Ever wondered how major submarine cables are laid down in the ocean?
Submarine cables are laid down by using specially modified ships (sometimes even purpose built ships) that carry the submarine cable on board and slowly lay it out on the seabed as per the charts/plans given by the cable operator. The ships can carry with them up to 2,000 kilometers length of cable.
The ships are commonly referred to as cable-layers or cable-ships.
The cables are specially constructed for submarine operations as they have to endure harsh conditions as well as pressure.
Cable Dissection
Here is what a typical 3-D Cross-sectional cut-out of a submarine cable looks like:
- Polyethylene
- “Mylar” tape
- Stranded metal (steel) wires
- Aluminum water barrier
- Polycarbonate
- Copper or aluminum tube
- Petroleum jelly
- Optical fibers
In real-life the cable would look like this:
Here is another look…
Submarine cable laying process starts from the Landing Station, where a long cable section is attached (connected) to the landing-point and then extended out to a few miles in the sea. This end is connected to the cable on the ship and then the ship starts its cable laying process (a simple representation of this process can be seen/read here: http://www.k-kcs.co.jp/en
This is how the cable approaching the landing station looks like:
Depending on the geography of where the cable is laid out, the cable coming in from the ocean to the landing station might be advertised or not. Most of the time, it is buried as much as it can be and warning signs are placed so as to inform everyone that a submarine cable is landing ashore. Most of the time cable consortium companies try to hide the cable as much as they can, so that only those who need to know, are informed of the exact route of the cable. This would include municipalities, port authorities and shipping companies.
The market for submarine cables is dominated by Europe (UK, Italy, France, Germany) and a bit by Japan. US is overall a small player when compared to the others, as US itself did not have much need to expand cables to other countries, as much as the other countries had a need to connect to the US.
The ships, which are specialized, are almost all owned by the submarine cable consortium or manufacturers. These ships are station at various points along where the cable extends to ensure that in the event of a cable-cut, the ships can set sail immediately for cable repairs.
A cable laying ship at port
Cable coiled up in the cargo-hold (the coiling of 100s of miles of cable in the cargo hold is a proces that can take between 3 to 4 weeks to complete.
Another submarine cable laying ship at port
The portion of the ship from where the cables are lowered into the sea
A cable laying ship at sea. Notice the cable being lowered onto the sea bed, on the right hand side (starboard) (white portion) at the rear end of the ship.
Here is a photograph of a repeater being launched into the sea (which is placed every 40-60 kilometers) to fix and strengthen the fiber-optic signal and to amplify it, etc.
A submarine cable diver, inspecting a submarine cable.
When cables are damaged, either divers or specialized small sized submersible submarines with cameras and lights are sent down to the seabed to investigate where the cuts are. Then either divers of with the use of the robotic arms of the submersible ring the two ends of the cable onto the surface, where they are re-spliced and joined again.
Different cable types (by Alcatel)
Two informative videos regarding submarine cables and the technology & infrastructure behind them are below:
Undersea Cable
NTT Submarine Network Video
References:
- Cable Ships
- Submarine Communications Cable
- Installation Method
- eMarine Services Cable Photographs
- Subcom – the only US company that does underwater (submarine) cables
- Aboard Alcatel undersea cable ship (photos)
A very informative article - Thank you for sharing it :)
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