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FEATURE CABLES & CONNECTORS
Designing a cable capable of
withstanDing a 5000n crush loaD
A group of engineers have came up with a
cable design that can withstand the highest of pressures, even
that of a direct spade strike. Here, STL looks into its design
installed in the outside of the cable jacket to provide a ruggedised ARP armoured cable, with very high tensile strength for overhead installation, and very high impact and crush resistance for underground installation. These cables can therefore be used as:
Worksafe Aerial cable – The consequences of aerial cable breakage can be fatal. STL’s product designers have developed one of a kind predictive braking capability in the product with embedded strength members engineered so that it breaks below a particular force, thus ensuring human safety. The micro design of the cable enables ultra-compact fibre packing, hence reducing the overall cable diameter. This enables easier handling and faster installation. In addition, this round cable can also be quickly and easily stripped, resulting in faster network rollouts. Direct bury underground cables – ~28%
of the service provider’s installations are underground and built currently using a duct. These cables are being designed keeping in mind their underground requirement.
installation
A spade test on the cable found that it was still optically
operational (with no fibre break) even after a direct spade strike
W
hile trying to establish Gigabit networks in the UK, one of the largest service providers in the region realised the
mounting pressure of meeting the 2025 deadline of full gigabit connectivity. Modelling to the Infrastructure Transition Research Consortium (ITRC) projects, the UK population will be 75 million by 2050 – and this 12.5% increase in population will further compound the need for faster connections with greater capacity. Deploying FTTx typically involves digging a
trench in the road or footpath to install ducting – and this can be very disruptive. In addition, in places where there are cobbled streets, for example, it can be costly and time and labour- intensive to take this approach. As well as wanting to limit the time spent on
site, the service engineers wanted a cable that was strong enough to withstand any weather conditions (maximum breaking force ~2000 Newton), and still be very flexible so that it could be bent for any type of deployment, be it aerial or underground. The high tensile strength of a fibre decides how much it is
3 DESIGN SOLUTIONS MARCH 2023 8
prone to breakage or can withstand a crushing load. It is generally measured in Newton (N).
arp cables
Most underground cables require additional materials (i.e. duct and joints) to protect the cable underground and cover connections or break-out points. However, new-generation designs can go straight into the ground. The idea: STL’s Armored Reinforced Plastic
(ARP) Drop Light Cables. ARP rods are non- metallic composites designed primarily for use as a central strength member in fibre optic cables. There are rugged, tightly buffered fibres reinforced with aramid yarns and sheathed with UV, chemical and abrasion-resistant polyurethane (TPU). The cable features a core made of Fibre Reinforced Plastic (FRP) that provided tensile strength and anti-buckling properties. Water swellable yarns were also added to prevent the entry of water at the core of the cable. ARP rods offer high tensile strength & better-bending properties with minimum weight. In this design, these same ARP rods were
Installing a cable underground usually involves two steps: installation of duct; and pulling up the cable. STL’s cable converts this into a single step as the cable allows direct bury installation without the need for duct installation, resulting in significant time and cost savings. This underground drop cable has very high
impact and crush strength and can withstand crush load till 5000 Newton, which is due to the bulletproof aramid yarn used in the 3 x ARP (Aramid-Reinforced Plastic). In fact a spade test on the cable found that it was still optically operational (with no fibre break) even after a direct spade strike, with signal loss well below the 1db limit, showing that it is remarkably robust. In addition, with the bend neutrality of the
3 x 120-degree embedded strength members, this cable excels in handling performance which offering strength, flexibility and the ability to break smartly. In Australia, customers asked for rural connectivity solutions where they actually do end-to-end underground cable installations, directly buried without any ducts. When they used this cable, designed for aerial use, for a direct bury environment, the cable is said to have worked brilliantly.
STL
www.stl.tech/
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