Optical Fiber Glass Preform Sintering for Uniform Refractive Index
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Solution Overview
Problem
Existing methods for manufacturing optical fiber glass preforms result in fluctuating refractive index distributions and optical characteristics along the longitudinal direction, leading to inconsistent cutoff wavelengths and mode field diameters.
Innovation Solution
Control the surface temperature difference of the porous glass preform to 50°C or lower in the longitudinal direction before sintering, and maintain a stable temperature for at least 2.5 hours before starting the sintering process, while using a fluorine compound gas and controlling the Ge doping to ensure uniform refractive index distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the porous glass preform is sintered immediately after deposition without temperature equalization, then the production time is reduced, but the refractive index distribution becomes non-uniform and optical characteristics fluctuate
Solution Approach 1:
The patent applies preliminary action by requiring the porous glass preform to be temperature-equalized to 200°C or lower before sintering begins. This preliminary temperature control step ensures uniform thermal conditions throughout the preform, preventing refractive index fluctuations while maintaining efficient production timing.
2Speed
If the sintering temperature is increased to accelerate dehydration and vitrification, then the processing speed is improved, but the temperature distribution becomes non-uniform causing refractive index fluctuations
Solution Approach 1:
The patent implements periodic action through a two-stage sintering process: first performing dehydration treatment at 1000-1300°C in chlorine gas atmosphere, then performing transparent vitrification at 1400-1600°C in helium gas atmosphere. This staged approach allows controlled heating that maintains uniform temperature distribution while achieving complete dehydration and vitrification.
3Reliability
If Ge doping is increased to enhance the refractive index of the core, then the optical fiber performance is improved, but the refractive index distribution becomes non-uniform along the longitudinal direction
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Ge doping concentration and distribution during the vapor-phase axial deposition process. By optimizing the GeO2 precursor gas flow rate and deposition conditions, the patent achieves uniform Ge distribution along the longitudinal direction while maintaining the required refractive index for optimal optical fiber performance.
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
Achieves a stable refractive index distribution and reduced fluctuations in optical characteristics, resulting in consistent optical fiber performance.
Implementation Method 1
an inside of the vessel being heated with a heater installed on an outer periphery of the vessel to form a heating region
Implementation Method 2
the porous glass preform undergoes a process of performing dehydration treatment by heating at 1000 to 1300° C. in a chlorine gas atmosphere
Implementation Method 3
the porous glass preform undergoes a process of performing dehydration treatment by heating at 1000 to 1300° C. in a chlorine gas atmosphere, and is further heat-treated at 1400 to 1600° C. in a helium gas atmosphere, thereby obtaining a transparent optical fiber glass preform
Implementation Method 4
a raw material gas is put into the oxyhydrogen flame formed by the burner, glass fine particles are generated by a flame hydrolysis reaction, and the generated glass fine particles are deposited in an axial direction of the starting rod
Data Source
AI summary
Provided is a method for manufacturing an optical fiber glass preform in which a refractive index distribution is stable in a longitudinal direction of the glass preform. A method for manufacturing an optical fiber glass preform includes: depositing a porous glass preform by a vapor phase method; and sintering the porous glass preform in a heating region, when sintering the porous glass preform, the porous glass preform being inserted into a vessel of a sintering furnace, and an inside of the vessel being heated with a heater installed on an outer periphery of the vessel to form the heating region. The sintering is started after a surface temperature difference of the porous glass preform in a longitudinal direction is made 50° C. or lower.