Optical Fiber Cable Segmented Fire-Resistant Design
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Solution Overview
Problem
Existing optical communication cables face challenges in supporting a large number of optical fibers within a small space while maintaining fire resistance and low latency/skew characteristics, as the increased fiber count often compromises burn resistance and tension distribution.
Innovation Solution
The optical communication cable design features a three-tiered structure with fire-resistant materials, including a cable jacket, bundle jacket, and subunit jacket, along with differential tensile strength strands and wrapping patterns to ensure equal optical fiber lengths and even tension distribution, allowing for high fiber density and low skew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the fiber count is increased to support more optical fibers within the cable, then the capacity and functionality are improved, but the fire resistance and tension distribution are compromised
Solution Approach 1:
The cable is divided into multiple independent subunits, each containing a limited number of optical fibers (e.g., 12 fibers per subunit). These subunits are individually jacketed and then bundled together, creating a segmented structure that maintains fire resistance while accommodating high fiber counts (e.g., 144, 192, or more fibers in the entire cable). The segmentation allows fire containment within individual subunits rather than compromising the entire cable.
Solution Approach 2:
The cable employs a nested hierarchical structure where optical fibers are contained within subunit jackets, which are then contained within bundle jackets, which are finally contained within the outer cable jacket. This nested arrangement (fibers → subunits → bundles → cable) enables high fiber density while maintaining fire resistance at each hierarchical level, as fires would be contained within the innermost subunit layers.
2Quantity of substance
If the fiber count is increased to support more optical fibers within the cable, then the capacity and functionality are improved, but the cable dimensions and space requirements worsen
Solution Approach 1:
By segmenting the cable into compact subunits with their own jackets, the design achieves high fiber density without proportionally increasing overall cable dimensions. Multiple subunits are efficiently packed within the cable cross-section, allowing 144, 192, or even higher fiber counts while maintaining manageable cable outer diameters suitable for indoor data center applications.
Solution Approach 2:
The nested hierarchical structure (fibers within subunits within bundles within cable) maximizes space utilization. Each hierarchical level is tightly packed within the next level, creating a compact configuration that accommodates high fiber counts without excessive increase in cable volume or outer dimensions.
3Strength
If traditional tensile strength members are used, then structural support is provided, but uneven tension distribution and latency skew occur
Solution Approach 1:
Tensile strength members are placed locally within each subunit rather than as a single centralized element. Each subunit contains its own tensile strength member positioned adjacent to the optical fibers it protects. This local placement ensures that tension forces are distributed evenly across all subunits and fibers, preventing latency skew while providing adequate structural support for the entire cable.
Solution Approach 2:
The distributed placement of tensile strength members within each subunit creates equipotential tension distribution across all optical fibers in the cable. By ensuring that each fiber experiences similar tension conditions through its local tensile strength member, the design minimizes latency differences (skew) between fibers while maintaining overall cable strength.
Data Source
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AI summary
An optical communication cable is provided. The optical communication cable includes an outer cable layer and a plurality of optical fiber bundles surrounded by the outer cable layer. Each optical fiber bundle includes a bundle jacket surrounding a plurality of optical fiber subunits located within the bundle passage. The plurality of optical subunits are wrapped around each other within the bundle passage forming a wrapped pattern. Each optical fiber subunit includes a subunit jacket surrounding a elongate optical fiber located within the subunit passage. The cable jacket, bundle jacket and subunit jacket may be fire resistant, and strength strands of differing lengths may be located in the bundles and the subunits.