One end of the optical cable is fixed on the shore, and the ship slowly moves to the open sea. While sinking the optical cable or cable into the seabed,

the excavator sinking to the seabed is used for laying.

Ship (cable ship), submarine excavator

1. The cable ship is required for the erection of trans ocean optical cables. When laying, a large roll of optical cable shall be put on the ship. At present,

the most advanced optical cable laying ship can carry 2000 kilometers of optical cable and lay it at a speed of 200 kilometers per day.

Before laying, it is necessary to survey and clean the cable route, clean up fishing nets, fishing gear and residues, excavate trenches for sea going vessels,

release navigation information at sea, and take safety precautions. The submarine cable laying construction ship is fully loaded with submarine cables

and reaches the designated laying sea area about 5.5km away from the terminal station. The submarine cable laying construction ship docks with another

auxiliary construction ship, starts to reverse the cable, and transfers some cables to the auxiliary construction ship.

After the cable reversal is completed, the two ships start laying submarine cables towards the terminal station.

The submarine cables in the deep sea are laid accurately to the designated routing position by dynamic positioning vessels equipped with fully

automatic construction equipment such as underwater remote control robots and automatic positioning.

2. The other part of the optical cable laying ship is the submarine excavator, which will be placed on the shore at the beginning and connected

to the fixed end of the optical cable. Its function is a bit like a plough. For optical cables, it is the counterweight that allows them to sink into the seabed.

The excavator will be towed forward by the ship and complete three tasks.

The first is to use high-pressure water column to wash away the sediment on the seabed and form a cable trench;

The second is to lay the optical cable through the optical cable hole;

The third is to bury the cable, covering the sand on both sides of the cable.

Simply put, the cable laying ship is for laying cables, while the excavator is for laying cables. However, the trans ocean optical cable is relatively thick

and flexible, so the forward speed of the ship should be strictly controlled.

In addition, in the rugged seabed, robots are required to constantly detect the best path to prevent rock damage to the cable.

If the submarine cable is damaged, how to repair it?

Even if the optical cable is perfectly laid, it is easy to be damaged. Sometimes the ship passes by or the anchor will touch the optical cable by mistake,

and large fish will accidentally damage the optical cable shell. The earthquake in Taiwan in 2006 caused damage to many optical cables, and even the

enemy forces would deliberately damage optical cables.

It is not easy to repair these optical cables, because even minor damage will lead to paralysis of optical cables. It takes a lot of manpower and material

resources to find a small gap in tens of thousands of kilometers of optical cable.

Finding a faulty optical cable with a diameter of less than 10 cm from the seabed hundreds or even thousands of meters deep is like looking for a

needle in a haystack, and it is also very difficult to connect it after repair.

To repair the optical cable, first determine the approximate location of the damage by sending signals from the optical cables at both ends, then send

a robot to precisely locate and cut off this optical cable, and finally connect the spare optical cable. However, the connection process will be completed

on the water surface, and the optical cable will be lifted to the water surface by the tugboat, and connected and repaired by the engineer before being

put into the seabed.

Submarine cable project is recognized as a complex and difficult large-scale project by all countries in the world.