Optical Fiber Preform with Alkali Metal and Oxygen Doping
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Solution Overview
Problem
Existing methods for manufacturing optical fibers with alkali-metal-doped core regions face challenges in achieving low attenuation and high production yield, with high concentrations of dissolved oxygen molecules often leading to increased attenuation and increased costs due to lengthy doping processes.
Innovation Solution
The development of an optical fiber preform composed of silica-based glass with an alkali-metal-doped core region, where the maximum concentration of oxygen molecules is 30 mol ppb or more and the average alkali metal concentration is 5 atomic ppm or more, along with a cladding portion doped with fluorine, using a method that includes alkali-metal-doping, oxygen-molecule-doping, and controlled collapsing of the glass pipe to optimize the core glass composition and reduce impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the concentration of oxygen molecules in the core portion is increased to enhance network structure relaxation, then the attenuation of the optical fiber is reduced, but the manufacturing cost increases due to lengthy doping processes
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration of oxygen molecules (30-100 mol ppb) and alkali metals (5-100 atomic ppm) in the core portion. By optimizing these chemical parameters, the patent achieves low attenuation while reducing the doping process time, as the specific concentration ranges enable effective network structure relaxation without requiring excessively long doping durations
Solution Approach 2:
The patent creates a composite doped glass structure by combining oxygen molecules and alkali metals in specific concentrations within the silica-based core portion. This composite doping approach allows the two dopants to work synergistically - oxygen molecules provide network structure relaxation while alkali metals contribute to viscosity reduction during drawing, achieving low attenuation more efficiently than single-dopant methods
2Stability of the object's composition
If the concentration of alkali metals in the core portion is increased to reduce viscosity during drawing, then the network structure relaxation is enhanced, but the attenuation increases due to impurity effects
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alkali metal concentration within 5-100 atomic ppm in the core portion. This optimized parameter range provides sufficient viscosity reduction during drawing to enable effective network structure relaxation, while remaining low enough to avoid excessive attenuation from impurity effects, thus resolving the contradiction between structural relaxation and attenuation
Solution Approach 2:
The patent applies local quality by creating a non-uniform distribution of alkali metals and oxygen molecules within the core portion. The core region contains these dopants at optimized concentrations to achieve local network structure relaxation and viscosity control, while the overall composition remains balanced to prevent excessive attenuation, allowing different regions to have tailored properties for their specific functions
3Manufacturing precision
If the glass pipe is heavily etched to remove transition metal impurities, then the purity of the core portion is improved, but the concentration of alkali metals is reduced due to simultaneous removal
Solution Approach 1:
The patent applies partial action by performing controlled etching that removes only a portion of the glass pipe wall - sufficient to eliminate transition metal impurities but limited enough to preserve the majority of doped alkali metals. Since alkali metals have higher diffusion rates and are more concentrated near the inner surface, a moderate etching depth selectively removes impurities while retaining the functional dopants, achieving purity improvement without excessive alkali metal loss
Solution Approach 2:
The patent applies feedback by monitoring and controlling the etching depth and duration to achieve the optimal balance between impurity removal and alkali metal retention. The etching process parameters are adjusted based on the desired final concentrations of both impurities and dopants, creating a feedback-controlled process that maintains alkali metal concentration within the target range (5-100 atomic ppm) while achieving the required purity level
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 results in optical fibers with attenuation as low as 0.165 dB/km at 1550 nm, improving transmission performance and reducing manufacturing costs by optimizing the concentration of alkali metals and oxygen molecules while maintaining a high yield.
Implementation Method 1
a glass pipe composed of silica-based glass is heated by an external heat source or non-equilibrium plasma is generated in the glass pipe while vapor of a raw material such as an alkali metal or an alkali metal salt is introduced into the glass pipe, thereby doping an inner surface of the glass pipe with an alkali metal element by diffusion
Implementation Method 2
an oxygen-molecule-doping step of doping the glass pipe with oxygen molecules by heating the glass pipe while supplying oxygen gas to the inside of the glass pipe
Implementation Method 3
After the glass pipe is doped with an alkali metal by the diffusion method, the glass pipe is heated to reduce the diameter thereof
Data Source
AI summary
An optical fiber preform includes a core portion, in which the core portion includes an alkali-metal-doped core glass portion doped with an alkali metal, the maximum concentration of oxygen molecules in the core portion is 30 mol ppb or more, and the average concentration of the alkali metal in the core portion is 5 atomic ppm or more. A method of manufacturing an optical fiber preform includes an alkali-metal-doping step of doping a pipe composed of silica-based glass with an alkali metal, an oxygen-molecule-doping step of doping the glass pipe with oxygen molecules, and a collapsing step of collapsing the glass pipe by heating the glass pipe, in which the optical fiber preform is manufactured.