Optical Fiber Cable Tear String Positioning for Sheath Removal
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Solution Overview
Problem
The anti-tension member in optical fiber cables prevents downsizing and causes directivity issues in bending, and existing tear strings are difficult to expose and use due to interference with the anti-tension member during sheath cutting, potentially damaging the optical fiber core wire.
Innovation Solution
The optical fiber cable design positions the tear string outside the outer circumscribed lines of multiple anti-tension members, allowing it to be exposed before the anti-tension member during sheath cutting, with a structure that includes multiple strings twisted, braided, or bonded together, and a wave-shaped configuration to facilitate easy extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If multiple anti-tension members are disposed along a symmetric position to reduce cable diameter and bending directivity, then the cable diameter can be downsized and bending directivity can be relieved, but the cutter contacts the anti-tension member before reaching the tear string during sheath cutting
Solution Approach 1:
The tear string is positioned in a different radial dimension relative to the anti-tension members, specifically arranged so that its outer periphery extends beyond the outer circumscribed lines of the anti-tension members in certain cross-sections. This dimensional arrangement allows the cutter to contact the tear string first during sheath cutting, resolving the exposure problem while maintaining the compact symmetric structure of the anti-tension members
Solution Approach 2:
The tear string is pre-positioned to protrude beyond the anti-tension members' outer circumscribed lines before any cutting operation occurs. This preliminary positioning ensures that during sheath cutting, the cutter inevitably contacts the tear string first, automatically exposing it for subsequent tearing operations without requiring additional steps
2Device complexity
If the tear string is positioned inside the anti-tension member, then the structure is compact, but the cutter contacts the anti-tension member first making it difficult to expose and use the tear string
Solution Approach 1:
The tear string is arranged in a radially outer dimension relative to the anti-tension members by positioning its outer periphery beyond their outer circumscribed lines in certain cross-sections. This creates a hierarchical spatial arrangement where the tear string is accessible to the cutter while the anti-tension members remain compact and protective
3Device complexity
If a single thick anti-tension member is used, then the cable structure is simple, but it causes directivity in bending and prevents downsizing
Solution Approach 1:
The anti-tension function is segmented into multiple separate members (typically three or more) arranged symmetrically around the optical fiber core wire. This segmentation eliminates bending directivity by distributing the structural support evenly in all directions, while also enabling cable diameter downsizing compared to a single thick member
Data Source
AI summary
In order to achieve the above-mentioned object, an optical fiber cable according to the present disclosure includes an optical fiber core wire, a sheath covering the optical fiber core wire, three or more anti-tension members inside the sheath, arranged along a longitudinal axis of the optical fiber core wire, and a tear string having an outer periphery a part of which is located outside an outer circumscribed lines of outer peripheries of the three or more anti-tension members in certain cross-sections perpendicular to a longitudinal direction of the sheath, and a part of which comes in contact with an inner periphery of the sheath or is located inside the inner periphery of the sheath in a cross-section perpendicular to the longitudinal direction of the sheath.