W-Profile Optical Fiber for Large Core Area and Low Bending Loss

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing optical fibers face challenges in achieving a large effective core area while maintaining single-mode characteristics and low bending loss, particularly with a cable cut-off wavelength of 1530 nm or less and bending loss of 1 dB/m or less when bent at a diameter of 30 mm.

Innovation Solution

An optical fiber design with a W-shaped refractive index profile, comprising a core portion, a side core layer, a cladding portion, and a coating layer, where Δ1 > ΔClad > Δ2, Δ1 is 0.18% to 0.24%, Δ2 is −0.27% to −0.12%, and b/a is 2.5 to 5, ensuring an effective core area of 105 μm² to 130 μm² and bending loss of 1 dB/m or less.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If the effective core area is increased to suppress nonlinear optical effects, then the optical fiber can be used for long-distance transmission, but the cable cut-off wavelength increases and bending loss worsens

Engineering Contradiction:

Improveeffective core areaVSAvoidcable cut-off wavelength and bending loss

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The optical fiber structure is segmented into multiple functional layers: a core portion, a side core layer with negative refractive index difference, and a cladding portion. This segmentation allows each layer to contribute differently to the overall performance, with the side core layer specifically designed to control the cable cut-off wavelength while the core portion maintains the effective core area for low nonlinear effects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The side core layer is designed with a negative refractive index difference (Δ2 < 0), creating a local region with distinct optical properties. This local quality change allows the fiber to achieve a cable cut-off wavelength of 1530 nm or less while maintaining a large effective core area, resolving the contradiction between area size and wavelength control.

Inventive Principle:

Principle #3Local quality

2Area of moving object

If the effective core area is increased to reduce nonlinear optical effects, then long-distance transmission is enabled, but the single-mode characteristic deteriorates

Engineering Contradiction:

Improveeffective core areaVSAvoidsingle-mode characteristic

Core Design Contradiction:

Area of moving objectVSStability of the object's composition

Solution Approach 1:

The refractive index difference parameter Δ2 in the side core layer is changed to a negative value, which fundamentally alters the waveguide properties. This parameter change enables the fiber to maintain single-mode operation at 1550 nm while achieving an effective core area of 105 μm² or more, thus preventing nonlinear optical effects without sacrificing single-mode characteristic.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the cable cut-off wavelength is reduced to 1530 nm or less, then single-mode characteristic is improved, but the effective core area decreases

Engineering Contradiction:

Improvecable cut-off wavelengthVSAvoideffective core area

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The invention introduces a radial dimension consideration by creating a side core layer at an intermediate radius between the core portion and cladding portion. This dimensional approach allows independent control of the cable cut-off wavelength through the side core layer's refractive index profile, while the overall effective core area is maintained through the combined structure of all layers.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 both single-mode characteristics and low bending loss, with a cable cut-off wavelength of 1530 nm or less and bending loss of 1 dB/m or less, while increasing the effective core area appropriately.

Implementation Method 1

Optical fibers that have a W-shaped refractive index profile have been actively studied

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

When an average maximum relative refractive-index difference of the core portion to an average refractive index of the cladding portion is Δ1, a relative refractive-index difference of an average refractive index of the side core layer to the average refractive index of the cladding portion is Δ2

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS12529839B2Optical fiber

Publication Date: 2026.01.20 FURUKAWA ELECTRIC CO LTD

AI summary

An optical fiber includes: a core portion; a side core layer circumferentially surrounding the core portion; a cladding portion circumferentially surrounding the side core layer; and a coating layer circumferentially surrounding the cladding portion. When an average maximum relative refractive-index difference of the core portion to an average refractive index of the cladding portion is Δ1, a relative refractive-index difference of an average refractive index of the side core layer to the average refractive index of the cladding portion is Δ2, a relative refractive-index difference of the average refractive index of the cladding portion to pure silica glass is ΔClad, Δ1>ΔClad>Δ2 and 0>Δ2 hold, the Δ1 is 0.18% or more and 0.24% or less, the Δ2 is −0.27% or more and −0.12% or less, and (Δ1−Δ2) is 0.36% or more and 0.45% or less.