Optical Fiber Preform Hydrogen Flow Control
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Solution Overview
Problem
The transition from hydrogen produced at normal temperature to hydrogen vaporized from liquid hydrogen in optical fiber base material manufacturing disrupts the drawing up speed and core diameter, leading to unstable refractive index distribution and increased defective products due to differences in hydrogen flow rates and isomer concentrations.
Innovation Solution
An optical fiber base material manufacturing method and apparatus that adjust the flow rates of silicon tetrachloride and hydrogen based on calculated differences in drawing up speed, using a mass flow controller for thermal capacity measurement, to maintain constant flow rates and account for changes in hydrogen origin from normal temperature or vaporized liquid hydrogen, ensuring stable deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen obtained by vaporizing liquid hydrogen is used instead of hydrogen produced at normal temperature, then hydrogen supply stability is improved, but drawing up speed fluctuates and core diameter narrows
Solution Approach 1:
The invention changes the parameter being controlled from drawing up speed to hydrogen flow rate. By detecting deviations in drawing up speed and translating them into corrective adjustments of hydrogen flow rate, the system compensates for the instability introduced by using vaporized liquid hydrogen, thereby maintaining core diameter stability while preserving the reliability benefits of this hydrogen source
Solution Approach 2:
The invention implements a feedback control mechanism where the actual drawing up speed is continuously detected and compared with the target speed. The deviation information is fed back to adjust the hydrogen flow rate, creating a closed-loop control system that automatically compensates for fluctuations caused by using vaporized liquid hydrogen
2Productivity
If drawing up speed is increased to maintain production efficiency, then productivity is improved, but refractive index distribution becomes unstable
Solution Approach 1:
The system continuously detects drawing up speed and uses this feedback to adjust hydrogen flow rate in real-time, allowing the system to maintain optimal deposition conditions even at higher productivity levels, thereby preventing refractive index distribution instability
Solution Approach 2:
By shifting the control parameter from drawing up speed to hydrogen flow rate, the system can maintain precise control over the deposition process even when operating at higher speeds, ensuring refractive index stability is preserved while improving productivity
3Measurement precision
If mass flow controller is used to control gas flow rate, then flow rate control precision is improved, but measurement accuracy decreases when hydrogen origin changes
Solution Approach 1:
The invention changes the controlled parameter from drawing up speed to hydrogen flow rate. This allows the mass flow controller to operate within its optimal measurement range for hydrogen gas, maintaining high measurement accuracy regardless of the hydrogen origin (normal temperature or vaporized liquid hydrogen)
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 maintains consistent hydrogen flow rates and refractive index distribution, reducing defective products and ensuring stable optical characteristics of the optical fiber base material, even when switching between hydrogen sources.
Implementation Method 1
using a mass flow controller for thermal capacity measurement
Implementation Method 2
silicon tetrachloride (SiCl4) is supplied to an oxyhydrogen flame resulting from burning of hydrogen and oxygen by a burner, to generate silicon dioxide (SiO2) by means of hydrolysis
Implementation Method 3
an oxyhydrogen flame resulting from burning of hydrogen and oxygen by a burner
Implementation Method 4
vaporizes it by raising its temperature, and supplies it to the equipment at the later stage
Data Source
AI summary
An optical fiber base material manufacturing method includes: supplying oxygen, hydrogen, and silicide to a core deposition burner; depositing silicon dioxide; adjusting a drawing up speed so that a deposition tip position remains at the same position in accordance with growth of a porous base material; calculating an average of the drawing up speed at each preset time interval; calculating a difference of the calculated average from a preset value of the drawing up speed; correcting a flow rate of silicon tetrachloride when the supplied hydrogen is hydrogen produced or stored at normal temperature, and correcting a flow rate of hydrogen when the supplied hydrogen is hydrogen obtained by vaporizing liquid hydrogen, where when correcting the flow rate of hydrogen, a flow rate of hydrogen supplied to a cladding deposition burner is also corrected in a ratio of before and after the correction of the flow rate of the hydrogen.