Multicore Optical Coupler Layout for Uniform Core Coupling

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Solution Overview

Problem

In optical communication systems using multicore optical fibers, the coupling ratios between the cores of single-core optical fibers and multicore optical fibers are uneven due to markers with different refractive indices, leading to inconsistent signal transmission.

Innovation Solution

The optical coupler is designed to minimize the differences in coupling ratios by carefully polishing and fusing the cladding of multicore and single-core optical fibers, ensuring that each core of the single-core fibers is coupled to a specific core of the multicore fiber that is not affected by the marker, thereby maintaining consistent signal transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If markers are provided in the cladding of MC optical fiber to distinguish/identify cores, then core identification is enabled, but coupling ratio uniformity deteriorates due to refractive index differences

Engineering Contradiction:
Improvecore identificationVSAvoidcoupling ratio uniformity
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a localized low-refractive-index region only at the coupling interface between the MC optical fiber and SC optical fiber, rather than using markers throughout the entire MC fiber. This localized modification affects only the coupling region, minimizing interference with the marker's identification function while improving coupling uniformity.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent introduces an intermediary low-refractive-index region between the MC optical fiber core and SC optical fiber core to mediate the coupling process. This intermediary region acts as a buffer that equalizes the refractive index environment at the coupling interface, reducing the impact of marker-induced refractive index variations on coupling ratio uniformity.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If cores of SC optical fibers are disposed close to one core of MC optical fiber, then optical coupling is achieved, but coupling ratio differences occur due to marker proximity

Engineering Contradiction:
Improvesignal transmission consistencyVSAvoidcoupling structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating a localized low-refractive-index region only at the coupling interface between the MC optical fiber and SC optical fiber, rather than using markers throughout the entire MC fiber. This localized modification affects only the coupling region, minimizing interference with the marker's identification function while improving coupling uniformity.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent changes the refractive index parameter locally at the coupling interface by creating a low-refractive-index region. This parameter change compensates for the refractive index variations caused by nearby markers, thereby equalizing the coupling ratios without requiring complex structural modifications.

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

This approach ensures uniform coupling ratios across all cores, enhancing the reliability and efficiency of signal transmission in multicore optical communication systems.

Implementation Method 1

polishing and fusing the cladding of multicore and single-core optical fibers

Methodology Applied
Scientific EffectFusion: Welding

Implementation Method 2

The marker has a refractive index different from those of the cores and the cladding, and thus the coupling ratio between a core disposed close to the marker

Methodology Applied
Scientific EffectRefraction: Refraction

Data Source

PatentEP4064468B1Optical coupler and optical amplifier
Publication Date: 2026.02.11 KDDI CORP
  • EP4064468B1 patent drawingFigure 1~3
  • EP4064468B1 patent drawingFigure 4A~4B
  • EP4064468B1 patent drawingFigure 5

AI summary

An optical coupler includes first to Nth members, wherein a Kth (K is an integer of 1 to N) member includes a MC optical fiber including first to Pth (P is an integer of N or greater) cores disposed at regular intervals in a circular shape, and a marker disposed at a position closest to the first core, and at least one SC optical fiber, a core of the SC optical fiber of the Kth member is coupled to a coupled core that is other than the first core, cores of the MC optical fiber of an Mth (M is an integer of 1 to N-1) member are connected to cores of the MC optical fiber of an (M+1)th member, a total number of SC optical fibers included in the first to Nth members is P, and each of P cores of the MC optical fibers configured through the connection of the first to Nth members is connected to a core of one of the P SC optical fibers included in the first to Nth members.