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00:00If the internet cable at the bottom of the sea is cut by a shark, how is it repaired?
00:06First of all, how do we know where the cable broke in the thousands of miles of sea?
00:12From this video, the entire YouTube, TikTok, Instagram and even the entire global tech system
00:18is connected to each other through the internet these days.
00:21And 99% of the internet traffic passes through the hidden cables at the bottom of the sea.
00:29A traffic highway that we use every day but can't see.
00:34Welcome to Zem TV's videos again.
00:37The network of undersea cables is so large that it connects all the continents together.
00:44These cables are laid at a depth of more than 8000 meters,
00:48where the pressure is as much as 5300 kg per square inch.
00:54It's like putting the weight of an African elephant on the smallest finger of a human foot.
01:01Under the pressure, the smallest part of the undersea cable
01:05is passing from Azerbaijan to Turkmenistan under the Black Sea,
01:09which is about 300 km long.
01:13And the largest part is 6600 km long, which has been named the Maria cable.
01:19It starts in Virginia Beach in America and ends at Bilbao in Spain
01:25from the dark depths of the Atlantic Ocean.
01:28If we talk about the cables laid in all the seas of the world,
01:32the total length of all of them is more than 1.4 million kilometers.
01:37So much so that if these cables are wrapped around all the planets and moons of our solar system,
01:44then still so much cable will be left that it can go around the Earth again.
01:50Now, it is obvious that such long cables are not easy to lay at a depth of 8000 meters in the sea.
01:57The cost of laying just 1 km of submarine cable is more than 25 lakh US dollars.
02:05So now you can guess how much it would have cost to lay 14 lakh km of cable.
02:11But after all, what was the need to do all this,
02:14when in today's era, this same work can be done with the help of satellites
02:17and the whole world can be connected wirelessly to each other.
02:21In fact, there are 493 submarine cables in the world.
02:27Each cable can handle data of 4000 terabits in just one second.
02:33Consider it that only 8 million people can stream 4K movies on one cable
02:40and there are such 493 cables.
02:43On the contrary, if this work is done by a satellite,
02:46then only 24,000 people will be able to watch the same 4K movie on one satellite.
02:51Now, to meet people's demands, it will be necessary to install as many satellites as possible,
02:57which will cost more and will require more maintenance.
03:01In comparison to submarine cable, satellite maintenance is more costly and difficult.
03:06And if for some reason there is a major fault in the satellite,
03:10then it will cost 40 crore US dollars to replace it.
03:15This is why it is easier to lay millions of kilometers of cable under the sea
03:19than satellite or wireless connectivity.
03:23In this undersea highway, millions of gigabytes of data are traveling at all times.
03:28This means that this highway will also be very wide,
03:31i.e. these cables will be thicker than a normal fiber optic cable.
03:36But it is not so.
03:38It looks like a yellow and black cable is as thick as a hose pipe,
03:42but in reality, the fiber optic cable passing through it is as thin as hair.
03:47So now the question arises, how so much data is sent through such a thin wire?
03:53This wire is called the fiber optic core, which is made of glass or plastic.
04:00Light passes through it, which travels the data in small packets.
04:06First of all, the data in the computer is converted from electrical signal to light signal
04:11with the help of a transmitter.
04:14The transmitter does this work through laser light or LED.
04:18This light signal is transmitted or sent in the form of a pulse,
04:22which has only two parts, 1s and 0s.
04:26The light pulse shows 1, and when there is no pulse, it shows 0.
04:32Taking these pulses from one place to another is the work of the core,
04:37between which the light travels.
04:39There is a layer outside this core called cladding,
04:43and this layer stops the light from coming out of the core.
04:47If the light tries to come out of the core,
04:50the cladding bounces it back into the core.
04:54This process is called total internal reflection.
04:58Now at a greater distance, this light signal becomes weak,
05:02for which a repeater is installed after every 100 km,
05:06which boosts the light signal.
05:08To complete this part, a layer of copper is applied on the core and cladding,
05:14in which 10,000 volts of DC current is sent.
05:18Because there is no power source in the middle of the ocean,
05:21to power these amplifiers,
05:23a current passing through the copper layer is used.
05:27Fiber optic cables can transmit more than one signal at a time.
05:33This technique is called wavelength division multiplexing, or WDM.
05:39Different colors of light are passed through fiber optics at the same time,
05:43and each color of light has different data packets.
05:47As you know, the speed of light is 1079 million km per hour.
05:54That is, this data reaches from one place to another,
05:57as soon as the blink of an eye from the speed of light.
