Hole Assisted Optical Fiber Reduces Rayleigh Scattering Loss
Solution Overview
Problem
Current hole-assisted fibers (HAFs) face challenges in reducing Rayleigh scattering loss and manufacturing efficiency due to the large number of air holes required, which increases the risk of impurities and unevenness, while photonic crystal fibers (PCFs) have high light exudation and processing difficulties.
Innovation Solution
A hybrid structure of HAF and PCF with a core and cladding having a uniform refractive index, air holes arranged in two layers in a hexagonal closest packing configuration, and a specific center-to-center spacing, reducing the number of air holes and Rayleigh scattering loss by maintaining a normalized Rayleigh scattering coefficient of 0.92 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of air holes is increased to achieve PCF structure, then light confinement is improved, but manufacturing complexity and loss increase due to impurities and unevenness
Solution Approach 1:
The invention extracts the essential function of light confinement from the complex PCF structure by retaining only a small number of strategically positioned air holes (1-6 holes) in the cladding, removing the need for large numbers of air holes while maintaining the core light confinement capability
Solution Approach 2:
The invention applies local quality by concentrating the air hole structure in specific regions of the cladding rather than distributing it uniformly throughout, creating localized refractive index modifications that achieve light confinement with minimal air holes
2Reliability
If the number of air holes is increased, then light confinement is improved, but manufacturing precision deteriorates due to gaps and position shifts
Solution Approach 1:
The invention removes the manufacturing complexity by extracting only the essential air holes needed for light confinement, reducing the count from 36+ in PCF to 1-6 holes, which eliminates gap formation and position shift issues associated with capillary bundling
Solution Approach 2:
Instead of creating light confinement through the absence of material (air holes) as in PCF, the invention uses a solid core with minimal air holes in the cladding, inverting the traditional approach and simplifying the manufacturing process
3Reliability
If GeO2 doping is used in the core, then refractive index difference is improved, but Rayleigh scattering loss increases
Solution Approach 1:
The invention changes the refractive index parameter by using alternative doping methods or core structure modifications that achieve the required refractive index difference without relying on GeO2, thereby reducing Rayleigh scattering loss while maintaining light confinement
4Reliability
If air hole structure is used for light confinement, then single mode operation is achieved, but transmission loss increases due to impurities at inner surface
Solution Approach 1:
The invention extracts only the essential air holes needed for single mode operation and light confinement, reducing the number from 36+ to 1-6 holes, which minimizes the total inner surface area where impurities and unevenness can cause transmission loss
Solution Approach 2:
The invention segments the air hole structure into a minimal set of strategically positioned holes that independently contribute to single mode operation, allowing each hole to be optimized for function while minimizing overall loss
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 hybrid structure reduces Rayleigh scattering loss and enhances manufacturability by decreasing the number of air holes, achieving low loss properties over a wide wavelength region and improving processing accuracy.
Implementation Method 1
confines light by a refractive index difference between a cladding portion formed with air holes and a core portion
Implementation Method 2
reducing the number of air holes and Rayleigh scattering loss by maintaining a normalized Rayleigh scattering coefficient of 0.92 or less
Data Source
AI summary
An object of the present invention is to provide an HAF having a structure in which the number of air holes is decreased to be smaller than that of a PCF and Rayleigh scattering loss may be more reduced than that in the existing HAF. The HAF according to the present invention includes a core portion having a uniform optical refractive index; a cladding portion having a uniform optical refractive index and surrounding the core portion; and a plurality of air holes arranged in two layers at positions configuring hexagonal closest packing excluding the core portion within the cladding portion along a longitudinal direction of the hole-assisted fiber, wherein a center-to-center spacing of the air holes is a sum of a radius Rin of an inscribed circle inscribed in the air holes in an inner layer and a radius d/2 of the air hole, and a radius “a” of the core portion and a relative refractive index difference Δ between the core portion and the cladding portion are present within a range where Rn, which is a ratio of a Rayleigh scattering coefficient Rsmf of a single mode optical fiber and an effective Rayleigh scattering coefficient Reff of the hole-assisted fiber, is equal to or less than 0.92.