Alternating-Trench Multicore Fiber Layout for Low Crosstalk

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Solution Overview

Problem

Existing multicore optical fibers face challenges with high crosstalk, sensitivity to dispersion, complex and costly manufacturing, and limited core density due to the use of trench regions and buffer regions, which affect signal transmission and increase costs.

Innovation Solution

A multicore fiber design featuring a cladding region with alternating trench-assisted and non-trenched core regions, arranged in a predefined lattice, with specific refractive index profiles and radial distances, eliminating buffer regions and optimizing core arrangement to reduce crosstalk and manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If trench regions are formed around each core to control crosstalk, then crosstalk is reduced, but manufacturing cost and complexity increase

Engineering Contradiction:
ImprovecrosstalkVSAvoidmanufacturing complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention segments the trench regions into selective portions between adjacent cores rather than forming complete circular trenches around each core. This partial trench approach reduces manufacturing complexity while maintaining effective crosstalk isolation between cores.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention applies trench regions only in specific local areas where crosstalk occurs between adjacent cores, rather than uniformly around all cores. This localized approach reduces overall device complexity while maintaining crosstalk control where needed.

Inventive Principle:
Principle #3Local quality

2Object-affected harmful factors

If trench regions are formed around each core to control crosstalk, then crosstalk is reduced, but manufacturing cost increases

Engineering Contradiction:
ImprovecrosstalkVSAvoidmanufacturing cost
Core Design Contradiction:
Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The trench regions are segmented into partial regions rather than complete circles, reducing the amount of material removal and processing required, thereby lowering manufacturing cost while maintaining crosstalk control.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention extracts only the necessary portions of trench regions that are needed for crosstalk control, removing unnecessary trench formations that would increase manufacturing cost without providing additional benefit.

Inventive Principle:
Principle #2Taking out (Extraction)

3Ease of manufacture

If buffer regions are included around each core, then manufacturing is simplified, but core density decreases

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidcore density
Core Design Contradiction:
Ease of manufactureVSQuantity of substance

Solution Approach 1:

The invention removes the buffer regions that were traditionally included around each core, extracting only the essential trench portions needed for crosstalk control, thereby increasing core density while maintaining manufacturing feasibility.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of adding buffer regions around each core and then adding trenches, the invention inverts the approach by directly forming selective trench portions between cores without buffer regions, achieving both high density and manufacturing simplicity.

Inventive Principle:
Principle #13The other way round (Inversion)

4Productivity

If the number of cores is increased to reduce bandwidth limitations, then bandwidth increases, but crosstalk increases

Engineering Contradiction:
ImprovebandwidthVSAvoidcrosstalk
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The selective partial trench segmentation allows closer core spacing needed for high core density and bandwidth while maintaining effective crosstalk isolation through strategically placed trench portions between adjacent cores.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

By applying trench regions only in specific locations between adjacent cores rather than uniformly around all cores, the invention enables higher core density for increased bandwidth while controlling crosstalk only where it occurs between neighboring cores.

Inventive Principle:
Principle #3Local quality

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 design achieves reduced crosstalk, improved signal confinement, and lower manufacturing costs while maintaining high core density and efficient signal transmission, with a cable cut-off wavelength of less than 1260 nm and crosstalk of less than -25 dB/10 Km.

Implementation Method 1

Optical fibers are strands of glass fiber processed so that light beams transmitted through the glass fiber are subject to total internal reflection wherein a large fraction of the incident intensity of light directed into the fiber is received at the other end of the fiber

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

Each of the plurality of trench-assisted core regions are defined by a plurality of core regions and a plurality of trench regions surrounding the plurality of core regions

Methodology Applied
Scientific EffectRefraction: Refraction

Data Source

PatentEP4700446A1Multicore fiber having alternated cores with and without trench
Publication Date: 2026.02.25 STERLITE TECHNOLOGIES LTD
  • EP4700446A1 patent drawingFigure 1A
  • EP4700446A1 patent drawingFigure 1B
  • EP4700446A1 patent drawingFigure 2A

AI summary

The present disclosure provides multicore fiber (100, 200, 300) with a cladding region (106), a plurality of non-trenched core regions (104), and a plurality of trench-assisted core regions (102) such that the plurality of non-trenched core regions (104) and the plurality of trench-assisted core regions (102) are arranged in a predefined lattice in the cladding region. Each of the plurality of trench-assisted core regions (102) are defined by a core region (108) and a trench region (110) surrounding the core region (108) such that a radial thickness of an un-doped region between the core region (108) and the trench region (110) is less than 1 micrometres (µm).