Depressed-Cladding Core Rod Production via Segmented VAD-MCVD Fusion
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Solution Overview
Problem
Traditional methods for producing optical fibers, such as the vapor axial deposition (VAD) method, struggle to achieve complex refractive index profiles due to fluorine diffusion and high temperature processes, limiting the production of optical fibers with deep depression profiles, which affects the quality and attenuation of the fibers.
Innovation Solution
A method and apparatus that combine a core rod produced by VAD or OVD with an inner cladding casing using MCVD, PCVD, or POD, involving a high-temperature heat source, gas purging, and etching to control the refractive index profile and prevent moisture and impurity contamination, resulting in a depressed-cladding core rod with a cladding-to-core diameter ratio less than 4.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional VAD method is used to produce core rod, then production efficiency is improved with continuous production capability, but manufacturing precision deteriorates due to inability to achieve deep refractive index depression
Solution Approach 1:
The core rod production process is segmented into two distinct stages: first producing a core layer rod with simple structure using VAD method, then adding an inner cladding layer with depressed refractive index through MCVD/PCVD/POD methods. This segmentation allows each stage to optimize for its specific function, achieving both continuous production capability and deep refractive index depression.
Solution Approach 2:
The core layer rod is produced in advance using VAD method with its continuous production advantage, then the inner cladding layer is added subsequently through preliminary deposition and sintering processes. This preliminary action of creating the core structure first enables the later precise control of refractive index profile without compromising production efficiency.
2Speed
If high temperature deposition is used to add outer cladding layer, then deposition speed is improved, but quality of core rod deteriorates due to moisture and impurity contamination
Solution Approach 1:
The core rod is produced and sealed in advance using VAD method with its inherent dehydration capabilities, creating a high-quality core structure before outer cladding deposition. This preliminary action protects the core rod from subsequent high temperature processing, preventing moisture and impurity contamination while allowing fast outer cladding deposition.
Solution Approach 2:
The inner cladding layer acts as an intermediary barrier between the core rod and the outer cladding layer. It protects the core rod from direct exposure to high temperature and contaminants during outer cladding deposition, while still allowing the deposition process to proceed at high speed.
3Reliability
If inner cladding layer thickness is increased to protect core rod quality, then core rod protection is improved, but device complexity increases due to larger outer diameter ratio
Solution Approach 1:
The refractive index difference between the inner cladding layer and core rod is optimized to provide adequate protection with minimal thickness. By controlling the depression depth and thickness parameters, the inner cladding layer achieves effective protection while maintaining a compact outer diameter ratio, avoiding excessive device complexity.
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 enables the production of optical fibers with deeply depressed or complex refractive index profiles, reducing attenuation to less than 0.33 dB/km at 1383 nm, suitable for long-distance transmission and reducing the need for optical amplifiers and repeaters, while maintaining low water peak levels.
Implementation Method 1
a high temperature heat source arranged on the outside of the inner cladding casing
Implementation Method 2
fusing the inner cladding casing and the core layer rod together
Implementation Method 3
an external gas pipe adapted to transport various kinds of gases to the hollow shaft of the core rod component
Implementation Method 4
transporting a second mixture gas comprising a purge gas and an etching gas to the core rod hollow shaft to etch the interface of the glass
Data Source
AI summary
A method for producing a depressed-cladding core rod of an ultra-low water peak optical fiber, the method including 1) producing a core rod component; 2) producing an inner cladding casing component; 3) disposing the core rod hollow shaft and the casing hollow shaft respectively in the glass lathe; 4) cutting off connections among a pressure controlling pipe, a scrubber, and a vacuum pump; 5) connecting the inner cladding casing to the core rod hollow shaft hermetically; 6) turning on the glass lathe; 7) transporting a first mixture gas to the core rod hollow shaft; 8) moving a high temperature heat source; 9) transporting a second mixture gas to the core rod hollow shaft; 10) transporting the first mixture gas to the core rod hollow shaft; 11) transporting the first mixture gas under certain conditions; and 12) controlling relevant parameters to fuse the inner cladding casing with the core layer rod.