Optical Fiber Drawing Method Suppressing Hydrogen Diffusion
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Solution Overview
Problem
Existing methods for manufacturing optical fibers with low absorption loss due to OH groups at the 1380 nm wavelength band are costly and inefficient, as they require complex processes and increased production costs, and often result in higher absorption losses due to hydrogen diffusion during the drawing process.
Innovation Solution
A drawing method for bare optical fibers that involves melting and rapidly cooling the optical fiber preform to control the thermal dissociation of OH groups, with a temperature history that satisfies the relational expression T≦−0.01X+12, where T is the time period at 1800° C. or higher, and a thermal dissociation coefficient of hydrogen that satisfies Y≦−8×10−5X+0.06, to minimize hydrogen diffusion and absorption loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the optical fiber preform is heated and drawn at high temperature for an extended period to ensure complete melting and drawing, then the drawing process is more complete and uniform, but hydrogen diffusion increases causing higher absorption loss due to OH groups
Solution Approach 1:
The patent applies parameter changes by precisely controlling the time-temperature profile during drawing. Specifically, it limits the time period T at 1800°C or higher to satisfy T≤-0.01X+12, where X is the OH group concentration. This parameter optimization allows the preform to be sufficiently melted and drawn while minimizing thermal dissociation of OH groups into hydrogen, thus resolving the contradiction between drawing completeness and hydrogen diffusion prevention.
2Object-generated harmful factors
If conventional manufacturing methods are used to reduce absorption loss, then production cost increases and manufacturing complexity increases
Solution Approach 1:
The patent achieves cost reduction by optimizing the drawing parameters rather than adding complex preprocessing steps. By controlling the time-temperature relationship (T≤-0.01X+12) during the standard drawing process, it minimizes hydrogen diffusion without requiring additional dehydration equipment or complex multi-stage processes, thus maintaining ease of manufacture while reducing absorption loss.
Solution Approach 2:
The patent skips the conventional dehydration step by directly optimizing the drawing parameters. Instead of performing separate dehydration treatments before drawing, it rushes through the drawing process with precisely controlled time-temperature parameters that prevent hydrogen diffusion in the first place, thereby simplifying the manufacturing process and reducing costs.
3Reliability
If the time period at high temperature is extended to ensure complete preform melting, then drawing quality improves, but hydrogen diffusion increases causing higher absorption loss
Solution Approach 1:
The patent resolves this contradiction by changing the time-temperature parameters to an optimized relationship. Instead of using extended high-temperature heating, it applies a controlled time limit T≤-0.01X+12 at 1800°C or higher, which is sufficient for complete melting and high-quality drawing while minimizing the thermal dissociation of OH groups into hydrogen, thus maintaining drawing quality while preventing absorption loss.
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 method reduces manufacturing costs and time while achieving a lower absorption loss at 1380 nm without dehydrating the cladding layer, improving yield and maintaining a low loss wavelength band of 0.31 dB/km or less.
Implementation Method 1
melting an optical fiber preform using a heating device
Implementation Method 2
The lower end of the optical fiber preform 32 is heated to approximately 2000° C. at high temperature and is drawn
Implementation Method 3
it is forcibly cooled by supplying cooling gas, such as helium or nitrogen gas, using a cooling cylinder 35
Implementation Method 4
The bare optical fiber 33 drawn out to the outside of the annealing furnace 34 is cooled to a temperature suitable to the formation of a coating layer
Implementation Method 5
When hydrogen diffuses into an optical fiber, it causes increased absorption loss due to OH groups
Data Source
AI summary
A drawing method for a bare optical fiber, comprises the steps of: melting an optical fiber preform using a heating device and drawing the bare optical fiber; and naturally cooling down the bare optical fiber or forcibly cooling down the bare optical fiber by a cooling device after the heating and melting step, wherein a temperature history during the drawing the optical fiber preform to obtain the bare optical fiber in the heating device satisfies a relational expression: T≦−0.01X+12 where a time period when the heated and molten portion of the optical fiber preform heated and molten by the heating device reaches 1800° C. or higher is T (min) and a OH group concentration in a cladding layer of the optical fiber preform is X (wtppm).