Optical Cable Sheath Design for Easy Fiber Extraction

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Solution Overview

Problem

The existing optical fiber cables with twisted tensile strength members around a loose tube make it difficult to remove the optical fibers without damaging them, and cutting the tensile strength members is necessary, which reduces workability and increases transmission loss when the cable is bent.

Innovation Solution

An optical cable design with tensile strength members arranged in parallel to the optical fiber unit and a sheath formed between the wrapping tape and the tensile strength members, where the wrapping tape protrudes towards the cable center, allowing easy removal of the sheath and preventing damage to the optical fibers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If tensile strength members are arranged in a twisted state around the loose tube, then the cable structure is stabilized, but the optical fibers become difficult to extract and cutting the tensile strength members is required

Engineering Contradiction:
Improvecable structure stabilityVSAvoidoptical fiber extraction ease
Core Design Contradiction:
Stability of the object's compositionVSEase of operation

Solution Approach 1:

The cable structure is segmented into distinct functional zones: the optical fiber unit is separated from the tensile strength members by the sheath, allowing the optical fibers to be extracted independently without disturbing the twisted tensile strength members. The sheath acts as a separator that divides the cable into an optical fiber-containing portion and a tensile strength member-containing portion.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The sheath is extracted or removed to enable optical fiber extraction. By taking out the sheath that houses both the optical fiber unit and tensile strength members, the optical fibers can be accessed and removed without needing to cut or disturb the tensile strength members, thus resolving the contradiction between structural stability and ease of operation.

Inventive Principle:
Principle #2Taking out (Extraction)

2Device complexity

If tensile strength members are arranged in contact with the optical fiber unit, then the cable structure is simplified, but the optical fibers may be damaged during bending

Engineering Contradiction:
Improvecable structure complexityVSAvoidoptical fiber integrity
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The sheath serves as an intermediary element positioned between the tensile strength members and the optical fiber unit. This intermediary structure prevents direct contact between the tensile strength members and the optical fibers, eliminating the risk of the tensile strength members digging into and damaging the optical fibers during cable bending, while still maintaining a simplified overall cable structure.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Ease of operation

If the sheath is made thin to facilitate fiber extraction, then the extraction process is simplified, but the structural integrity and air-blowing performance are compromised

Engineering Contradiction:
Improvesheath removal easeVSAvoidsheath structural integrity
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The sheath is designed with local quality variations: it has sufficient thickness and strength in regions where structural integrity and air-blowing performance are critical, while allowing for easy removal in regions where fiber extraction is needed. The sheath's design optimizes local properties to satisfy different functional requirements at different locations or stages of cable usage.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP3546999B1Optical cable and outer skin removal method
Publication Date: 2024.03.20 FUJIKURA LTD
  • EP3546999B1 patent drawingFigure 1
  • EP3546999B1 patent drawingFigure 2A~2B
  • EP3546999B1 patent drawingFigure 3

AI summary

[Problem] To provide a new optical cable from which optical fibers are easily taken out. [Solution] An optical cable of the present disclosure includes: an optical fiber unit in which a plurality of optical fibers are wrapped with a wrapping tape; at least three tensile strength members that are arranged on an outer side of the optical fiber unit at intervals in a circumferential direction; and a sheath that coats the optical fiber unit and the tensile strength members, wherein the tensile strength members are arranged in parallel with the optical fiber unit, the sheath is formed between the optical fiber unit and the tensile strength members, an inner wall surface of the sheath formed between the optical fiber unit and the tensile strength members protrudes toward a cable center in comparison with an inner wall surface of the sheath arranged with none of the tensile strength members, and a portion of the wrapping tape arranged on the inner wall surface protruding toward the cable center are depressed toward the cable center.