Optical Fiber Outer Cladding Local Stress for Hydrogen Loss
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Solution Overview
Problem
Optical fibers for long-distance communication face transmission loss issues due to strain-induced scattering and glass defect losses, particularly when alkali metal elements are added to the core, as they can lead to nonuniform viscosity and tensile tension in the cladding, causing further strain and loss in transmission performance.
Innovation Solution
An optical fiber design with a silica glass core containing an alkali metal element and a cladding structure featuring an inner and outer cladding layer with different refractive indexes, where the outer cladding layer has a local maximum tensile stress portion within 10 µm of the inner cladding surface, allowing for controlled strain and reaction with hydrogen-derived defects to reduce transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an alkali metal element is added to the core to reduce transmission loss, then transmission loss is reduced, but nonuniform viscosity and tensile tension are generated in the cladding, causing strain and loss in transmission performance
Solution Approach 1:
The patent applies local quality by creating a stressed portion with localized tensile stress in the outer cladding layer, specifically positioned 10 μm or less from the inner cladding surface. This localized stress concentration counteracts the nonuniform viscosity and tensile tension caused by alkali metal addition, thereby maintaining transmission performance while preserving the transmission loss reduction benefits.
Solution Approach 2:
The patent changes the stress distribution parameter by introducing a controlled tensile stress region in the outer cladding layer. By adjusting the position and magnitude of this stressed portion (within 10 μm of the inner cladding surface), the patent optimizes the balance between reducing transmission loss through alkali metal addition and maintaining transmission performance through compensated stress distribution.
2Reliability
If a cladding structure with inner and outer layers is used to control stress distribution, then transmission performance is improved, but device complexity increases
Solution Approach 1:
The patent segments the cladding into an inner cladding layer and an outer cladding layer, with the outer layer containing a localized stressed portion. This segmentation allows independent control of stress distribution in different regions, enabling optimization of transmission performance while maintaining a relatively simple overall structure that can be manufactured using standard optical fiber drawing processes.
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 design effectively suppresses hydrogen-induced transmission loss deterioration, maintaining low loss even in hydrogen-rich environments, thereby reducing cable costs and providing more material options while ensuring reliable performance.
Implementation Method 1
The outer cladding layer includes a local maximum portion where a residual stress, which is a tensile stress, becomes local maximum
Implementation Method 2
an alkali metal element has been added to a core portion is known as an optical fiber for long-distance optical communication requiring transmission loss reduction
Implementation Method 3
The inner cladding layer contains fluorine. The inner and outer cladding layers have refractive indexes different from each other
Data Source
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AI summary
An optical fiber has a structure uniform in a longitudinal direction. This optical fiber includes: a core that includes a silica glass containing an alkali metal element; and a cladding that includes a silica glass and surrounds the core in a cross-section perpendicular to the longitudinal direction. A refractive index of the cladding is lower than a refractive index of the core. The cladding has, in the cross-section, an inner cladding layer having a circular ring shape and including an inner circumferential surface of the cladding, and an outer cladding layer having a circular ring shape and including an outer circumferential surface of the cladding. The inner cladding layer contains fluorine. The inner and outer cladding layers have refractive indexes different from each other. The outer cladding layer includes a local maximum portion where a residual stress, which is a tensile stress, becomes local maximum. A radial distance between the local maximum portion and an inner circumferential surface of the outer cladding layer is 10 µm or less.