Optical Fiber Preform Diameter Uniformity via Inverted Sintering
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Solution Overview
Problem
The existing methods for manufacturing optical fiber preforms result in uneven diameters due to gravitational effects during sintering, leading to complications in the drawing process and difficulty in achieving uniformity, especially with larger diameters, as the unsintered portion at the top is exposed to higher temperatures, causing uneven extension and diameter variations.
Innovation Solution
The method involves reversing the conventional approach by starting the furnace extension from the unsintered portion of the base material ingot, which is positioned at the bottom, and controlling the heating temperature to prevent premature melting, ensuring uniform extension and diameter consistency across the length of the preform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the base material ingot is sintered with the unsintered portion at the top to prevent gravitational extension, then the diameter uniformity is improved, but the extension process becomes complicated and productivity decreases
Solution Approach 1:
The patent inverts the conventional sintering approach by positioning the unsintered portion at the bottom instead of the top. This inversion allows the sintered portion to be at the top, enabling gravitational force to assist the extension process rather than hinder it. The unsintered portion at the bottom serves as a support that gradually transforms into glass, preventing unwanted extension while maintaining manufacturing efficiency.
Solution Approach 2:
The patent applies preliminary action by pre-positioning the unsintered portion at the bottom before the extension process begins. This preliminary arrangement ensures that during extension, the unsintered portion remains at the bottom and provides structural support, preventing the diameter variation that would occur if the sintered portion were at the bottom and subject to gravitational extension.
2Manufacturing precision
If the base material ingot is extended with the unsintered portion at the top, then the sintered portion extends uniformly, but the unsintered portion melts prematurely causing diameter variation
Solution Approach 1:
The patent inverts the position of the unsintered portion from the top to the bottom. This inversion ensures that the unsintered portion, which has lower thermal stability, is positioned where it will not be exposed to the highest temperatures during extension. The sintered portion at the top can be heated to the required extension temperature without causing premature melting of the unsintered portion.
Solution Approach 2:
The patent applies local quality by creating a temperature gradient along the length of the base material ingot. The unsintered portion at the bottom is exposed to lower temperatures, while the sintered portion at the top is exposed to higher temperatures suitable for extension. This localized temperature control prevents premature melting of the unsintered portion while enabling uniform extension of the sintered portion.
3Productivity
If the base material ingot diameter is increased to 100mm or more for mass production, then the productivity is improved, but the gravitational force causes greater diameter variation
Solution Approach 1:
The patent inverts the position of the unsintered portion to the bottom, which is particularly beneficial for large-diameter base material ingots (100mm or more). This inversion ensures that the entire circumference of the large-diameter ingot is supported by the unsintered portion at the bottom, preventing gravitational extension and diameter variation that would be more pronounced in larger ingots.
Solution Approach 2:
The unsintered portion at the bottom acts as a counterweight or support structure that compensates for the gravitational force acting on the large-diameter base material ingot. By positioning the unsintered portion at the bottom, it provides structural support that counteracts the gravitational tendency to cause diameter variation, enabling mass production of large-diameter preforms with maintained precision.
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 effectively restricts the diameter variation at the extension end, resulting in a preform with a uniform diameter and improved yield, facilitating more efficient mass production of optical fiber preforms.
Implementation Method 1
the porous glass base material 6 undergoes a sintering process that involves sintering in a heating furnace 7 to change the porous glass base material 6 into transparent glass
Implementation Method 2
thermally extending a base material ingot made of synthetic quartz and controlling the change in the outer diameter of the preform
Implementation Method 3
the base material ingot after sintering, as described in the above Publication, has an outer diameter that differs along the longitude thereof due to the gravitational force exerted on the base material ingot during sintering
Data Source
AI summary
Provided is a method of manufacturing an optical fiber preform, comprising obtaining a base material ingot by sintering a porous glass base material at a high temperature to change the porous glass base material into glass while retaining an unsintered portion at one end thereof that is not completely changed to glass; and while relatively moving a heating means in a longitudinal direction of the base material ingot, applying a tensile force to a heated portion and beginning to extend the unsintered portion from one side to decrease a diameter of and extend the base material ingot.