I understand it’s just signals and 1s and 0s but don’t the signals overlap in the undersea cables?
In: Engineering
it’s not a single wire it’s hundreds of fiber optics strands, and inside of each you can have several different colours (technically wavelength) of light without interfering with each other, further more each wavelength cal blink several billion times a second to transmit information, so it’s a lot of capacity
ther are also signal repeaters every once in a while so the signal doesn’t get too weak to be picked up
also the fact that lots of people are using it doesn’t really matter as that’s handled by IP, every packet of information sent has a destination and origin address, so it can independently reach its destination, the cable just sends it, the stuff at the other end knows where to forward it to regardless of how it gets therr
Yes and no. The signals overlap in the sense that they are broken up into chunks, sent separately, and then reassembled, so a bit of my post may be sandwiched between a bit of a YT video and a bit of someone’s email. But the various pieces of hardware that make up the internet know how to break up, track and reassemble all those pieces so we all get what we want (most of the time).
If you’re thinking that the cables are thin so the signals must be “crashing into” each other, well, you’re half right. The cables are thin, at least at human scales. Actually, the entire cable is thick, but it is made up of lots of really thin strands. It’s just that the thinness is apparent only when we think in everyday human scales. To a photon/electromagnetic wave (which is how the information moves through the cables), there is a huge amount of room to maneuver without impeding the flow of all the other photons/waves simultaneously moving through the cable. It’s the difference between two people trying to pass by each other in a normal doorway versus ten-thousand gnats trying to pass by each other in a normal doorway. The humans can barely scrape by, but the gnats likely won’t notice each other. And gnats are absolutely enormous when compared to a photon.
They do, but networking is designed to handle that.
Your data is broken up into chunks called packets. The beginning of each packet tells the networking equipment where it came from and where it’s going – called a header (a bit like sending a letter in an envelope).
So it doesn’t matter if the packets arrive out of order or mixed in with somebody elses (in fact they are designed to), the networking equipment at the other end just reads the header and forwards it on to it’s destination.
An undersea cable contains anywhere from 8 to 24 individual fiber strands. Within each fiber strand the operator of the network uses DWDM or dense wavelength division mulltiplexing which is the concept of using multiple wavelengths of light to communicate multiple different networks on the same strand of fiber. When you combine that with multiple strands of fiber you have very good scaling capabilities. For example, you could deploy 24 strands of fiber with 30 wavelengths of light on each fiber being multiplexed together to deliver 720 completely different networks which themselves are being multiplexed as Ethernet packets.
[Time Division Multiplexing](https://en.wikipedia.org/wiki/Time-division_multiplexing). Lots of it.
Very high frequency (fast) modulation and demodulation (aka modems, but for fiber optics).
[Blinkenlights](https://en.wikipedia.org/wiki/Optical_fiber)
Edit: Looks like Fiber uses [Wavelength Division Multiplexing](https://en.wikipedia.org/wiki/Wavelength-division_multiplexing).
In Time Division Multiplexing, instead of sending one signal over one “wire,” multiple signals are broken up into multiple segments, which are sent one after another, in order to send multiple signals over one wire.
With Wavelength Division Multiplexing, the signals operate on different wavelengths (frequencies), which are able to work across the same wire without interfering with each other. Because fiber optics operate on light, these wavelengths manifest as different colors. Similar to how different radio frequencies can exist over the air, and you can tune a demodulator (a radio) to the frequency of the signal (radio station) you want to pick up.
First off you take all the 1’s and 0’s and bundle them up, then you do some maths so you can tell if any go missing or get mangled in transit and tag the answer to that on the end of the bundle, then you convert all those 1’s and 0’s into flashes of light REALLY fast, then you run them through a prism so you can send lots of different colours of light down the same cable at the same time.
At the other end you do the reverse – split the colours out, un-bundle the package, check that you get the right answer and if not ask the other end to send it again.
In the middle you can add signal boosters that knock all the blurry edges off the flashes and boost them back up to full power.
One under-sea cable can have 100’s of individual fibres so multiply many colours by many fibres and the fact you can send flashes REALLY fast and there you go.
It’s like how a highway can let thousands of people get to different at the same time.
The data is sent in packets for each person using it. Think of those like the cars. But there are lots of lanes and all the cars aren’t in the same place at the same time. The cars are travelling at almost the speed of light so they don’t stay long either.
Lots of lanes, fast cars.
They don’t *collide* because we divide them in send/receive pairs. The simple way is to dedicate one strand to send and one to receive, which is opposed on the other side. That way you are always listening on one strand and always sending on the other. At that point, it is just a matter of the data waiting its turn to be sent or listened to. We typically don’t dedicate an entire stand to this, we break the stand into wavelengths, sometimes you might hear an engineer say “we are sending on blue and taking on red” or something, they are literally talking about the part of the spectrum correlated to the colors we see.
That is the physical side, for routers on each side, they are dumb and fast. All they do is broker data packets, and it is done fast enough that a VOIP (telephone call over the internet) between France and the USA will work without very much issue.
The data is sent (mostly) sequentially. So all the data has to get into a line of 1’s and 0’s, which get sent across the ocean. Once the data arrives on the other side, it gets split up and sent to the various people that are supposed to receive it.
The undersea cables are *really* fast and can send multiple billions of 1’s and 0’s every second and they contain multiple cables (it’s not just one big cable, it’s a bundle of hundreds of cables).
In addition, you can use different colors of light. So you’d have a red laser firing into the fiber optic cable, but also a blue and a green laser. This lets you send multiple streams of 1’s and 0’s simultaneously since different colors of light don’t really interfere with each other. At the receiver end, they have a prism which splits the light into separate streams, one for each color, and then each stream of 1’s and 0’s gets split up and sent to the recipients.
When you send a message or browse the internet, this information is turned into tiny light or electrical pulses. These pulses travel through the underwater cables just like water moves through pipes.
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