How do you find a breakpoint when an undersea cable breaks?

The general procedures for handling submarine cable incidents are as follows:

1. The spread spectrum time domain reflectometer (SSTDR) is also used to locate the fault location. The instrument uses the principle of time-domain reflection. It transmits and receives a set of signals first, because a cable accident usually breaks the internal fiber, and the new breaking position will reflect the signal, the recovered reflected signal is compared with the applied mathematics and time calculated by the algorithm to pinpoint the exact location of the fiber breakage. The Optical time-domain reflectometer sends a simple pulse of light (just a square wave) to the fiber, detects the reflected signal, and calculates it in combination with the passage of time. The shorter the pulse of light it can emit, the higher the accuracy of the instrument. The distance shown on the instrument = elapsed time × optical fiber refractive index at the speed of light in a vacuum. The refractive index of the fiber should be set by itself. It's as simple as that. This backscattering method is easy to obtain enough precision, so some international standardization organizations, such as the International Telecommunication Union (ITU) can use it to measure fiber attenuation, length, and so on. And it's the only fiber-optic method that can detect breakpoints. First, because there is a small amount of scattering (Rayleigh scattering) in the fiber, the instrument receives a small amount of scattered signal (noise) at all times during the measurement. At the same time, the fiber always attenuates (including Rayleigh scattering) , the reflected signal is always getting weaker and weaker, and the curve on the instrument is constantly falling.

2. Cable repair ship to the location of the accident, repair. If the water depth is less than two kilometers, usually using underwater robots, through artificial signals to guide to the fault, will be damaged cut off the fault location, the remaining two ends will be towed back to the repair ship for repair.

3. If the water depth is more than 2000 meters, because of pressure problems, will change to the use of deep water grab, image is a hook. If it's a sandy seabed, the cable is hooked back up to the surface. If it's a rocky seabed, the grab needs to follow the cable for a certain length, so that it can be positioned more to avoid getting caught on the rock.

Four. If the water is too deep, a single grab can not pull the entire cable directly to the surface. At this point, the need to cut the fiber optic cable, now take one end of the A1 buoy fixed, and then use another grab to pull the other end of the A2.

5. Fiber optic cable repair is mainly a fiber optic welding work, a 2 and the new standby cable B welding, and then repair ship close to the buoy, a 1 and B to the rest of the welding, the repaired cable is deliberately longer than the original length, and the new cable is U-shaped on the seabed. After the completion of welding to wait for communication test success after the cable back.