Optical Fiber Preform Plasma Torch Reciprocation Control
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Solution Overview
Problem
Existing methods for manufacturing optical fiber preforms using a plasma torch result in varying relative refractive index differences along the longitudinal direction and a rough surface at the lower portion of the glass rod, leading to low yield and poor optical characteristics.
Innovation Solution
Adjusting the plasma power during the deposition process by setting it higher at the beginning of the downward movement of the glass rod than during the steady state, and varying the length of this initial power setting to ensure a smooth surface and consistent refractive index difference along the optical fiber preform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the glass rod is reciprocated in the plasma torch to deposit fluorine-doped glass fine particles, then a cladding layer with high relative refractive index difference can be formed, but the relative refractive index difference varies in the longitudinal direction and the surface becomes rough
Solution Approach 1:
The glass rod is reciprocated in the plasma torch, alternating between downward movement (deposition phase) and upward movement (suspending phase). This dynamic motion pattern ensures uniform heating and consistent relative refractive index difference along the longitudinal direction while maintaining high deposition efficiency through continuous cycling
Solution Approach 2:
The reciprocating motion creates periodic cycles of deposition and suspension. During downward movement, deposition occurs; during upward movement, the rod is suspended to allow uniform heat distribution. This periodic action eliminates longitudinal variation in refractive index difference and prevents surface roughness
2Manufacturing precision
If the plasma power is increased to improve surface smoothness, then the relative refractive index difference increases, but the temperature of the glass rod rises excessively
Solution Approach 1:
The reciprocating motion allows the glass rod to dynamically alternate between high-temperature exposure during downward movement and cooling during upward suspension. This enables surface smoothness improvement through controlled heating without excessive temperature accumulation
Solution Approach 2:
Different sections of the glass rod experience different thermal conditions at different times during reciprocation. The local heating is controlled and distributed uniformly along the rod length, allowing surface smoothness improvement without causing excessive overall temperature rise
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 approach stabilizes the relative refractive index difference along the optical fiber preform's longitudinal direction, reduces surface roughness, and significantly improves the yield of usable optical fiber preform material.
Implementation Method 1
a plasma torch such as a radio-frequency induction thermal plasma torch is structured by arranging a radio-frequency coil around a tube providing a gas channel and operated through application of a radio-frequency current to the coil to convert the gas in the tube into plasmas
Implementation Method 2
In the plasma flame 4, fluorine-doped glass fine particles are produced and deposited onto the surface of a glass rod 6
Implementation Method 3
directly depositing a transparent fluorine-doped silica glass around a pure silica glass rod with the use of a plasma flame
Data Source
AI summary
A method of manufacturing an optical fiber preform by depositing glass fine particles onto a surface of a glass rod while the glass rod is reciprocated relative to a plasma torch, including: moving the glass rod in a first direction relative to the plasma torch while the plasma torch is applied to the glass rod and supplied at least with a dopant material and a glass material to deposit the glass fine particles onto the surface of the glass rod, in such a manner that a plasma power is set higher during a first time interval starting from a beginning of the movement of the glass rod in the first direction than during a second time interval starting from an end of the first time interval; and moving the glass rod in a second direction relative to the plasma torch, where the second direction is opposite to the first direction.