Multimode Optical Fiber Dual Alpha Graded Index Profile
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current multimode optical fibers fail to meet the high bandwidth demands of next-generation 400 GbE systems due to wavelength-dependent intermodal dispersion, with existing solutions either being difficult to manufacture or not achieving OM4 performance over an extended wavelength range.
Innovation Solution
A multimode optical fiber design featuring a central core with a graded-index profile defined by a power equation with two alpha values, co-doped with fluorine and germanium, allowing for a refractive index profile close to pure silica, and an outer cladding with a depressed refractive index trench, which extends the operating window beyond 150 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a graded-index profile with a single alpha value is used to minimize modal dispersion at a particular wavelength, then bandwidth is improved at that wavelength, but bandwidth degrades significantly 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 optimize modal dispersion compensation across multiple wavelengths simultaneously rather than at a single wavelength, thereby extending the operational bandwidth range
Solution Approach 2:
The patent changes the alpha parameter from a constant value to a variable value that depends on radial position. This parameter transformation allows the refractive index profile to be optimized for multiple wavelengths by having different alpha characteristics at different core regions, resolving the contradiction between single-wavelength optimization and multi-wavelength performance
2Reliability
If the core refractive index is increased through doping to improve bandwidth, then manufacturing complexity increases due to precise dopant distribution requirements
Solution Approach 1:
The patent implements local quality by having the alpha parameter vary at different radial positions within the core. This allows different regions of the core to have optimized dopant concentrations and alpha values tailored to specific wavelength ranges, improving overall bandwidth performance while distributing the manufacturing precision requirements across different zones rather than requiring uniform precision throughout
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 fiber achieves overfilled launch bandwidth and effective modal bandwidth greater than 3500 MHz·km and 4700 MHz·km respectively over a continuous wavelength range of 150-200 nm, enhancing data transmission reliability and compatibility with various wavelengths.
Implementation Method 1
the central core has (i) an outer radius a, (ii) a transition radius rt that is less than the outer radius a, (iii) a maximum refractive index n0, (iv) a minimum refractive index nCl, and (v) a graded-index profile n(r) that is a function of the radial distance r from the center of said central core
Implementation Method 2
wherein said central core is co-doped with at least fluorine F and germanium GeO2
Data Source
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 3 wt % and the concentration of fluorine F at the core outer radius ([F]r=α) is between 0.5 wt % and 5.5 wt %, with [F]r=α−[F]r=0>0.4 wt %. For wavelengths comprised between 850 nm and 1100 nm, said multimode optical fiber has an overfilled launch bandwidth (OFL-BW) greater than 3500 MHz·km and a calculated effective modal bandwidth (EMBc) greater than 4700 MHz·km over a continuous operating wavelength range greater than 150 nm.