Multicore Fiber Connection Method for Reducing Core Distortion

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Solution Overview

Problem

In multicore fiber connections, the convex shaping of end surfaces leads to increased connection loss due to distortion of core positions, making it difficult to accurately shape the fibers without accurately grasping core positions, which is challenging for side surface observation.

Innovation Solution

A multicore fiber connection method that involves shaping the end surfaces by heating them to specific conditions, where the distance from the core to the clad side surface and the inclination angle are controlled to reduce distortion, ensuring the connection loss is minimized by satisfying the expressions 25 ≤ Y ≤ 50 and 0 < X / Y ≤ 0.0054 Y + 0.268, where X is the distance from the end surface to the clad side and Y is the clad thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the end surfaces are heated for shaping, then the minute unevenness on the end surfaces is removed, but the edges and side surface are rounded causing the end surface to become convex, which increases connection loss in multicore fibers

Engineering Contradiction:
Improveend surface flatnessVSAvoidconnection loss
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the heating parameters by controlling the heating amount and duration to achieve a balance where minute unevenness is removed but excessive rounding that causes convexity is prevented. This is done by optimizing the heating conditions based on the relationship between heating amount and end surface shape changes.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional heating-based shaping method with a mechanical cutting method (such as diamond blade cutting or scribe breaking) to shape the end surfaces. This mechanical approach removes material without thermal diffusion, thereby preventing the rounding and convexity formation that occurs with heating while still achieving smooth end surfaces.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If side surface observation is used to grasp core positions, then shaping can be performed, but it is difficult to accurately grasp the positions of the cores

Engineering Contradiction:
Improveshaping operationVSAvoidcore position measurement
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary marking method where external markers or reference features are placed on the fiber surface that correspond to core positions. These markers serve as intermediaries that can be easily observed through side surface inspection, allowing operators to accurately identify core positions without directly observing the cores themselves.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a copy or representation of the core positions on the external fiber surface through manufacturing imprints, laser marking, or alignment features. This copy allows accurate core position identification during shaping operations without requiring direct observation of the embedded cores, thereby improving measurement precision while maintaining ease of operation.

Inventive Principle:
Principle #26Copying

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 reduces connection loss by suppressing core distortion and maintaining consistent end surface conditions, allowing for precise shaping and fusion of multicore fibers, thereby improving the connection quality.

Implementation Method 1

the end surfaces of the optical fibers are fused to each other by causing the pair of electrodes to electrically discharge

Methodology Applied
Scientific EffectHeating: Heating

Implementation Method 2

the end surfaces of the optical fibers are fused to each other by causing the pair of electrodes to electrically discharge

Methodology Applied
Scientific EffectElectrical discharge heating: Electric Arc

Implementation Method 3

the end surfaces of the optical fibers are fused to each other

Methodology Applied
Scientific EffectFusion splicing: Welding

Implementation Method 4

the end surfaces of the optical fibers are fused to each other by causing the pair of electrodes to electrically discharge

Methodology Applied
Scientific EffectThermal fusion: Melting

Data Source

PatentEP3029500B1Multicore fiber connection method
Publication Date: 2023.04.19 FUJIKURA LTD
  • EP3029500B1 patent drawingFigure 1~2
  • EP3029500B1 patent drawingFigure 3~4
  • EP3029500B1 patent drawingFigure 5~6

AI summary

A method of connecting multicore fibers 2 includes a shaping step S2 of shaping end surfaces 50 to be connected of the multicore fibers 2 by heating the end surfaces 50 of the multicore fibers and a fusing step S3 of fusing the shaped end surfaces 50 to each other. The multicore fibers 2 satisfy Y ≥ 20, where a distance from a center of a core 11 located on the outer periphery side of a clad 20 to a side surface of the clad 20 is defined as Y µm. The shaping step S2 includes heating the end surfaces 50 to satisfy 0 &lt; X/Y ≤ 0.0054Y + 0.268, where a distance in a longitudinal direction from a portion of each multicore fiber 2 located at an end in the longitudinal direction on each shaped end surface 50 to a position at which the end surface 50 and the side surface of the clad 20 meet each other is defined as X µm.