Hollow Core Fiber Cable Lay Length for Bend Loss Reduction
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Solution Overview
Problem
Optical fiber cables with hollow core fibers (HCFs) face challenges in achieving a suitable minimum bend radius due to their increased stiffness, leading to issues with microbending and macrobending losses, especially during installation and long-term use, which affects transmission performance and life expectancy.
Innovation Solution
The design incorporates a specific lay length and lay angle for the cable elements, along with increased tension and cable modulus, to reduce strain on HCFs, ensuring a suitable minimum bend radius and improved flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hollow core fibers (HCFs) are used in optical fiber cables, then light transmission capability is improved, but fiber stiffness increases leading to larger minimum bend radius
Solution Approach 1:
The patent changes the lay length parameter from traditional values (typically 100-200mm) to extended values (300-500mm or more), which fundamentally alters the cable element geometry. This parameter change reduces the strain imposed on HCFs during bending, enabling the cable to achieve smaller minimum bend radii while maintaining transmission performance.
Solution Approach 2:
The patent introduces dynamic tension application during the lay process, where controlled tension is applied to cable elements as they are laid around the central strength member. This dynamic tension control allows optimization of the lay angle and packing density, improving cable flexibility without compromising HCF integrity.
2Ease of operation
If increased tension and cable modulus are applied to reduce strain on HCFs, then minimum bend radius is improved, but cable element lay length must be extended
Solution Approach 1:
The patent systematically changes multiple parameters including lay length (extending to 300-500mm), tension force (optimizing during lay process), and lay angle (adjusting based on cable construction) to achieve the optimal balance between bend radius and lay length. These coordinated parameter changes enable extended lay length to produce improved flexibility rather than being merely a compromise.
3Ease of manufacture
If traditional cable element lay length is used with HCFs, then manufacturing simplicity is maintained, but microbending and macrobending losses increase
Solution Approach 1:
The patent modifies the lay length parameter from traditional short values to extended values (300-500mm+), which changes the geometric relationship between cable elements and the central strength member. This parameter change reduces the curvature strain on HCFs, minimizing microbending and macrobending losses while maintaining manufacturability through standardized lay processes.
4Strength
If HCF diameter is increased to preserve mechanical integrity, then fiber strength is improved, but fiber stiffness increases reducing cable flexibility
Solution Approach 1:
The patent changes the lay length parameter to extended values (300-500mm or more), which compensates for the increased stiffness of larger diameter HCFs. By extending the lay length, the strain during cable bending is reduced, allowing larger diameter HCFs to be used while maintaining acceptable cable flexibility and small minimum bend radius.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
An optical fiber cable comprising a cable element. The cable element comprises a hollow core optical fiber (HCF). A lay length of the cable element is in a range of 325 mm to 500 mm, in a range of 375 mm to 450 mm, is approximately 400 mm, or is approximately 450 mm. Also, a method of manufacturing the optical fiber cable, and a method of transmitting information using the cable.