Optical Fiber Cable Resin-Reinforced Overlaps Against Sheath Cracking

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Solution Overview

Problem

Existing optical fiber cables face issues with sheath cracking due to weak adhesive forces at overlapping portions of the reinforcing member, leading to stress concentration when bent.

Innovation Solution

A production method involving winding a reinforcing member with overlapping end portions and inserting resin into these overlapping portions during extrusion molding to enhance adhesive strength and resistance against bending forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If adhesive is applied to join overlapping portions of the reinforcing member, then the reinforcing member can be formed, but the adhesive force may be weak at certain portions leading to sheath cracking

Engineering Contradiction:

Improveforming of reinforcing memberVSAvoidadhesive force at overlapping portion

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The resin is inserted into the overlapping portion before the extrusion molding is completed. This preliminary insertion ensures that the resin is already in position to provide reinforcement and prevent sheath cracking at the critical adhesive weak points during subsequent bending or stress applications.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent combines the reinforcing member (metal or composite strip) with resin material in a composite structure. The resin is inserted into the overlapping portion and cured to form a reinforced joint, creating a composite structure that leverages the strength of both materials to prevent sheath cracking while maintaining manufacturability.

Inventive Principle:

Principle #40Composite materials

2Strength

If the reinforcing member is wound around the core, then the structural integrity is improved, but stress concentration occurs at overlapping portions when bent

Engineering Contradiction:

Improvestructural integrityVSAvoidstress concentration at overlapping portion

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The resin is inserted into the overlapping portion beforehand to act as a cushioning element. This pre-inserted resin provides a buffer that distributes stress away from the adhesive joint and the overlapping portion during bending, preventing stress concentration that would otherwise cause sheath cracking.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The resin is selectively inserted only into the overlapping portion of the reinforcing member, creating a localized reinforcement zone. This local quality enhancement provides targeted stress distribution and reinforcement exactly where the stress concentration occurs during bending, without affecting the rest of the cable structure.

Inventive Principle:

Principle #3Local quality

3Reliability

If resin is inserted into the overlapping portion during extrusion molding, then sheath cracking is suppressed, but the manufacturing process becomes more complex

Engineering Contradiction:

Improveresistance to sheath crackingVSAvoidextrusion molding process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The resin insertion is performed as a preliminary action before the final extrusion molding step. By inserting the resin into the overlapping portion beforehand and allowing it to cure or set, the process ensures reliable stress distribution and prevents sheath cracking while integrating smoothly into the existing extrusion molding workflow.

Inventive Principle:

Principle #10Preliminary action

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

This method effectively suppresses sheath cracking by increasing the resistance force at overlapping portions, ensuring the optical fiber cable's durability and integrity, even in high-temperature environments.

Implementation Method 1

an adhesive is applied onto both end portions of the strip-shaped material... the overlapping portions of the reinforcing member are joined by the adhesive

Methodology Applied

Scientific EffectAdhesive: Adhesive

Implementation Method 2

the reinforcing member is introduced into an extruder and is caused to pass through the extruder. In this manner, the reinforcing member is coated with a resin to form the sheath

Methodology Applied

Scientific EffectExtrusion: Extrusion

Data Source

PatentUS20250231360A1Optical fiber cable production method, and optical fiber cable

Publication Date: 2025.07.17 FUJIKURA LTD

AI summary

An optical fiber cable includes: a core including optical fibers; a reinforcing wrap that surrounds the core; and a sheath that accommodates the core and the reinforcing wrap. The reinforcing wrap includes an overlapping portion. A first end portion of the reinforcing wrap overlaps a second end portion of the reinforcing wrap at a portion of the reinforcing wrap in a circumferential direction of the optical fiber cable in a cross-sectional view.