkage member has a diameter that is less than 300 micrometres (µm) and does not carry any communication signal.