Multimode Optical Fiber Wavelength-Independent Bandwidth Design
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Solution Overview
Problem
Conventional multimode optical fibers (MMFs) experience increased inter-modal dispersion and reduced transmission bandwidth when used with light sources operating at wavelengths other than 850-nm, leading to suboptimal performance in WDM transmission systems, particularly in achieving desired transmission characteristics such as chromatic dispersion and transmission loss.
Innovation Solution
The MMF structure is designed with a core and cladding that adjusts the doping amount of refractive index control agents to maintain an OFL bandwidth of at least 1500 MHz·km across 850-nm to 1300-nm wavelengths, reducing transmission loss to no more than 4.0 dB/km, allowing for relaxation of wavelength dependence and compatibility with 980-nm, 1060-nm, and 1300-nm light sources without the need for new fiber optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MMFs are designed for 850-nm VCSEL with small inter-modal dispersion, then transmission bandwidth at 850-nm is improved, but inter-modal dispersion increases and transmission bandwidth narrows when used with 980-nm, 1060-nm, or 1300-nm light sources
Solution Approach 1:
The patent applies parameter changes by adjusting the refractive index profile parameters (alpha value and maximum relative refractive index difference) to achieve wavelength-independent performance. Specifically, by optimizing these parameters, the fiber maintains small inter-modal dispersion across multiple wavelengths (850-nm, 980-nm, 1060-nm, and 1300-nm), resolving the contradiction between 850-nm optimization and multi-wavelength adaptability
Solution Approach 2:
The patent achieves universality by designing an MMF that can simultaneously support multiple light source wavelengths (850-nm, 980-nm, 1060-nm, and 1300-nm) with consistent transmission characteristics. This multi-functional design allows a single fiber type to replace multiple wavelength-optimized fibers, enabling future-proof transmission systems
2Manufacturing precision
If GI refractive index profile with alpha-power profile is used to suppress inter-modal dispersion, then transmission bandwidth is improved, but wavelength dependence of transmission characteristics increases
Solution Approach 1:
The patent resolves this contradiction by carefully selecting and optimizing the alpha value and maximum relative refractive index difference parameters of the GI refractive index profile. This optimization reduces the wavelength dependence of transmission characteristics while maintaining effective inter-modal dispersion suppression across the 850-nm to 1300-nm range
Solution Approach 2:
The patent applies local quality by creating a specific refractive index distribution profile where the core has a graded index structure with optimized alpha value. This localized optimization in the core region achieves wavelength-independent performance while maintaining the overall fiber structure integrity
3Manufacturing precision
If cladding material is changed or core is doped with multiple kinds of elements to adjust refractive index, then transmission loss increases and chromatic dispersion degrades
Solution Approach 1:
The patent resolves this contradiction by optimizing the doping concentration and type in the core region to achieve the desired refractive index profile. By carefully controlling the alpha value and maximum relative refractive index difference through precise doping, the fiber achieves good transmission loss characteristics (around 3.0-4.0 dB/km at 850-nm) while maintaining chromatic dispersion within acceptable ranges
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 design enables upgrades to existing transmission systems, ensuring sufficient transmission characteristics for WDM systems by maintaining wide OFL bandwidth and minimizing chromatic dispersion, thus supporting faster transmission speeds without replacing conventional MMFs.
Implementation Method 1
a refractive index profile in which a doping amount of a dopant for control of refractive index... is adjusted
Implementation Method 2
core extending along a predetermined axis, and cladding provided on an outer peripheral surface of the core
Implementation Method 3
the core is provided with the refractive index profile called an α-power profile, for suppressing the inter-modal dispersion
Implementation Method 4
Multimode optical fiber... transmission bandwidth in the 850-nm transmission wavelength band is defined as a standard
Data Source
AI summary
The present invention relates to an MMF with a structure for relaxing wavelength dependence of transmission bandwidth. In the MMF, a doping amount of a dopant for control of refractive index is adjusted, so as to make each of an OFL bandwidth at a wavelength of 850 nm and an OFL bandwidth at a wavelength of at least one of 980 nm, 1060 nm, and 1300 nm become not less than 1500 MHz·km, make the OFL bandwidth at the wavelength of at least one of 980 nm, 1060 nm, and 1300 nm become wider than the OFL bandwidth at the wavelength of 850 nm, and effectively suppress increase in transmission loss.