Hollow Core Fiber Preform Sealing for Stable Capillary Draw
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Solution Overview
Problem
Manufacturing hollow core optical fibers is challenging due to difficulties in maintaining the relative positioning and dimensions of glass capillary tubes during the drawing process, which is exacerbated by issues with sealing openings in the glass cladding and capillary tubes, leading to potential cracking and uncontrolled gas pressure, resulting in fiber failure.
Innovation Solution
A sealant with a glass composition that matches the thermal expansion coefficient of the glass cladding or capillary tubes is used to seal openings, ensuring controlled gas pressure and maintaining intended dimensions during the drawing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If gas pressure is increased within the glass capillary tubes during draw to stabilize the radius, then the radius is stabilized, but the wall thickness of the glass capillary tubes decreases
Solution Approach 1:
The seal is formed at the openings of the glass capillary tubes and cladding tube before the drawing process begins. This preliminary sealing action prevents gas leakage during the subsequent drawing operation, enabling the gas pressure to be effectively used for stabilizing the capillary tube radius without causing uncontrolled deformation or collapse, thus resolving the contradiction between radius stabilization and wall thickness maintenance.
2Stress or pressure
If openings in the glass cladding and capillary tubes are sealed to control gas pressure, then gas pressure is controlled, but cracking of the glass capillary tubes occurs during draw
Solution Approach 1:
The seal material is specifically designed with a coefficient of thermal expansion that matches the glass composition of the cladding and capillary tubes. This parameter matching ensures that during the heating and drawing process, the seal expands and contracts at the same rate as the glass structures, preventing differential stress and cracking while maintaining effective sealing for gas pressure control.
3Strength
If the seal coefficient of thermal expansion is matched to the glass composition, then cracking is prevented, but the seal must be precisely formulated
Solution Approach 1:
The seal material is formulated with the same base glass composition as the cladding and capillary tubes, creating a homogeneous material system. This homogeneity ensures that the coefficient of thermal expansion is naturally matched, providing crack resistance during thermal cycling while simplifying the manufacturing process by using a standardized glass formulation rather than requiring precise, complex composition adjustments.
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 sealant effectively stabilizes the glass capillary tubes, preventing cracking and ensuring consistent fiber dimensions, thereby enhancing the manufacturing process and performance of hollow core optical fibers.
Implementation Method 1
the sealant effectively stabilizes the glass capillary tubes, preventing cracking and ensuring consistent fiber dimensions
Data Source
AI summary
A hollow core optical fiber preform including a seal at least partially sealing one or more of a cladding opening of a cladding tube and a capillary opening of each or some of one or more capillary tubes within a cladding interior of the cladding tube. The hollow core optical fiber preform includes a seal glass composition exhibiting a seal coefficient of thermal expansion that is within ±10% of a coefficient of thermal expansion of the cladding or a coefficient of thermal expansion of the one or more capillaries. The hollow core optical fiber perform can further include one or more metal tubes extending through the seal. The metal tubes can be placed in fluid communication with one or more sources of a gas to control gas pressure within the one or more capillary tubes and the cladding interior during a draw step to control the dimensions thereof.