Optical Fiber Bending Loss Reduction via Depressed Cladding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical fibers face challenges in reducing bending loss without increasing connection loss and simplifying manufacturing processes, as methods like increasing core refractive index or forming holes complicate manufacturing and may increase connection loss.
Innovation Solution
An optical fiber design with a specific refractive index profile for the core and cladding layers, where the refractive index of the core, inner cladding, and outer cladding have defined relationships, allowing for reduced bending loss without decreasing the mode field diameter, and can be manufactured using existing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the refractive index of the core is increased to reduce bending loss, then bending loss is reduced, but mode field diameter decreases and connection loss with SSMF increases
Solution Approach 1:
The patent applies local quality by creating a depressed refractive index region specifically in the inner cladding layer adjacent to the core, while maintaining the core refractive index at standard levels. This localized modification of the refractive index profile allows the optical field to be confined more effectively during bending without requiring an increased core refractive index, thereby reducing bending loss while preserving mode field diameter and minimizing connection loss with SSMF.
2Loss of energy
If a trench-shape refractive index profile is adopted to reduce bending loss, then bending loss is reduced, but manufacturing complexity increases due to multiple layers with different refractive indices
Solution Approach 1:
The patent extracts the essential function of the trench structure (light confinement during bending) and implements it through a simplified depressed refractive index region in the inner cladding layer. Instead of creating a full trench-shape profile with multiple distinct layers and sharp boundaries, the invention uses a more gradual and simplified depressed region that achieves similar bending loss reduction while being easier to manufacture with existing preform fabrication techniques.
3Loss of energy
If holes are formed in the cladding to improve light containment, then bending loss is reduced, but manufacturing complexity and material costs increase
Solution Approach 1:
The patent changes the refractive index parameter in the inner cladding layer (creating a depressed region) to achieve light containment during bending, replacing the need for physical holes in the cladding. This parameter-based solution modifies the optical properties of the material itself rather than introducing structural complexities like holes, thereby achieving bending loss reduction through a simpler manufacturing process that uses standard preform fabrication methods without requiring additional hole-forming steps.
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 optical fiber achieves reduced bending loss and suppressed connection loss when wound around a mandrel, while maintaining a large mode field diameter and adhering to ITU-T recommendations, with a simplified manufacturing process and reduced material costs.
Implementation Method 1
an optical fiber has attracted attention in which an excessive loss, so-called bending loss (a macro bend loss) which occurs at the time of imparting bending properties, is reduced
Implementation Method 2
a refractive index of the core, an outer circumference radius r1 of the core, an outer circumferential radius r2 of the inner cladding layer
Data Source
AI summary
An optical fiber including a core and a cladding including an inner cladding layer and an outer cladding layer is provided. The refractive index of the core Δ1, the refractive index of the inner cladding layer Δ2, and the refractive index of the outer cladding layer Δ3 have a relationship denoted by the following expressions: Δ1max>Δ2min and Δ1max>Δ3, and 0.01%<|Δ2min−Δ3|<0.03%. An outer circumference radius r1 of the core, an outer circumferential radius r2 of the inner cladding layer, and an outer circumferential radius r3 of the outer cladding layer have a relationship denoted by the following expressions: r1<r2<r3, and 0.2≦r1/r2≦0.5. A cable cut-off wavelength λcc 1260 nm or less. A mode field diameter at a wavelength of 1310 nm is 8.6 μm or more and 9.5 μm or less.