Gap-Free Fiber Laser Combiner Fusion to Prevent Feedback Breakage

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Solution Overview

Problem

Fiber laser devices experience combiner breakage due to optical feedback, which causes heat generation and damage from gaps between input fibers and bridge fibers in fusion-spliced portions.

Innovation Solution

A combiner configuration where input fibers are bundled and fused without gaps at the interface with a relay fiber, with a larger outer diameter of the relay fiber's clad creating a level difference to direct optical feedback outside, and no tubular member is used to facilitate gap-free fusion and prevent heat-induced breakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bundle portion with fusion-spliced input fibers and bridge fiber is used in the combiner, then optical combination is achieved, but gaps between input fibers allow optical feedback to leak and strike coatings causing heat generation and breakage

Engineering Contradiction:

Improvecombiner durabilityVSAvoidoptical feedback leakage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The harmful gap between input fibers is eliminated by extracting the problematic fusion-spliced structure and replacing it with a melted integrated structure where input fibers are fused together without gaps, preventing optical feedback leakage while maintaining optical combination functionality

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The combiner uses a composite structure where input fibers are melted and integrated together to form a unified glass portion, creating a gap-free interface that prevents optical feedback from reaching the coatings, thereby resolving the contradiction between maintaining optical combination and preventing harmful feedback leakage

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If the outer diameter of relay fiber clad is larger than melting portion, then level difference is formed to direct optical feedback outside, but structural complexity increases

Engineering Contradiction:

Improveoptical feedback escapeVSAvoidcombiner structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The combiner utilizes a level difference created by the curvature and diameter variation between the relay fiber clad and the melting portion, forming a graded interface that naturally directs optical feedback outward without requiring additional complex structural elements

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The interface between the relay fiber and melting portion is designed with localized varying properties (different outer diameters creating level difference), allowing optical feedback to be directed outward at this specific location while maintaining simple overall structure

Inventive Principle:

Principle #3Local quality

3Strength

If tubular member is used to attach input fibers, then structural support is provided, but optical feedback can reach near coatings causing heat generation

Engineering Contradiction:

Improvefiber attachment supportVSAvoidoptical feedback heat generation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The tubular member that caused optical feedback issues is completely removed from the design. Instead, input fibers are attached and supported through direct melting and integration, forming a unified glass structure that provides both mechanical support and prevents optical feedback leakage simultaneously

Inventive Principle:

Principle #2Taking out (Extraction)

4Object-affected harmful factors

If input fibers are melted and integrated without gap, then optical feedback leakage is prevented, but manufacturing precision requirements increase

Engineering Contradiction:

Improvegap-free fusionVSAvoidmelting integration accuracy

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The manufacturing process utilizes the phase transition of glass from solid to liquid and back to solid through controlled melting. By heating the input fibers to their melting point and then allowing them to cool and solidify, the process naturally forms a gap-free integrated structure, reducing the need for high-precision mechanical alignment compared to traditional fusion splicing

Inventive Principle:

Principle #36Phase transitions

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

Prevents combiner breakage by eliminating optical feedback leakage and heat generation, maintaining uniform numerical aperture and reducing light loss, while allowing optical feedback to escape and avoiding damage to the input fibers.

Implementation Method 1

a melting portion at which the plurality of input fibers are melted and integrated together

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

outer circumferences of glass portions (outer circumferences of clads) of the plurality of input fibers fuse together without a gap

Methodology Applied

Scientific EffectFusion: Nuclear Fusion

Data Source

PatentUS11005230B2Combiner, fiber laser device, and method for manufacturing combiner

Publication Date: 2021.05.11 FUJIKURA LTD

AI summary

A combiner, that optically combines input fibers that propagate pumping light launched from pumping light sources and a relay fiber connected to an amplification fiber, includes: a bundle portion where the input fibers are bundled together; and a melting portion where the input fibers are melted and integrated together. In an interface between the relay fiber and the melting portion, the input fibers are fused together without a gap between the input fibers.