How submarine optical cable is laid across oceans?

How to lay the submarine optical cable?

In particular, the cable laying mainly includes the cable routing investigation and cleaning, the cable laying and the protection of three stages. Cable laying is usually done by excavating the submarine cable, which is a bit like plough used in plowing, towed forward by submarine cable-laying vessels, and makes various instructions through the working optical cable. There are several rows of blowhole at the bottom of the operation, each hole at the same time to the seabed spray high-pressure water column, the seabed silt burst into a cable trench. and the upper part of the equipment has a guide cable hole, used to guide the optical cable (cable) to the bottom of the cable trench.

In the past, the sand was often used to cover the ditch so as to avoid the time of embedding the cable. And now it usually uses an underwater robot equipped with a high-pressure pump to flush a ditch and put it in and then bury the soil.

For each submarine cable length, there should be no connector in the middle of the cable. When laying ,a full cable should be in the bottom of the sea, by controlling the sailing speed of the ship, cable release speed to control the cable into the water angle and the laying of tension . To avoid the too small bending radius to damage the cable, the laying vessel in the sand and mud area, high-pressure flushing to form a trench about 2 meters deep, the cable buried in, and then covered with sand next to achieve the purpose of protecting the cable; in coral reefs and Clay area, then use the cutting machine to cut a 0.6-1.2 m deep groove, and then buried in the cable trench, and then covered with cement and other hard objects on the cover protection.

How to prevent  submarine optic cable from being corroded?

Submarine cable is very susceptible to seawater corrosion because of its long immersion in seawater with high concentrations. In addition, hydrogen molecules are diffused into the glass material of the fiber, making the loss of the fiber larger. Therefore, the submarine fiber optic cable should not only prevent the internal production of hydrogen, but also prevent hydrogen from external infiltration of optical cable. At present, the structure of the submarine cable is to wrap the fiber in the center after one or two times coating, and the reinforced component (made of steel wire) is wrapped around.

The basic structure of submarine cable is as follows: polyethylene layer, polyester tree ester or bituminous layer, steel strand layer, aluminum waterproof layer, polycarbonate layer, copper tube or aluminum tube, paraffin, alkane layer, fiber bundle, etc. Therefore its diameter is usually 69 mm, the weight of each meter up to 10 kg, the design life for the continuous work of 25 years.

How to protect and repair submarine optic cable?

Submarine cables often fail, sometimes from ships, sharks and other inadvertently damage, sometimes the enemy's deliberate destruction, more time is caused by the earthquake problems. For example, 2006 affected by the Taiwan earthquake, a number of international submarine communication cable interrupted, resulting in domestic internet users can not normally visit foreign websites. Similarly, in 2011, many Chinese users found themselves unable to log on to the U.S. Web site, after a number of undersea cables that were routed through Japanese-related waters were also affected by the Japanese earthquake.

Compared with the laying of optical cables, the difficulty of repairing fiber optic cable is increasing, because the problem of less than 10 centimeters in diameter is found in the seabed up to hundreds of meters or even thousands of meters, which is like a needle in a haystack, and the difficulty of repairing it is very great.

Generally, the general submarine cable fault treatment will take several steps. First, using the spread spectrum Time-domain reflector to locate the approximate fault location. Then, through the submersible robot to find the exact location of the damaged submarine cable, cut off the fault location, and drag the remaining two ends back to repair the ship to repair. 

Next, using the spare submarine cable to connect the two breakpoints of the damaged optical cable, then test it back into the seabed.