Metal-Tube Optical Cable Structure for Fire-Resistant Connectivity

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Solution Overview

Problem

Conventional optical cables fail to meet protection requirements such as fire resistance and circuit integrity in harsh environments, are bulky and expensive, and lack the ability to provide both optical and electrical connectivity in a single cable.

Innovation Solution

An optical cable design featuring a sealed metal tube containing optical fibers, a single-layer polyamide inner sheath, and optional electrically conductive layers, which provides chemical resistance, fire retardancy, and mechanical stability, allowing for reduced thickness and cost while maintaining circuit integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional optical cables use multiple layers and thick protective structures to achieve fire resistance and chemical resistance, then reliability in harsh environments is improved, but device complexity and cost increase

Engineering Contradiction:
Improvefire resistance and chemical resistanceVSAvoidcable structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs composite materials combining polyamide (providing chemical resistance and flame retardancy) with metal strength members (providing mechanical protection and fire resistance). This composite structure achieves the required reliability in harsh environments while maintaining a relatively simple single-layer design compared to conventional multi-layer cables.

Inventive Principle:
Principle #40Composite materials

2Reliability

If conventional optical cables use thick multi-layer protective structures to ensure circuit integrity during fire, then reliability is improved, but cable thickness and cost increase

Engineering Contradiction:
Improvecircuit integrity during fireVSAvoidcable thickness
Core Design Contradiction:
ReliabilityVSLength of stationary object

Solution Approach 1:

The patent changes the material parameters by using polyamide with specific flame retardant properties and controlled thickness (0.5mm to 3mm). This material selection and parameter optimization provide adequate fire resistance and circuit integrity protection while minimizing cable thickness, avoiding the need for thick conventional multi-layer structures.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If conventional optical cables use separate cables for optical and electrical connectivity, then functionality is improved, but device complexity and installation complexity increase

Engineering Contradiction:
Improveoptical and electrical connectivityVSAvoidcable system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges optical fiber pathways and electrical conductor pathways into a single integrated cable structure. The polyamide sheath simultaneously protects both optical fibers and electrical conductors, while metal strength members provide mechanical support for the combined system. This merging reduces installation complexity and enhances versatility compared to using separate cables.

Inventive Principle:
Principle #5Merging (Combining)

4Reliability

If conventional optical cables use multiple protective layers to achieve chemical resistance, then reliability in harsh environments is improved, but manufacturing cost and complexity increase

Engineering Contradiction:
Improvechemical resistanceVSAvoidmanufacturing simplicity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the approach from multiple thin layers to a single thicker layer of polyamide (0.5mm to 3mm) with inherent chemical resistance properties. This parameter change simplifies the manufacturing process by eliminating the need for multiple layering operations while maintaining adequate chemical resistance for harsh environments.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3623854B1Optical cables for harsh environments
Publication Date: 2026.03.25 PRYSMIAN SPA
  • EP3623854B1 patent drawingFigure 1
  • EP3623854B1 patent drawingFigure 2
  • EP3623854B1 patent drawingFigure 3

AI summary

An optical cable includes a plurality of optical fibers sealed within a metal tube, a polymer inner sheath surrounding the metal tube and operatively connected to the metal tube, and an outer sheath disposed over the polymer inner sheath.