Multi-mode Optical Fiber Chlorine Doping Residual Stress
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Solution Overview
Problem
Multi-mode optical fibers experience higher transmission loss and limited communication bandwidth due to residual stresses and refractive index fluctuations caused by differences in glass solidification temperatures between the core and cladding, which are exacerbated by the higher expansion coefficient of the core material GeO2.
Innovation Solution
Control the chlorine concentration profile along the diametric direction of the multi-mode optical fiber to bring the glass solidification timings closer together, reducing residual stresses and maintaining a stable refractive index profile by doping both the core and cladding with chlorine, with a higher average concentration in the cladding than in the core, thereby reducing the viscosity difference and minimizing refractive index changes during the cooling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If GeO2 is added to the core to achieve the correct refractive index concentration, then the refractive index profile can be obtained, but residual stresses remain due to the higher expansion coefficient of the core causing significant shrinking during fiber cooling
Solution Approach 1:
The invention applies different chlorine concentrations to different regions of the optical fiber. The cladding region receives a higher chlorine concentration than the core region, creating a localized chemical modification that equalizes solidification timing between core and cladding without altering the core's GeO2-based refractive index profile
Solution Approach 2:
The invention changes the chemical composition parameter by introducing chlorine doping with a specific concentration gradient. The chlorine concentration in the cladding is set higher than in the core, which modifies the solidification characteristics of the cladding to match the core's solidification timing, thereby reducing thermal stress during cooling
2Stability of the object's composition
If the core shrinks significantly during fiber cooling due to higher expansion coefficient, then the refractive index profile varies under residual stresses, but reducing residual stresses to zero is difficult
Solution Approach 1:
The invention applies preliminary anti-action by pre-modifying the cladding's chemical composition with higher chlorine concentration before the cooling process. This pre-modification counteracts the tendency of the cladding to solidify at a different rate than the core, preventing the development of residual stresses that would otherwise cause refractive index profile variations
3Manufacturing precision
If different solidification conditions are applied to achieve desired refractive index profile, then manufacturing complexity increases, but uniform solidification is difficult to achieve
Solution Approach 1:
The invention simplifies the solidification control by changing the chemical composition parameter (chlorine concentration) rather than implementing complex thermal control mechanisms. By doping the cladding with higher chlorine concentration, the solidification timing is chemically adjusted to match the core's solidification rate, achieving uniform solidification under standard cooling conditions
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 a multi-mode optical fiber with improved stability and broader communication bandwidth, specifically meeting the standards for OM3 and OM4 fibers as defined by ISO/IEC 11801, with reduced residual stresses and minimal refractive index changes, enhancing signal quality and transmission efficiency.
Implementation Method 1
the cladding is doped with chlorine such that the average chlorine concentration in the cladding becomes higher than an average chlorine concentration in the core... the difference in glass solidification temperatures between the core and the cladding after drawing a preform can be made small
Implementation Method 2
since GeO2 has been added to the core and the expansion coefficient of the core is higher than that of the cladding, the core shrinks significantly during fiber cooling and stresses caused by such shrinking also remain in the obtained optical fibers
Implementation Method 3
when the optical fiber is cooled after drawing, the optical fiber temperature decreases from the surface of the optical fiber toward the interior thereof, and glass serving as a fiber material solidifies as the fiber cooling process proceeds
Data Source
AI summary
The present invention relates to a multi-mode optical fiber having a structure which can be produced with good stability with a communication bandwidth broader than that in the conventional structures, and in which both GeO2 and chlorine are added to a core thereof, and chlorine is also added to a cladding thereof. The cladding contains chlorine such that the average chlorine concentration therein becomes higher than the average chlorine concentration in the core.