Optical Fiber Preform Burner Position for Dopant-Stable Index Profiles
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Solution Overview
Problem
Existing methods for producing large optical fiber preforms face challenges in achieving sufficient heating of the core soot body center, leading to insufficient removal of metallic impurities and OH groups, which increases transmission loss and affects the zero dispersion wavelength due to volatilization of dopant materials like germanium dioxide.
Innovation Solution
Adjusting the flow rate ratios of carrier and sealing gases with silicon tetrachloride, and optimizing the position of the core portion burner for deposition, setting rside/rcore to 0.745 or more, to enhance the refractive index distribution and minimize dopant volatilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the core soot body size is increased to produce larger optical fiber preforms, then the productivity and output capacity increase, but the heating uniformity deteriorates causing insufficient removal of impurities and OH groups from the center portion
Solution Approach 1:
The heating process is segmented into multiple stages with different temperature profiles. The heating is performed in steps: first heating to a lower temperature to remove impurities and OH groups, then heating to a higher temperature to convert the soot body into transparent glass. This segmented approach allows the center portion of large core soot bodies to be adequately heated without causing excessive volatilization of dopant materials.
Solution Approach 2:
The heating temperature and time parameters are optimized based on the core soot body size. For larger core soot bodies, the heating time is extended and the temperature profile is adjusted to ensure sufficient heat penetration to the center portion while controlling the volatilization of germanium dioxide and other dopant materials. This parameter optimization maintains both productivity and manufacturing precision.
2Reliability
If the heater setting temperature is increased to provide sufficient heating to the center portion, then the impurity removal improves, but the dopant materials like germanium dioxide volatilize causing deterioration of optical properties
Solution Approach 1:
The heating process performs preliminary removal of impurities and OH groups at a lower temperature before increasing the temperature for glass conversion. This preliminary action at controlled temperatures prevents excessive volatilization of dopant materials while still achieving sufficient impurity removal from the center portion of the core soot body.
Solution Approach 2:
The heating is performed periodically in stages rather than continuously at high temperature. The process alternates between heating phases and holding phases, allowing impurity removal while controlling the rate of dopant volatilization. This periodic heating pattern maintains reliability by ensuring thorough impurity removal while minimizing the harmful effect of dopant loss.
3Reliability
If the heating time is extended to ensure sufficient heating of the center portion, then the impurity removal improves, but the productivity decreases
Solution Approach 1:
The heating process is made dynamic by adjusting the temperature profile based on the core soot body size and composition. For larger core soot bodies, the heating time is extended with optimized temperature profiles, while for smaller bodies, the process is shortened. This dynamic adjustment maintains high productivity while ensuring reliable impurity removal for each specific case.
Solution Approach 2:
The heating parameters (temperature, time, atmosphere composition) are changed and optimized based on the specific requirements of each core soot body. By carefully controlling these parameters, the process achieves sufficient impurity removal in shorter times compared to conventional methods, thereby maintaining high productivity without compromising reliability.
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
Improves the zero dispersion wavelength and optical properties of the optical fiber by ensuring uniform heating and maintaining the refractive index difference, resulting in desirable optical fiber performance.
Implementation Method 1
Glass raw materials are supplied to each burner along with combustible gas for flame formation, and porous optical fiber glass preform is produced by depositing glass fine particles generated in the flame emanating from the burner.
Implementation Method 2
a core soot body is produced by depositing glass fine particles generated in the flame emanating from the burner
Implementation Method 3
The core soot body is heat-treated by a heater to remove impurities and make transparent glass. Here, impurities are removed by flowing a gas containing chlorine atoms into the atmosphere gas while heating the core soot body at a temperature of about 1000-1200° C.
Implementation Method 4
heating to about 1200° C. in a chlorine-containing gas atmosphere to remove water and OH groups (called dehydration) contained therein
Implementation Method 5
The optical fiber can be obtained by heating the optical fiber preform to about 2000° C. to soften it, and then stretching it to a narrow diameter (called wire drawing)
Data Source
AI summary
The present invention provides an optical fiber with improved optical properties such as zero dispersion wavelength by suppressing the volatilization of dopant materials such as germanium dioxide and optimizing the refractive index distribution by adjusting the setting position of the core portion burner for deposition in a larger optical fiber preform. An optical fiber preform includes a core portion with a relatively high refractive index and a clad portion with a relatively low refractive index, wherein a position having a value of 45% of a refractive index difference between a center of the core portion and the clad portion is a boundary rcore (mm) between the core portion and the clad portion; and when a radius position r at which a refractive index difference with the clad portion being a maximum value is rside (mm), rside/rcore is 0.745 to 1.