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Topic Last Updated on 03-07-2024
Early Joys
Post on topic: Underwater Cables.
Contemporaries celebrated the event as epoch-making. The press on both sides of the Atlantic competed to express their enthusiasm, practically equating a few telegram messages to the discovery of a new continent. The celebration, however, turned out to be premature: cables that had been laid only after a third attempt broke down after a little more than a month.
Only 732 messages were sent via its copper wires. From the point of view of modern volumes of information transfer, this was but a speck of dust — but that was only the beginning! Even then, it was obvious that communication cables would soon be the “backbone” of the infrastructure of the coming epoch. And the future came so suddenly that today, installations of new cables, grandiose in their capacities, are taken for granted and don’t spark much public interest.
Brusa
The first cable establishing a direct connection between Virginia Beach and Rio de Janeiro offers the lowest latency available today. It was designed specifically to minimise risks in the event of natural disasters.
Underwater Cables | The Coming Tide
In February 2018, the Spanish company Telxius began data transmission along the Marea cable (from the Spanish marea, “tide”) — an underwater cables connecting Virginia Beach on the East Coast of the US with Sopelana, a town near Bilbao in Spain. Another cable? The total length of global underwater communication cables only recently reached 930,000 mi, and there are no more than 500 of them overall (excluding military cables). What is so interesting about this project, then? Well, for one, we can use it to understand the principles and logic behind the installation of undersea cables.
To some degree, this cable can be called a corporate project: it was started by Microsoft, who later partnered with Facebook and the giants of the telecommunications industry, AT&T, Sprint, and Telefónica (Spain). The total cost of the project was more than $15 billion. For a 4,100 mile-long cable, the price for each mile was over $3.6 million. For comparison, the cost of optical fibers for data transmission doesn’t exceed $16 per mile! So, what makes it so expensive? Well, the difference between glass fiber and a communications cable is similar to that of a spool of thread and an evening gown by a high-fashion designer.
UnderWater Cables | What’s Inside?
Underwater cables have few but extreme requirements: durability, full waterproofing (even at depths of 3 miles with pressures up to 500 atm), mechanical strength for installation and operation, and stable performance over its 25-year lifespan.
The cable’s interior consists of fiber-optic cables with a core and cladding of different refractive indices. A light pulse travels through the fiber, repeatedly reflecting off surfaces, experiencing total internal reflection due to the optically dense environment. This reduces signal transmission speed by 40% compared to vacuum speed.
Layers of Submarine Cable Protection
A cable’s primary expense stems from its layered protective design. The first defense against seawater is polyethylene, resistant to various marine elements. Despite its impermeability, water eventually breaches its tiny pores, met by a BoPET film, often reinforced with Kevlar fibers.
Additionally, stranded galvanized steel wires form the next layer, akin to chainmail, safeguarding against tears from anchors, trawls, and marine life, as well as potential sabotage.
Anatomy of Submarine Cables
Beneath the steel armor lies a layered composition including polyethylene-aluminum, polycarbonate, and a tube filled with water-repellent gel. Inside this gel, thin copper tubes house optical fibers.
These copper elements serve several functions: reinforcing the cable, shielding from interference, and conducting current for control nodes and repeaters. Repeater stations manage laser retransmission, error control, and are spaced about 60 miles apart, enabling fast and accurate damage localization.
FIBER-OPTIC Data Transmission Cables
Optical fiber is an optically transparent material, usually plastic, through which pulses of light (or information) travel. In this process, the effect of total internal reflection against the cable’s walls is used. This is why the signal doesn’t attenuate and maintains a high speed when transmitted over long distances.
Underwater Cables | A Ton per Yard
A transatlantic cable’s weight per yard can reach up to one ton, but usually, the only fragments that are encased in extreme protection are those laid down at coastal and shallow-water areas. At great depths, where the effects of human activity are not as significant, there is no point in increased protection; therefore, a lighter, water-resistant cable with a diameter of 1 in is laid there, instead.
Still, the total weight of a cable running thousands of miles long reaches a few thousand tons. For example, Marea totaled at 5,125 t! Transporting such a delicate and bulky load is obviously not a simple task. Construction workers took a radical approach to this problem: the Spanish company Sanjo, specializing in the manufacture of fine blanking parts, built a small plant in Virginia Beach. The cable was constructed from ready-made fragments into long, multi-mile lines, which were then transported onto cable-laying vessels straight from the factory. This decision helped avoid the damage that occurs over ground transportation.
marea
With a 4101-mi length and a 200Tbps capacity, this transatlantic cable has the lowest latency and the highest capacity available today.
