Optical Fiber with Depressed Cladding for Low Bend Loss
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Solution Overview
Problem
Existing optical fibers face challenges in achieving low bend losses while maintaining low cable cutoff wavelength, particularly in applications with tight bend radii and physical stress, such as in access and FTTx networks.
Innovation Solution
The development of optical waveguide fibers with specific refractive index profiles, including a central core region, inner cladding region, and outer cladding region, where the refractive index differences between these regions are carefully managed to achieve low bend losses and controlled dispersion properties, utilizing a super-Gaussian profile and depressed cladding regions to reduce microbending losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If optical fiber is deployed in applications with tight bend radii and physical stress, then the fiber must have high bend resistance, but this induces bend losses in optical signals
Solution Approach 1:
The patent applies local quality by creating a depressed index cladding region with specific refractive index characteristics (Δ2) that is localized around the core region (Δ1). This localized structural modification with different optical properties reduces microbending losses and improves bend resistance without affecting the overall fiber transmission characteristics negatively.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the refractive index difference between the core region (Δ1) and the depressed index cladding region (Δ2), where the difference is specified to be between 0.002% and 0.05%. This parameter optimization enables the fiber to achieve both low bend losses and low cable cutoff wavelength simultaneously.
2Loss of energy
If the fiber design achieves low bend loss, then bend resistance is improved, but it becomes difficult to achieve low cable cutoff wavelength at the same time
Solution Approach 1:
The depressed index cladding region with refractive index Δ2 creates a localized optical property modification that reduces microbending losses. This local structural change with specific index difference (0.002%-0.05% relative to core) enables simultaneous achievement of low bend losses and controlled cable cutoff wavelength.
Solution Approach 2:
The fiber structure combines multiple regions with different refractive index characteristics: the core region (Δ1), the depressed index cladding region (Δ2), and the outer cladding region (Δ3). This composite structure with carefully managed index differences enables the fiber to meet both low bend loss and low cable cutoff wavelength requirements.
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
These fibers exhibit reduced attenuation, lower macro- and microbending losses, and improved dispersion management, enabling better signal transmission with reduced noise ratio and bend resistance, meeting stringent performance criteria like 0.19 dB/km at 1550 nm and 0.32 dB/km at 1310 nm.
Implementation Method 1
a central core region having outer radius r1 and refractive index Δ1, a cladding region comprising a first inner cladding region having an outer radius r2>8 microns and refractive index Δ2, and a second outer cladding region having refractive index Δ4, wherein Δ1>Δ4>Δ2
Implementation Method 2
optical waveguide fibers comprising a central core region having outer radius r1 and refractive index Δ1
Data Source
AI summary
An optical fiber having both low macrobend loss and low microbend loss. The fiber has a first inner cladding region having an outer radius r2>8 microns and refractive index Δ2 and a second outer cladding region surrounding the inner cladding region having refractive index Δ4, wherein Δ1>Δ4>Δ2. The difference between Δ4 and Δ2 is greater than 0.002 percent. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r1/r2 is greater or equal to 0.25.