Secrets of Submarine Cables - Transmitting 99 percent of all international data!
"Submarine cables support the Internet that we usually use. In the first part of the program, we learned that they can transmit tremendous amounts of data. In the second part, we will hear about how a submarine cable is laid down on the deep ocean floor."
Erika is an system engineer who came from Brazil to join NEC's submarine cable team. As a submarine cable expert, she designs and proposes submarine cables that are best suited to the needs and purposes of customers, mainly telecommunications carriers.
- MitaMs. Koga, we're happy to have you back on our program. First of all, how deep are submarine cables laid?
- KogaLet me see. They are laid down at different depths. For example, the deepest part of the submarine cable between Japan and the U.S. is about 8,000 meters below sea level (in the Japan Trench).
- Mita8,000 meters... That's a bit hard to imagine.
- KogaMt. Everest is over 8,000 meters high, so the depth is almost equal to that.
- MitaReally? The submarine cables are laid down in a deep place like that? Unbelievable! Then, it must be very difficult to lay submarine cables in the ocean.
- KogaYes. It is very difficult. The ocean floor has tall mountains (seamounts), deep valleys, soft muddy areas and hard rugged areas. We need to be careful and make sure that the submarine cable runs on a flat sea bed as much as possible while passing around sunken ships and other obstacles. That's why the preliminary exploration we conduct to decide the route of the submarine cable is very important. We spend a lot of time on the preliminary exploration and carefully decide on the route. But, while exploring these deep parts of the ocean is important, we need to pay attention to shallow sea areas as well.
- MitaShallow sea areas? What are you careful about?
- KogaWhen deciding on the route, we try to avoid precious fish beds and coral reefs in consideration of the environment. Also, if the cable gets caught in the dragnet of a fishing boat or the anchor of a ship, it is dangerous. So, in shallow sea areas, we bury the submarine cable under the sea bed, instead of laying it down on its surface. As another precaution, the diameter of submarine cable used in shallow sea areas are larger than those used in deep sea areas so that the cable won't break if it comes into contact with an obstacle.
- MitaThat's surprising. I thought cables were larger in deep sea areas because of the pressure of water.
- KogaBefore I explain, I'd like you to see for yourself (showing actual submarine cables).
- MitaWow, submarine cables are very thin! I imagined something as bulky as a drum can. But these cables are both thinner than the arm of a human!
- KogaAre you surprised? Everyone is surprised when they see an actual submarine cable. Several optical fibers, which I mentioned in the first part of the program, run in the core of the cable. This white thinner one is the submarine cable for deep sea areas. It's 17 millimeters wide. And this one covered with black iron is for shallow sea areas.
- MitaThat's surprising. I thought cables were thicker in deep sea areas because of the pressure of water. The one for shallow sea areas is certainly thicker. This iron shield protects what's inside. I see.