Optical Fiber Preform Two-Stage Cladding Low Water Peak
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Solution Overview
Problem
Optical fibers manufactured using traditional methods often exhibit a 'water peak' in attenuation spectra due to hydroxyl radical and water absorption, leading to increased linear attenuation at 1380 nm, which is not compliant with ITU-T recommendations for single-mode transmission.
Innovation Solution
A two-stage cladding process is employed, where an intermediate glass preform with a smaller core-to-clad ratio is formed, followed by completion of the cladding to produce an optical fiber preform, using a flame hydrolysis deposition process to minimize water contamination and achieve a low water peak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional single-stage cladding process is used, then manufacturing process is simple, but water peak attenuation is high (greater than 0.30 dB/km at 1380 nm)
Solution Approach 1:
The cladding process is divided into two distinct stages: first forming an intermediate glass preform with a first cladding layer, then completing the cladding to form the final optical fiber preform with a second cladding layer. This segmentation allows each stage to be optimized independently, with the first stage focusing on minimizing water peak attenuation and the second stage completing the structural requirements.
Solution Approach 2:
The intermediate glass preform is formed in advance with controlled composition and structure before the final cladding is applied. This preliminary action ensures that the core and first cladding are optimized for low water peak attenuation before the outer cladding is added, preventing water contamination at critical interfaces.
2Object-affected harmful factors
If intermediate glass preform formation is added, then water peak attenuation is reduced, but manufacturing time increases
Solution Approach 1:
The formation of the intermediate glass preform and the final optical fiber preform are merged into a continuous two-stage process where the intermediate preform serves as the foundation for the final product. This integration allows the intermediate structure to be reused and built upon, rather than creating separate discrete components.
Solution Approach 2:
The chemical composition parameters are changed between stages: the intermediate glass preform has a specific composition optimized for low water content, while the final preform adds outer cladding layers with different compositional requirements. This parameter optimization at each stage reduces water peak attenuation without requiring excessive processing time.
3Productivity
If core-to-clad ratio is increased for higher yield, then manufacturing efficiency improves, but water peak attenuation increases
Solution Approach 1:
Different regions of the optical fiber preform have different compositions optimized for their specific functions: the core and first cladding region has composition optimized for low water peak attenuation, while the outer cladding region has composition optimized for mechanical protection and optical confinement. This local quality optimization allows high core-to-clad ratio without compromising water peak 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
This method results in optical fibers with attenuation at 1383 nm of less than 0.30 dB/km, meeting the specifications for single-mode optical transmission systems and reducing manufacturing time while maintaining high throughput.
Implementation Method 1
A two-stage cladding process is employed, where an intermediate glass preform with a smaller core-to-clad ratio is formed, followed by completion of the cladding to produce an optical fiber preform, using a flame hydrolysis deposition process
Implementation Method 2
consolidating the soot intermediate preform to form a glass intermediate preform
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
A method of manufacturing at least one optical fibre preform comprising: providing a plurality of partially porous intermediate preforms, each partially porous intermediate preform having a longitudinal axis and comprising a respective soot intermediate clad layer formed around a respective glass core rod comprising a central core region of radius a and an inner clad region of radius b to define a first core-to-clad ratio a/b; consolidating the formed soot intermediate clad layers to form a respective plurality of intermediate glass preforms, each of the plurality of intermediate glass preforms comprising an intermediate clad region having an external radius c to define a second core-to-clad ratio a/c of from 0.20 to 0.30, and overcladding at least one intermediate glass preform by forming an overclad region surrounding the intermediate clad region to form an optical fibre glass preform, wherein consolidating comprises exposing the plurality of intermediate preforms to a consolidation hot zone of a single furnace body while rotating each of the intermediate preforms about its respective longitudinal axis.