Hexagonal Tube Stacking for Hollow Core Photonic Band Gap Fibers
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Solution Overview
Problem
The existing methods for fabricating hollow core photonic band gap fibers using silica glass face challenges with interstitial voids and lattice errors due to the use of circular tube stacking, which are exacerbated by the high vapor pressure of specialty glasses, leading to difficulties in achieving accurate periodicity and position of holes, and are not adaptable for high-power laser transmission.
Innovation Solution
The method involves forming specialty glass tubes with hexagonal or polygonal outer transverse shapes, stacking them to minimize voids, and inserting them into a jacket tube to create a hollow-core photonic band gap preform, which is then drawn into fibers, reducing interstitial voids and lattice errors, and allowing for higher power laser transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If circular tubes are stacked to form the structured region, then the fabrication process is simple, but interstitial voids are introduced between stacked tubes making fiberization difficult
Solution Approach 1:
The patent applies asymmetry by changing the tube cross-sectional shape from circular to hexagonal. This geometric change allows hexagonal tubes to pack together with minimal interstitial voids, eliminating the spacing problems inherent in circular tube stacking while maintaining fabrication simplicity.
Solution Approach 2:
The patent utilizes the geometric properties of hexagonal shapes, which have curved edges and flat faces that naturally interlock when stacked. This shape characteristic reduces the gaps between adjacent tubes compared to circular shapes, improving the precision of hole positioning and periodicity in the final fiber structure.
2Ease of operation
If common circular tube stacking is used, then the process is straightforward, but tube slippage during fiberization adversely affects hole positioning accuracy
Solution Approach 1:
The hexagonal cross-section provides asymmetric geometry with flat faces that interlock during stacking, preventing tube slippage during the fiberization process. This geometric constraint maintains the intended hole positions and periodicity throughout manufacturing operations.
Solution Approach 2:
The patent addresses the slippage problem by adding geometric constraints in the transverse dimension through hexagonal shaping. This dimensional modification prevents lateral movement of tubes during stacking and fiberization, ensuring accurate hole positioning without complicating the stacking operation.
3Adaptability or versatility
If specialty glasses with high vapor pressure are used, then design flexibility is improved, but interstitial voids cannot collapse during fiberization
Solution Approach 1:
By using hexagonal tubes instead of circular tubes, the patent minimizes interstitial void formation at the source. This geometric modification eliminates the need for void collapse during fiberization, enabling the use of specialty glasses with high vapor pressure that would otherwise be unsuitable for fiber fabrication.
Solution Approach 2:
The patent performs preliminary action by pre-shaping the tubes into hexagonal cross-sections before stacking. This pre-shaping minimizes interstitial voids in advance, preventing the void collapse problem that occurs with circular tubes and high vapor pressure specialty glasses during subsequent fiberization.
4Strength
If silica glass is used, then mechanical integrity is achieved, but high softening temperature limits adaptability to extrusion processes
Solution Approach 1:
The patent changes the material parameter (softening temperature) by selecting specialty glasses with lower softening points than silica. This parameter change enables adaptability to extrusion and other forming processes while maintaining sufficient mechanical integrity for fiber fabrication through the hexagonal tube stacking method.
Data Source
AI summary
The present invention is generally directed to a method of making a hollow-core photonic band gap preform from a specialty glass by pressing a specialty glass through a die to form a tube wherein the outer transverse shape of the tube is a hexagon, triangle, quadrilateral, or other polygon; stretching the tube to form a micro-tube with approximately the same outer transverse shape as the tube; stacking a plurality of micro-tubes into a bundle minimizing voids between adjacent micro-tubes and forming a central longitudinal void wherein the plurality of micro-tubes within the bundle comprise an inner structured region of the preform and the central void of the bundle comprises a hollow core in the preform; and inserting the bundle into a jacket tube. Also disclosed are the hollow-core photonic band gap preform and fiber formed by this method.