Hollow Core Fiber Preform Redraw for Capillary Aspect Ratio Control
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Solution Overview
Problem
Manufacturing anti-resonant hollow core optical fibers (AR-HCFs) is challenging due to the difficulty in achieving the exact structural requirements of anti-resonant cladding elements, particularly the capillary dimensions, which are sensitive to manufacturing variability and require precise thickness and radius during the drawing process.
Innovation Solution
A redraw step is applied to a preform precursor, manipulating gas pressure within capillaries while heating to alter the aspect ratio, allowing for more precise control of capillary dimensions, reducing the need for further adjustments during the drawing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If anti-resonant cladding elements with precise capillary dimensions are manufactured directly without redraw step, then manufacturing process is simpler, but capillary dimensional precision is insufficient due to manufacturing variability
Solution Approach 1:
The patent applies a redraw step before the final drawing process to preliminarily adjust and stabilize the capillary dimensions. By performing this intermediate shaping operation, the capillaries achieve their target dimensions with tighter tolerances, reducing the need for complex post-adjustment mechanisms during drawing.
Solution Approach 2:
The patent changes physical parameters during the redraw step, specifically controlling temperature and pressure conditions to alter the glass viscosity and enable precise dimensional adjustment of capillaries. This parameter control allows the capillary aspect ratio to be tuned to achieve the desired dimensional precision.
2Manufacturing precision
If capillary dimensions are adjusted during drawing process, then dimensional precision can be improved, but manufacturing complexity and difficulty increase
Solution Approach 1:
The redraw step performs the dimensional adjustment in advance, before the drawing process begins. This preliminary action sets the capillary dimensions close to the target values, so that minimal adjustment is needed during drawing, greatly simplifying the overall manufacturing process.
Solution Approach 2:
The manufacturing process is segmented into distinct steps: initial preform fabrication, redraw step for dimensional adjustment, and final drawing. This segmentation allows each step to be optimized independently, with the redraw step specifically dedicated to achieving precise capillary dimensions.
3Manufacturing precision
If redraw step with gas pressure manipulation is applied, then capillary dimensional precision is improved, but process time and complexity increase
Solution Approach 1:
The patent manipulates gas pressure as a controllable parameter during the redraw step to achieve precise capillary dimensional control. By adjusting the gas pressure, the internal support pressure changes, enabling fine-tuning of capillary thickness and radius. This parameter control achieves high precision without requiring excessively long processing times.
Solution Approach 2:
The redraw step utilizes the phase transition or viscosity change of glass at elevated temperatures to enable dimensional adjustment. By heating the glass to a softened state and then controlling the cooling rate along with gas pressure, the capillary dimensions can be precisely set in a relatively short time compared to conventional methods.
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 redraw step ensures that the capillary dimensions are accurately set, facilitating easier and more consistent production of AR-HCFs with improved confinement of electromagnetic radiation, reducing manufacturing complexity and enhancing performance.
Implementation Method 1
heating at least a portion of a workpiece comprising: (a) a cladding tube... (b) one or more capillaries disposed within the cladding interior... wherein the workpiece is in fluid communication with one or more of a source of gas and a vacuum, and (2) manipulating a gas pressure within the capillary interior
Implementation Method 2
manipulating a gas pressure within the capillary interior of at least one of the one or more capillaries or the cladding interior, via the source of gas or the vacuum, to vary the aspect ratio of the at least one of the one or more capillaries
Implementation Method 3
the redraw step produces one or more preforms from the workpiece... wherein the redraw step ensures that the capillary dimensions are accurately set
Data Source
AI summary
A method of manufacturing a preform for a hollow core optical fiber including: a redraw step including: (1) heating a workpiece including: (a) a cladding tube including (i) a cladding interior, (ii) a cladding outer surface at a cladding outer radius, and (iii) a cladding thickness; and (b) a capillary disposed within the cladding interior, the capillary including (i) a capillary interior, (ii) a capillary outer radius, (iii) a capillary inner radius, (iv) a capillary thickness, and (v) a capillary aspect ratio corresponding to the ratio of the capillary inner radius to the capillary outer radius, and (2) manipulating a gas pressure within the capillary interior or the cladding interior, via a source of gas or a vacuum, to vary the aspect ratio of the capillary. Both the cladding outer radius and the cladding thickness change during the redraw step by less than 20%.