Optical Submarine Cable Repair Method

Categories: Technology
Posted: July 16, 2021

There is a case in which an optical fiber cable is cut or damaged due to ocean earthquakes and fishing gears etc..
In the situation, the cable ship is urgently dispatched to the cable failure site and repairs the cable.
The cable repair procedure normally consists of the followings:
  1) Localization of the cable failure point.
  2) Recovery of the failure cable onto the ship
  3) Cutting and removal of the cable failure section
  4) Jointing of the recovered cable and the spare cable in the cable tank of the ship
  5) Confirmation test and reburial of the cable

Optical Submarine Cable Repair Procedure

1. The distance of the cable failure location from the landing station is estimated by several tests in advance. The cable ship is navigated to the location by DGPS. At the place, the tool for cable search and cutting, which is attached to the rope end, is paid out to the sea. By dragging the grapnel tool on the seabed, the cable is cut.

2. The rope with the grapnel at its end is paid out from the ship, and one end of the cut cable is caught by the grapnel(Cable Catch), and is recovered to the ship(Cable Recovery). It might take more than one day to recover the cable from the sea of 8,000m depth. The optical fiber test and electrical test of its power feed conductor is carried out. If there is still a failure, the cable is recovered further, the failure section is cut and removed.

3. At the end of the cable from which the failure section is removed, the waterproof treatment is carried out. After the attachment of the mooring rope and buoy to it, the cable is once dropped in the sea. The cable ship moves for searching the other end of the cable, and repeats the same procedure as above item 2.

4. The optical fiber test and electrical test of its power feed conductor on the recovered cable is carried out in the same way as above item 2. If there is a failure, the failure section is cut and removed. The cable is jointed with the spare cable which is stored in the cable tank(normally, Universal Joint technology is used). The cable ship approaches to the previously installed buoy together with paying out the spare cable.

5. Holding the spare cable, the cable ship recovers the cable attached to the buoy again, and joints it with the opposite end of the spare cable. For the final confirmation, the test is held between two cable landing stations of the cable. After the confirmation of the communication normality, the on-board cable is released to the seabed, and the repair work is completed.