Co-doped Optical Fiber with Graded Refractive Index Core
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Solution Overview
Problem
Current optical fibers face limitations in low attenuation and high fiber nonlinearity, particularly in high-speed, long-haul transmission applications, due to micro- and macro-bending losses and Rayleigh scattering, which are not adequately addressed by existing designs.
Innovation Solution
A single mode optical fiber with a graded refractive index core co-doped with fluorine and chlorine, featuring a non-uniform concentration profile and a depressed cladding region, which reduces attenuation to less than 0.17 dB/km at 1550 nm by minimizing Rayleigh scattering and viscosity fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the effective area of the fiber is increased to reduce fiber nonlinearity, then power density decreases and nonlinearity is reduced, but micro- and macro-bending losses increase
Solution Approach 1:
The patent applies local quality by creating a graded refractive index profile within the core where the refractive index varies continuously from the center to the edge. This gradual variation in optical properties allows the fiber to maintain higher effective area for reduced nonlinearity while the graded profile confines the mode more effectively, reducing sensitivity to bending losses. The dopant concentrations (alumina, phosphorus pentoxide, boron trioxide) are distributed non-uniformly to achieve this graded profile.
Solution Approach 2:
The patent changes the refractive index parameter by introducing multiple dopants with different concentrations at different radial positions in the core. The refractive index is modified according to the formula n = n0 + Δn, where Δn depends on the local dopant concentrations. This parameter change enables the fiber to achieve the desired balance between effective area and bending loss by carefully controlling how the refractive index varies across the core cross-section.
2Loss of energy
If conventional doping methods are used to achieve low attenuation, then manufacturing is simpler, but attenuation cannot reach below 0.17 dB/km at 1550 nm
Solution Approach 1:
The patent uses composite materials by combining multiple dopants (alumina, phosphorus pentoxide, boron trioxide) within the silica core to achieve the desired optical properties. Each dopant contributes differently to the refractive index and attenuation characteristics. The composite dopant system allows fine-tuning of the attenuation profile to achieve below 0.17 dB/km at 1550 nm while managing the complexity through synergistic interactions between the dopants.
Solution Approach 2:
The patent applies local quality by creating a graded refractive index profile within the core where the refractive index varies continuously from the center to the edge. This gradual variation in optical properties allows the fiber to maintain higher effective area for reduced nonlinearity while the graded profile confines the mode more effectively, reducing sensitivity to bending losses. The dopant concentrations (alumina, phosphorus pentoxide, boron trioxide) are distributed non-uniformly to achieve this graded profile.
3Speed
If single mode operation is maintained with conventional designs, then bandwidth is preserved, but effective area is limited and bending losses increase
Solution Approach 1:
The patent changes the refractive index parameter by introducing multiple dopants with different concentrations at different radial positions in the core. The refractive index is modified according to the formula n = n0 + Δn, where Δn depends on the local dopant concentrations. This parameter change enables the fiber to achieve the desired balance between effective area and bending loss by carefully controlling how the refractive index varies across the core cross-section.
Solution Approach 2:
The patent applies local quality by creating a graded refractive index profile within the core where the refractive index varies continuously from the center to the edge. This gradual variation in optical properties allows the fiber to maintain higher effective area for reduced nonlinearity while the graded profile confines the mode more effectively, reducing sensitivity to bending losses. The dopant concentrations (alumina, phosphorus pentoxide, boron trioxide) are distributed non-uniformly to achieve this graded profile.
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
The co-doped fiber design achieves low attenuation levels of less than 0.17 dB/km at 1550 nm, reducing fiber nonlinearity and manufacturing costs while maintaining compliance with G.652 and G.654 optical fiber standards.
Implementation Method 1
Multiple mechanisms can contribute to the attenuation and loss characteristics in optical fibers. These mechanisms can include Rayleigh scattering
Data Source
AI summary
A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a cladding in the fiber that surrounds the core addition, the core includes silica that is co-doped with two or more halogens.