Gel-Free ADSS Cable Using High-Modulus PP Tubes
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Solution Overview
Problem
Traditional all dielectric self-supporting (ADSS) fiber optic cables face deformation under high compression forces during installation and operation, particularly in long spans, due to the use of heavy gel fillings and materials like poly (butylene terephthalate) (PBT), which increases weight, installation time, and costs, while also requiring substantial reinforcement and complex handling.
Innovation Solution
The use of polypropylene (PP) buffer tubes with high elastic modulus and a water swellable yarn instead of gel filling, combined with a central tension rod and dual sets of aramid yarns for water blocking, reduces cable weight and deformation, allowing the cable to withstand compressive loads and span longer distances without gel-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gel filling is used in traditional ADSS cables to prevent buffer tube deformation, then the cables can resist crushing forces during installation, but the cable weight increases and installation time is extended due to messy gel removal requirements
Solution Approach 1:
The patent removes the gel filling from the buffer tubes entirely, replacing it with a dry powder water-blocking material. This extraction eliminates the messy gel removal process that previously extended installation time, while the buffer tube deformation resistance is maintained through the high crush resistance of the PBT tube material itself and the structural support from the central strength member and aramid yarns.
2Reliability
If gel filling is used in traditional ADSS cables to prevent buffer tube deformation, then the cables can resist crushing forces during installation, but cable weight increases substantially
Solution Approach 1:
The patent extracts the gel filling from the buffer tubes, eliminating its weight contribution to the cable. The buffer tube deformation resistance is maintained through the inherent high crush resistance of the PBT tube material and the structural support from the central strength member and aramid yarns, without the added weight of gel.
Solution Approach 2:
The patent changes the physical state of the water-blocking material from liquid/gel phase to solid powder phase. This parameter change eliminates the weight and volume associated with gel filling while maintaining water-blocking functionality, thereby reducing cable weight without compromising buffer tube protection.
3Reliability
If PBT buffer tubes with gel filling are used to prevent deformation, then crush resistance is achieved, but cable cost increases due to heavy materials and substantial reinforcement requirements
Solution Approach 1:
The patent removes the gel filling, eliminating material costs associated with gel production and installation. The crush resistance is maintained through the high-strength PBT tube material and the structural support system, reducing overall cable cost while maintaining reliability.
Solution Approach 2:
The patent changes the water-blocking material from gel to dry powder form, which reduces material costs, simplifies the manufacturing process, and eliminates the need for expensive gel application and removal equipment, thereby reducing cable cost while maintaining protective functions.
4Reliability
If traditional gel-filled ADSS cables are used for long span installation, then buffer tubes are protected from deformation, but handling complexity and installation difficulty increase
Solution Approach 1:
The patent extracts the gel filling from the buffer tubes, eliminating the messy handling and removal operations that complicated installation. The buffer tube protection is maintained through the high crush resistance of the PBT tube material and structural support, thereby simplifying installation operations while maintaining reliability.
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 solution results in a lighter, cost-effective ADSS cable that can span longer distances with reduced installation time and tension on support structures, while ensuring optical reliability and faster splicing processes, with a weight reduction of 16% and up to 80% less time needed for splicing compared to traditional gel-filled cables.
Implementation Method 1
a water absorbent material... A first set of water blocking yarns are arranged to fill voids between the buffer tubes
Data Source
AI summary
A long span ADSS fiber optic cable has an outer jacket, a central tension rod member, and gel-free buffer tubes stranded around the rod member. Each tube is made of a flexible material having a determined elastic modulus, and optical fibers are contained in each tube with a water absorbent material. Water blocking yarns fill voids between the buffer tubes and surround the tubes. An inner jacket envelops the tubes and the yarns, and additional yarns are provided between the inner and the outer cable jackets. The elastic modulus of the buffer tubes is sufficiently high so that the cable sustains a compressive load of at least 220 N/cm over ten minutes with not more than a 0.1 dB increase in attenuation in any fiber. The rod member and the yarns enable the cable to span a distance of approximately 500 to 1050 feet in a NESC Heavy Load district.