High-Density Optical Cable Using Low-Diameter, Bend-Insensitive Fibers
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Solution Overview
Problem
Optical fiber cables with high fiber density experience significant bend losses due to dense packing and positional constraints, leading to increased stress and signal attenuation during bending.
Innovation Solution
A high fiber density optical fiber cable design with low bend loss is achieved by using low diameter, bend insensitive optical fibers and tightly packed buffer tubes with controlled positional constraints, allowing optical fibers to maintain low strain positions during bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If optical fibers are densely packed to increase fiber density, then cable capacity and space utilization are improved, but bend losses increase due to positional constraints and increased stress
Solution Approach 1:
The patent changes the physical parameters of the optical fiber by reducing the outer diameter from conventional sizes to approximately 125 microns or less, and by modifying the coating properties (softer primary coating with lower Young's modulus). These parameter changes allow the fiber to bend more easily without increasing stress, thus maintaining low bend loss while enabling higher fiber density packing.
Solution Approach 2:
The patent employs a composite coating structure consisting of a primary coating layer with specific polymer properties (softer, lower modulus) and a secondary coating layer. This composite material approach allows the fiber to combine the mechanical flexibility needed for bending with the protective properties required for signal integrity, resolving the contradiction between density and bend loss.
2Quantity of substance
If optical fibers are densely packed in rigid buffer tubes, then fiber density is improved, but cable diameter and material usage increase
Solution Approach 1:
By changing the outer diameter parameter of the optical fiber to smaller values (125 microns or less), the patent reduces the space required per fiber. This parameter change enables higher fiber density within the same cable volume, thereby reducing overall cable diameter and material usage while maintaining or improving fiber density.
3Quantity of substance
If conventional optical fibers are used in high density cables, then fiber density is improved, but signal attenuation increases during bending
Solution Approach 1:
The patent modifies key parameters of the optical fiber including reducing outer diameter to 125 microns or less, changing the coating material properties (softer primary coating with Young's modulus between 0.1-10 MPa), and adjusting the refractive index profile. These parameter changes reduce the fiber's sensitivity to bending-induced stress, thereby minimizing signal attenuation while enabling high fiber density.
Solution Approach 2:
The patent uses a composite coating system with a soft primary coating layer (low modulus) that can deform with bending stresses and a secondary coating layer for protection. This composite material structure allows the fiber to maintain signal integrity during bending in high-density cable configurations, reducing energy loss while achieving high fiber density.
Data Source
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AI summary
A optical cable is provided. The cable includes an outer cable jacket and a plurality of buffer tubes surrounded by the cable jacket. Each buffer tube includes an inner surface defining a channel having a diameter, D1, and an outer surface facing an inner surface of the cable jacket. The cable includes a plural number, N, of optical fibers, located within the channel of each buffer tube and surrounded by the inner surface of the buffer tube. Each optical fiber has an outer diameter, D2. The N optical fibers are densely packed within each buffer tube such that a diameter ratio parameter, Ω, is defined as the ratio D1/D2, and is 2.25+0.143(N) ≤ Ω ≤ 1.14+0.313(N).