Glass Capillary Stress Layer Design for Optical Fiber Insertion
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Solution Overview
Problem
The existing capillaries for holding optical fibers face issues with strength due to thinner wall thickness at the tapered end, and are prone to cracking from microcracks caused by temperature changes and adhesive expansion/shrinkage.
Innovation Solution
A capillary design featuring a compressive stress layer, a tensile stress layer, and a stress-neutral layer, formed through a specific manufacturing process involving laser irradiation, to enhance strength and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the end portion of the capillary is formed in a tapered shape to allow easy insertion of the optical fiber, then the ease of operation is improved, but the wall thickness at the end portion becomes smaller which reduces the strength
Solution Approach 1:
The patent applies local quality by forming a compressive stress layer specifically at the end portion of the capillary where the wall thickness is reduced due to the tapered shape. This localized stress treatment strengthens only the vulnerable end portion without altering the overall tapered geometry needed for easy insertion. The compressive stress layer is created through controlled etching that induces residual compression in the glass structure at the critical thin-walled region.
2Reliability
If the end portion has a microcrack, then the manufacturing precision is compromised, but cracking may occur in the end portion as a result of expansion or shrinkage of the adhesive due to temperature changes
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming a compressive stress layer at the end portion of the capillary before the adhesive is applied. This compressive stress acts as a counterforce that prevents the initiation and propagation of cracks that would otherwise occur due to thermal expansion and shrinkage of the adhesive. The compressive stress layer is created in advance through controlled etching processes that induce residual compression in the glass structure.
3Strength
If a compressive stress layer is formed on the opening portion to prevent cracking, then the strength is improved, but a tensile stress layer is formed at a position away from the compressive stress layer which may be affected by adhesive expansion and shrinkage
Solution Approach 1:
The patent applies local quality by creating a stress distribution profile where the compressive stress layer is concentrated at the opening portion (first end surface) and the tensile stress layer is positioned at the second end surface, away from the adhesive application area. This localized stress arrangement ensures that the critical region subjected to adhesive expansion and shrinkage is dominated by compressive stress rather than tensile stress, thereby preventing crack initiation at the vulnerable end portion.
Solution Approach 2:
The patent applies inversion by positioning the compressive stress layer (which prevents cracking) at the opening portion rather than uniformly distributing stress throughout the capillary. By inverting the typical stress distribution approach and creating a non-uniform stress profile through selective etching, the compressive stress is concentrated where it is most needed - at the end portion with the thinnest walls and highest crack susceptibility.
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 capillary design effectively prevents chipping and cracking at the end portion, reduces the impact of adhesive expansion and shrinkage, and maintains structural integrity under temperature changes.
Implementation Method 1
the first end surface and the opening portion are irradiated with a laser beam having a beam diameter larger than the first end surface
Implementation Method 2
a compressive stress layer, which is formed on the opening portion and is observable by a two-dimensional birefringence measurement method
Implementation Method 3
observable by a two-dimensional birefringence measurement method
Data Source
AI summary
A capillary includes a capillary main body made of glass and formed in an elongated shape. The capillary main body includes an accommodating portion configured to accommodate a part of an optical fiber. The accommodating portion includes an opening portion, which is formed in a first end surface of the capillary main body and is configured to allow insertion of the optical fiber. The capillary main body includes a compressive stress layer, which is formed on an opening portion and is observable by a two-dimensional birefringence measurement method, a tensile stress layer, which is formed at a position away from the compressive stress layer toward a second end surface of the capillary main body and is observable by the two-dimensional birefringence measurement method and a stress-neutral layer, which is formed between the compressive stress layer and the tensile stress layer and is observable by the two-dimensional birefringence measurement method.