Multi-mode Optical Fiber Chlorine Doping Profile
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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, which are challenging to mitigate with conventional GeO2 doping alone.
Innovation Solution
Controlled chlorine concentration profiles in the core of the multi-mode optical fiber are implemented to reduce residual stresses and maintain a stable refractive index profile, specifically by increasing chlorine concentration towards the outer periphery, thereby reducing glass viscosity differences and enhancing bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If GeO2 is added to the core to obtain the correct concentration in the diametric direction, then the refractive index profile can be improved, but residual stresses remain inside the optical fiber causing refractive index fluctuations
Solution Approach 1:
The patent changes the chemical composition parameters by introducing chlorine doping in addition to GeO2 doping. The chlorine concentration is specifically controlled to create a profile that compensates for stress-induced refractive index changes, thereby maintaining profile stability while achieving the desired refractive index distribution.
Solution Approach 2:
The patent creates a composite doped glass structure in the core by combining GeO2 and chlorine dopants. This composite doping approach allows the GeO2 to provide the primary refractive index increase while the chlorine dopant mitigates stress effects, resulting in a more stable overall refractive index profile.
2Duration of action of stationary object
If the optical fiber is cooled after drawing, then solidification occurs, but stresses remain inside the optical fiber due to differential cooling and expansion coefficients
Solution Approach 1:
The patent modifies the thermal and mechanical parameters during the drawing and cooling process by optimizing the drawing temperature, cooling rate, and tension applied to the preform. These parameter adjustments control the solidification process to minimize differential contraction between core and cladding, reducing residual stress generation.
Solution Approach 2:
The patent applies local quality control by creating a specific chlorine concentration profile within the core that is tailored to compensate for stress distribution. The chlorine concentration varies radially to match the stress profile, providing localized refractive index compensation where needed most during and after cooling.
3Productivity
If the core shrinks during fiber cooling due to higher expansion coefficient, then bandwidth is limited, but reducing shrinkage creates manufacturing challenges
Solution Approach 1:
The patent changes the material composition parameters by adding chlorine dopant with different thermal expansion characteristics. This modifies the overall thermal expansion behavior of the core, reducing the differential shrinkage between core and cladding during cooling, thereby minimizing bandwidth-limiting stress effects while maintaining manufacturability.
4Ease of operation
If multi-mode optical fiber structure is used, then connection is easier and network construction is simpler, but transmission loss is higher than single-mode fibers
Solution Approach 1:
The patent optimizes multiple parameters including core diameter (47.5-52.5 μm), numerical aperture (controlled via GeO2 concentration), and refractive index profile shape (α value 1.9-2.2). These parameter optimizations reduce modal dispersion and transmission loss while preserving the ease of connection inherent in multi-mode fiber structures.
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 broadband multi-mode optical fiber with improved stability and expanded communication bandwidth, meeting the standards of OM3 and OM4 specifications, as evidenced by increased bandwidth capabilities.
Implementation Method 1
the chlorine concentration profile in the core, in the diametric direction of the multi-mode optical fiber, has a shape such that the chlorine concentration at the second measurement position within a range at a distance of from 0.9 a to 1.0 a from the center of the core in the radial direction thereof is higher than the chlorine concentration at the first measurement position at a distance of a/2 from the center of the core
Implementation Method 2
a core doped with GeO2 (germanium dioxide) and extending along a predetermined axis
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
Implementation Method 4
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
Data Source
AI summary
The present invention relates to a multi-mode optical fiber having a structure enabling stable production and broadening of communication bandwidth as compared with the conventional structures. The multi-mode optical fiber has a core with a diameter 2a that is doped with GeO2 and chlorine. The chlorine concentration profile in the core along the diametric direction of the multi-mode optical fiber has a shape such that the chlorine concentration at a second measurement position within a range at a distance of from 0.9 a to 1.0 a from the center of the core in the radial direction thereof is higher than the chlorine concentration at a first measurement position at a distance of a/2 from the center of the core in the radial direction thereof.