Optical Fiber Recoating with Laser-Tapered Stripping

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Solution Overview

Problem

Existing methods for manufacturing long optical fibers, such as submarine cables, face issues with peeling and cracking at the interface between the protective resin and the original coating resin due to stress concentration, particularly when using a two-layer coating structure with a soft primary layer, leading to inconsistent quality and potential damage to the glass fiber.

Innovation Solution

A method involving laser processing to strip the coating layer into a tapered shape, specifically using a laser with a pulse width of 50 fs to 500 ps and a diameter of 100 µm or less, to form a regular polygonal pyramid shape, which disperses stress and increases adhesion with a protective resin, thereby preventing cracks and maintaining fiber quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a two-layer coating structure with a soft primary layer is used, then the optical fiber can withstand bending and twisting stresses, but stress concentration occurs at the interface between the protective resin and the original coating resin, causing peeling and cracking

Engineering Contradiction:
Improveresistance to bending and twisting stressesVSAvoidinterface stability between protective resin and coating resin
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent applies local quality by creating a tapered stripping shape at the end portion of the coating layer, where the coating layer thickness gradually decreases from the base toward the tip. This localized structural modification concentrates the stress-dispersing effect at the critical interface region, allowing the soft primary layer to maintain its shock-absorbing function while the tapered geometry prevents stress concentration at the protective resin interface, eliminating peeling and cracking

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent transitions from a uniform cross-sectional coating structure to a three-dimensional tapered geometry. By extending the coating layer thickness variation along the longitudinal dimension (creating a gradient from base to tip), the solution adds a dimensional aspect that distributes stress along the length of the interface rather than concentrating it at a sharp boundary, thereby improving interface stability

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If the coating layer is stripped uniformly, then the manufacturing process is simple, but stress concentrates at the interface, leading to peeling and cracking of the protective resin

Engineering Contradiction:
Improvesimplicity of coating layer stripping processVSAvoidinterface quality between protective resin and coating resin
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by modifying the geometric parameters of the coating layer stripping shape. Instead of a uniform stripping shape, the invention specifies a tapered shape where the thickness parameter varies continuously from the base to the tip. This parameter variation (gradual thickness reduction) changes the stress distribution pattern, preventing stress concentration while remaining achievable through standard laser processing techniques

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If a laser with a pulse width of 50 fs to 500 ps and a diameter of 100 µm or less is used, then the coating layer is stripped into a precise tapered shape, but the manufacturing process becomes more complex

Engineering Contradiction:
Improveprecision of tapered stripping shapeVSAvoidlaser processing system complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent achieves precise tapered shaping by optimizing specific laser processing parameters: pulse width (50 fs to 500 ps) and beam diameter (100 µm or less). By carefully selecting these parameter ranges, the process achieves high precision in creating the tapered geometry without requiring excessively complex equipment. The parameter optimization balances precision requirements with practical device complexity

Inventive Principle:
Principle #35Parameter changes

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

The method ensures stable optical fiber quality by preventing cracks in the protective resin and reducing damage to the glass fiber, while maintaining consistent adhesion and intensity in the fusion-spliced optical fiber.

Implementation Method 1

a stripping step of irradiating the coating layer with a laser light to strip the coating layer

Methodology Applied
Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

a splicing step of fusion-splicing exposed end surfaces of glass fibers

Methodology Applied
Scientific EffectFusion splicing: Welding

Data Source

PatentEP3757634B1Method for producing optical fiber, and optical fiber
Publication Date: 2025.11.12 SUMITOMO ELECTRIC INDUSTRIES LTD
  • EP3757634B1 patent drawingFigure 1~2C
  • EP3757634B1 patent drawingFigure 3A~3C
  • EP3757634B1 patent drawingFigure 4~6

AI summary

A method for manufacturing an optical fiber, the method including: a stripping step of partially stripping a coating layer 12, 13 of the optical fiber 10; a splicing step of fusion-splicing an exposed end surface of a glass fiber 11; and a recoating step of recoating a protective resin 15 covering a stripped portion of the coating layer 12, 13 and an exposed portion of the glass fiber 11, in which the stripping step irradiates the coating layer 12, 13 with a laser light to strip the coating layer 12, 13. Apulse width of the laser light is 50 fs or more and 500 ps or less.