Truncated Core Optical Fiber Bend Loss
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Solution Overview
Problem
Optical fibers face significant bend loss issues due to curvature, particularly in multimode fibers where high order modes suffer greater loss than low order modes, limiting their bandwidth and signal carrying capacity.
Innovation Solution
The optical fiber design incorporates a truncated core with a steep vertical step and optional ledge, eliminating the need for a negative trench, allowing the core to function as both a light guiding structure and a trench, thereby maintaining good bend loss performance without negative refractive index regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative trench is used to control bend loss, then bend loss performance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention extracts and eliminates the negative trench component from the fiber structure. By removing this complex feature, the patent simplifies the overall fiber design while maintaining bend loss control through alternative means (optimized core diameter and refractive index profile), thereby resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent changes key parameters of the core structure, specifically optimizing the core diameter and refractive index profile. These parameter adjustments allow the core to perform dual functions (light guidance and bend loss control) without requiring a negative trench, thus improving reliability while reducing device complexity
2Reliability
If a negative trench is used to control bend loss, then bend loss performance is improved, but ease of manufacture decreases
Solution Approach 1:
The invention removes the negative trench feature from the manufacturing process. This extraction eliminates the need for complex doping and deposition steps required to create negative index regions, significantly improving ease of manufacture while maintaining bend loss performance through optimized core parameters
Solution Approach 2:
By changing the core parameters (diameter and refractive index profile) rather than adding a negative trench, the patent enables simpler manufacturing processes that do not require the complex fabrication steps needed for negative index regions, thus resolving the contradiction between reliability and ease of manufacture
3Ease of manufacture
If conventional graded index profile is used, then manufacturing is simple, but bend loss control is insufficient
Solution Approach 1:
The patent optimizes specific parameters of the graded index profile, particularly the core diameter and refractive index distribution. These parameter changes enhance bend loss control while maintaining the relative simplicity of manufacturing a positive index profile, resolving the contradiction between ease of manufacture and bend loss performance
Solution Approach 2:
The optimized core structure performs multiple functions simultaneously: it guides light and controls bend loss. This multi-functionality eliminates the need for separate trench structures, maintaining manufacturing simplicity while improving bend loss performance
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 enhances bend loss performance, simplifies fabrication, and maintains exceptional signal integrity over various bending diameters and distances, meeting or exceeding industry standards for bandwidth and bit error rate, especially when used with VCSEL sources.
Implementation Method 1
light follows a straight path but can be guided to some extent by providing a path, even a curved path, of high refractive index material surrounded by material of lower refractive index
Implementation Method 2
a graded index core with an alpha profile inner portion and a steep vertical step between the core and the cladding
Data Source
AI summary
Optical fiber designs are depicted with a core having an alpha profile inner portion and a steep vertical step between the core and a cladding with no shoulder, referred to herein as a truncated core. A further aspect of this invention can include a trench between the truncated core and cladding. In this embodiment, the core performs as not only as the primary light guiding structure, but now also functions essentially the same as that of a trench structure. Thus, what was formally a trench can now be much less negative or even positive. Another embodiment of the present invention includes an optical fiber having a truncated core with the addition of a ledge or shoulder between the core and vertical step, followed directly by a cladding.