06:00At a distance of thousands of kilometers,
06:02this data is converted into electrical signals again
06:05with the help of a photodiode or photodetector,
06:08and then the computer or mobile device reconstructs it again
06:12and brings it into graphics or any other form.
06:16In addition to the core, cladding and copper layer,
06:18the reason for the thickness of the submarine cable is that
06:21there are seven more layers on top of it,
06:24whose job is to save the cable from the extreme pressure of the water.
06:28But despite this, this cable is damaged by earthquakes,
06:31shark attacks and volcanic eruptions in the sea.
06:36But the biggest reason for the damage of the submarine cable is fishing.
06:41Some vessels hunt for fish living at the bottom of the sea with this trawl door,
06:46which has a rope attached to it that is directly connected to the vessel.
06:51This trawl door is pulled to the ocean floor by sending it to the bottom,
06:56and then the fish get stuck in it.
06:59When this trawl door is accidentally thrown in the place of the submarine cable,
07:03the cable suffers a lot of damage due to the pulling.
07:07Now here you must be having the same question in your mind,
07:10that if the submarine cable is damaged at the bottom of such a vast and vast sea,
07:15then how is it repaired?
07:18It is a matter of time to fix it,
07:20but first of all, how is the location of the thousands of kilometers of wire damaged pinpointed?
07:27Let me tell you here that today's modern submarine cables are 1 inch thick
07:33and the weight of a kilometer of wire is about 1400 kg,
07:37that is as much as a sedan car.
07:39For installation in the sea, such thousands of kilometers of wire
07:43are installed in one piece at the bottom of the sea with the help of special ships.
07:48After complete research, when a special area is chosen,
07:52then the large rolls of wire are loaded into the ship and brought to that location.
07:57And a special robotic machine, which has the ability to walk on the sea floor,
08:02is used to dig the floor up to 1 meter and the cable is laid in it.
08:08This is a very slow work, which is very important to do with great care.
08:14According to an estimate, it took about 2 years to install the 6600 km wire
08:20laid between the US and Europe.
08:24When the wire in one vessel runs out,
08:27a second vessel filled with cable is ordered and the first corner of the wire
08:31is connected to the new wire and the work of laying is proceeded.
08:35The biggest obstacle in all this work is the weather.
08:39The Atlantic Ocean has a series of high winds 365 days a year
08:45and when these winds take the form of a sea storm, no one can stop them.
08:52In addition to this, there is often a category 1 hurricane in the Atlantic Ocean.
08:57Even now, when I am researching for the video,
09:00there is a category 1 hurricane in the Atlantic Ocean,
09:04which will reach the coast of Ireland on August 23 according to the forecast.
09:09Due to hurricanes or strong storms, installation work is paused there for many days
09:15until the weather is clear.
09:18Now when the work of installation is so difficult,
09:21imagine how difficult the work of repair will be.
09:24There are data centers at both the end points of the submarine cable
09:28that monitor the activity of the cable 24x7.
09:32As soon as the connection between the two breaks,
09:35it means that the cable has broken in the middle of the sea.
09:39To find out exactly where the wire of thousands of kilometers has been damaged,
09:44a special device is used, which is called the Optical Time Domain Reflectometer.
09:49This device sends a light pulse from both ends
09:53and because the cable is broken, that light pulse bounces back.
09:58The pulse that comes back, how long did it come back
10:01and how much strength of the signal is left,
10:04it is estimated that exactly how many kilometers after the cable is damaged.
10:09This process is done from both ends
10:12and it is verified that the location of both is the same or not.
10:16Now from both ends, the DC supply, i.e. the current left in the cable is turned off
10:22and the ROVs are sent to the bottom of the sea at that location.
10:26With the help of ROVs, the cable is first physically checked
10:30and then the cable is taken out and brought to the vessel above.
10:35The damaged part of the cable is cut and a second piece is attached to it.
10:41Because the fiber optic core is made of glass,
10:44this work has to be done very carefully
10:47so that one glass is attached to the other as if it was in one piece.
10:52This process is called splicing.
10:55If the cable is less or the bottom of the sea is very low,
10:59then first one part is lifted up,
11:02the second extra wire is attached to it and laid down again.
11:06Then the same process is done on the other end of the broken wire.
11:11How does the benefits of submarine fiber optic cable work?
11:16You may have got the answer to many questions about installation and repair.
11:22We hope you will like and share this video of ZemTV.
11:26Thank you very much for your loving comments.
11:29See you in the next great video.

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