Multimode Optical Fiber Graded-Index Profile for Extended Wavelength Bandwidth
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Solution Overview
Problem
Current multimode optical fibers fail to meet the high bit rate demands of next-generation 400GbE systems due to limited bandwidth over extended wavelength ranges, particularly at wavelengths other than the optimum wavelength, and are challenging to manufacture using existing deposition processes.
Innovation Solution
A multimode optical fiber design featuring a central core with a graded-index profile co-doped with fluorine and germanium, where the alpha parameter varies with radial distance, allowing for high co-doping levels and refractive index profiles close to pure silica, extending the operating window beyond 150nm with improved bandwidth performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a graded-index profile with a single optimum alpha value is used, then bandwidth is maximized at a particular wavelength, but bandwidth becomes significantly small at other wavelengths
Solution Approach 1:
The patent applies a dynamic alpha profile where the alpha parameter varies with radial distance from the fiber core center. This creates different alpha values at different radii, allowing the fiber to maintain optimized bandwidth performance across multiple wavelengths simultaneously rather than being optimized for a single wavelength only
Solution Approach 2:
The patent changes the alpha parameter from a fixed single value to a spatially varying parameter that depends on radial position. This parameter transformation enables the refractive index profile to provide optimal mode equalization for multiple wavelengths, extending the operational wavelength range while maintaining high bandwidth performance
2Adaptability or versatility
If dopants like Phosphorus or Fluorine are used to modify refractive index, then wavelength dependence of optimum alpha is reduced, but bandwidth is not high enough to meet demand of high bit rate for next generation systems
Solution Approach 1:
The patent applies different dopant concentrations at different radial positions within the core. By co-doping with germanium and fluorine at spatially varying concentrations, the refractive index profile achieves both extended wavelength range and high bandwidth performance, with each region of the core optimized for its specific radial position
Solution Approach 2:
The patent uses composite doping with both germanium and fluorine in the silica core. This combination of dopants allows simultaneous achievement of extended wavelength operation and high bandwidth, as each dopant contributes different properties that complement each other in the graded-index profile
3Ease of manufacture
If high co-doping levels of fluorine and germanium are used, then refractive index profiles close to pure silica are achieved and manufacturing is easier, but bandwidth performance must be maintained over extended wavelength range
Solution Approach 1:
The patent uses a varying alpha parameter profile combined with high co-doping levels to maintain both manufacturability and performance. The spatially varying alpha profile compensates for the simplified doping approach, ensuring optimal bandwidth performance across extended wavelengths while keeping the manufacturing process straightforward
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 design achieves overfilled launch bandwidth greater than 3500MHz.km and calculated effective modal bandwidth greater than 4700MHz.km over a continuous wavelength range of 150nm to 200nm, enhancing bandwidth performance across multiple wavelengths while being easier to manufacture.
Implementation Method 1
Multimode fibers are affected by intermodal dispersion, which results from the fact that, in a multimode fiber, for a particular wavelength, several optical modes propagate simultaneously along the fiber, carrying the same information, but travelling with different propagation velocities.
Implementation Method 2
the multimode optical fibers used in data communications generally comprise a core, generally doped with Germanium, and showing a refractive index that decreases progressively going from the center of the fiber to its junction with a cladding
Data Source
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AI summary
The invention concerns a multimode optical fiber, with a graded-index core co- doped with at least fluorine F and germanium GeO2 and a refractive index profile with at least two α-values. According to the invention, the concentration of fluorine F at the core center ([F]r=0) is between 0 and 3wt% and the concentration of fluorine F at the core outer radius ([F]r=a) is between 0.5wt% and 5.5wt%, with [F]r=a - [F]r= > 0.4wt%. For wavelengths comprised between 850nm and 1100nm, said multimode optical fiber has an overfilled launch bandwidth (OFL-BW) greater than 3500MHz.km and a calculated effective modal bandwidth (EMBc) greater than 4700MHz.km over a continuous operating wavelength range greater than 150nm.