Submarine optical cable laying and its fault treatment
How is the submarine optical cable laid? How does submarine optical cable prevent corrosion by seawater? How to repair if there is a fault?
Submarine communication cables are wires wrapped with insulating materials and laid on the seabed to realize telecommunication transmission between countries.
The first submarine communication cables provided telegraph communication, and later telephone communication and Internet communication were introduced. Modern optical cables also used optical fiber technology, so they were called submarine optical cables. How to lay?
To put it simply, submarine optical cable laying is to lay the optical cable on the submarine optical cable laying ship, and then the ship slowly starts to sink the optical cable to the seabed at the same time.
Specifically, cable laying mainly includes three stages: cable routing investigation and cleaning, cable laying and burial protection.
Cable Laying is usually completed by the cable burying machine digging the seabed. It is a bit like a plow used in ploughing. It is towed forward by the submarine cable laying ship and makes various instructions through the working cable.
There are several rows of water spray holes at the bottom. During operation, each hole sprays high-pressure water column to the seabed at the same time, flushing the seabed sediment to form a cable trench.
The upper part of the equipment has a guide cable hole to guide the optical cable (Optical Cable)To the bottom of the cable trench.
In the past, sand was often naturally covered on the ditch by sea currents to save time for burying cables.
Now, an underwater robot equipped with a high-pressure water pump is usually used to wash a ditch and then put it in and bury the soil.
When laying optical cables, the water-entry angle and laying tension of the optical cables should be controlled by controlling the sailing speed and release speed of the laying vessel to avoid damaging the optical cables due to too small bending radius or too large tension.
During the laying of the deep sea section, the cable laying vessel releases the optical cable, and uses the underwater monitor and the underwater remote control vehicle to continuously monitor and adjust to control the forward speed, direction and speed of the laying vessel, to avoid damaging optical cables by bypassing uneven places and rocks. How to 'antiseptic '?
Submarine optical cables are extremely vulnerable to seawater corrosion due to long-term immersion in seawater with high concentration.
In addition, hydrogen molecules will diffuse into the glass material of the optical fiber, making the loss of the optical fiber larger.
Therefore, the submarine optical cable should not only prevent hydrogen from being generated internally, but also prevent hydrogen from infiltrating into the optical cable from the outside.
At present, the structure of the submarine optical cable is to wrap the optical fiber spirally after one or two coating treatments in the center to strengthen the components (Made of steel wire)The bag is around.
The basic structure of submarine optical cable is usually: polyethylene layer, polyester resin or asphalt 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 69mm, the weight per meter is as high as 10 kg, and its design life is 25 years of continuous work. How to repair?
Submarine optical cables often fail, sometimes inadvertently destroyed by ships, sharks, etc. , sometimes deliberately destroyed by the enemy, and more often caused by earthquakes.
For example, due to the earthquake in Taiwan in 2006, many international submarine communication cables were interrupted, resulting in domestic internet users not being able to visit foreign websites normally.
Also in 2011, affected by the earthquake in Japan, many submarine optical cables passing through Japan's related sea areas failed, and then many Chinese users found that they could not log on to the US website.
Compared with laying optical cables, the difficulty of repairing optical cables is increasing, because finding a problem optical cable with a diameter of less than 10 centimeters from a seabed as deep as several hundred meters or even several kilometers is like looking for a needle in a haystack, however, it is also very difficult to continue after repair.
In general, the general submarine cable fault handling will go through five steps.
First, the spread spectrum time domain reflector is used to locate the approximate fault location.
After that, find the exact location of the damaged submarine optical cable through the diving robot, cut off the fault location, and drag the remaining two ends back to the repair ship for repair.
Next, use the spare submarine cable to connect the two breakpoints of the damaged cable, and then put it back to the seabed after testing.