The submarine communication cable is a wire wrapped with insulating material, which is laid on the seabed to realize the telecommunication transmission between countries. The first submarine communication cables, which began to introduce telephone communications and Internet communications, and the modern fiber optic cable, also known as submarine cable.

How to lay?

In simple terms, the submarine cable laying is placed on the submarine cable laying on the submarine cable, and then slowly move the ship while the cable tile sank to the seabed.
Specifically, the cable laying mainly includes three stages of optical cable route exploration, cable laying and flush protection. Cable laying is usually caused by mining submarine cable laying machine to complete, it is a bit like when plowing plow used by submarine cable laying ship towed forward, and through the cable to make all kinds of instruction. There are rows of water hole, the bottom of the operation, at the same time each hole toward the bottom of the sea spray high pressure water column, the seabed sediment burst, the formation of cable trench. The upper part of the device has a cable hole, used to guide the optical cable (cable) to the bottom of the optical cable trench.
 

 
Cable laying ship of France Telecom (data)
In the past, it was often used to allow sand to cover the ditch naturally, so as not to bury the cable. And now usually with high pressure pump underwater robot into a ditch and then put it into the soil.
How “ antiseptic ”?
Because of the long-term immersion in sea water with high concentration of sea water, it is easy to be corroded by seawater. In addition, the hydrogen molecules will diffuse into the fiber glass material, so that the loss of fiber. Therefore, the submarine cable to prevent internal hydrogen generation, but also to prevent hydrogen from the outside into the optical cable. At present, the structure of the submarine optical cable is that the optical fiber is wrapped around the center of the optical fiber after being processed once or two times.
 

 
Submarine cable structure (data)
The basic structure of submarine optical cable is usually: polyethylene layer, polyester ester or asphalt layer, steel strand layer, aluminum waterproof layer, polycarbonate layer, copper or aluminum pipe, paraffin, paraffin layer, fiber bundle, etc.. Therefore, the diameter is usually 69 mm, the weight of up to 10 kilograms per meter, the design life of continuous work for 25 years.
How to repair?
Submarine cable is often faulty, sometimes from ships, sharks and other casual destruction, sometimes the enemy's deliberate destruction, more often caused by the earthquake caused problems. For example, by the Taiwan earthquake in 2006, a number of international submarine communications cable interruption, resulting in domestic Internet users can not normally visit foreign websites. Similarly, in 2011, affected by the earthquake in Japan, a number of submarine cables through the relevant waters of Japan failure, and then many Chinese users found unable to log on the u.s..
Compared with the laying of fiber optic cable, fiber optic cable repair increasing difficulty, because from a depth of several hundred meters or even thousands of meters on the seabed to find problems of the cable diameter less than 10 cm, like look for a needle in the ocean, and then adjourned after the restoration of the difficulty is very big.
Usually, the general submarine optical cable fault treatment will go through several steps. First, the spread spectrum time domain reflectometry is used to locate the fault location. After that, through the diving robot to find the exact location of the damaged submarine cable, cut off the location of the fault, and the two ends of the tow back to repair the ship repair. Next, connect the two break points of the damaged optical cable with the spare submarine cable, and then put it back to the seabed.