Optical Fiber Fluorine Cladding Stress Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical fibers face increased transmission loss due to residual tensile stress in the core, which is not effectively managed by existing technologies, particularly in the distribution of fluorine in the cladding and the use of alkali metals or GeO2, leading to high manufacturing costs and limited drawing speed.
Innovation Solution
An optical fiber design featuring a core and cladding made of silica glass with a fluorine-doped cladding having a controlled refractive index distribution, where the fluorine concentration is minimized in the outermost portion, and a depressed portion between the core and cladding, ensuring a compressive stress in the core and reducing transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the core contains alkali metal element to reduce viscosity and create compressive stress, then the stress in the core becomes compressive, but the manufacturing cost increases due to use of special elements
Solution Approach 1:
The patent changes the chemical composition parameters by replacing alkali metal elements with GeO2 and chlorine in the core, while adjusting fluorine concentration in the cladding. This parameter substitution achieves compressive stress without using expensive alkali metals, resolving the contradiction between stress control and manufacturing cost
Solution Approach 2:
The patent uses common, inexpensive materials (GeO2, chlorine, fluorine) instead of expensive alkali metal elements to achieve the desired stress state. This substitution with cheaper materials reduces manufacturing cost while maintaining the compressive stress effect
2Stress or pressure
If GeO2 is added to the core to create compressive stress, then the stress in the core becomes compressive, but the drawing speed is limited and manufacturing becomes more complex
Solution Approach 1:
The patent optimizes the concentration parameters of GeO2 (0.1-10 wt%) and chlorine (0.1-5 wt%) in the core, combined with fluorine concentration control in the cladding, to achieve compressive stress at standard drawing speeds. This parameter optimization resolves the contradiction between stress control and drawing speed limitation
3Stress or pressure
If fluorine concentration is uniformly distributed in the cladding, then the refractive index is reduced, but the stress distribution cannot be optimized and transmission loss increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform fluorine concentration distribution in the cladding, with higher concentration near the core interface and lower concentration toward the outer surface. This spatial variation in fluorine concentration optimizes both stress distribution and refractive index profile, reducing transmission loss while achieving compressive stress in the core
Solution Approach 2:
The patent changes the fluorine concentration parameter from uniform to gradient distribution in the cladding, with concentration decreasing from the core interface outward. This parameter transformation optimizes the stress profile and refractive index distribution, simultaneously achieving compressive core stress and reduced transmission loss
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An optical fiber according to an embodiment includes a core and a cladding. The average value n1_ave of the refractive index of the core, the minimum value nc_min of the refractive index of the cladding, and the refractive index n0 of pure silica glass satisfy relationships of n1_ave > nc_min and nc_min < n0. The cladding contains fluorine. The fluorine concentration in the cladding is adjusted to be minimum in the outermost portion of the cladding including the outer peripheral surface of the cladding.