Thanks for the answers! My biggest takeaway is about how bits work using different frequencies, and how fiber optics can use different colors to help organize data
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For fiber optic cables, they add a bunch of different frequencies (“colors”) at once. So your house uses the red light and the next house uses orange, etc.
Ons and offs are actually pretty rudimentary. Now advanced encoding schemes exist that allow more bits per symbol.
Routers commonly use a scheme with 128 possible amplitude and phase shift values, allowing for 8 bits per symbol instead of 1 at a time.
There’s also fiber optic, which is intently faster and can interlace different colors simultaneously to increase bandwidth.
Then all of the data is tagged with where it needs to go.
Fiber internet works just like the ethernet in a building.
Data is broken into smaller units called packets and like letters in the mail each packet has a source and destination address or IP address. This helps the devices figure out where to send the traffic. (If you want to be pedantic there’s a lot more involved than that, but this is the ELI5 answer)
The fiber optic cable is like a water pipe. It is able to carry internet for lots of homes because no 1 home needs 100% of what the pipe can carry. Also not everyone is using the internet / taking a shower at once. If they do, everyone slows down. You get less water pressure because everyones tap is on at the same time.
Cable modems and Cable TV go a step further. Each signal or TV channel on the coax cable uses a set frequency that’s different than the other. Just like different stations on a radio. The Cable Internet signal just happens to take frequencies that aren’t used by the TV.
Think about how a single freeway supports many travelers, all traveling in parallel lines of cars. A one-lane offramp also supports many travelers, just not as many, in a single line of cars. Each car has its own destination, even if they share a freeway or off-ramp.
There are many ways that internet is distributed to homes, but all of them use a mix of parallel lanes and single lanes. They are usually fast enough that an individual user doesn’t notice that they are sharing the road with lots of other drivers.
packets are coded with ip addresses, passwords & vlans. i’m actually curious what % of network traffic on fiber optic is actual data.
For copper based internet like with cable TV, and to a certain amount it’s also true for DSL, the signal is much more complex than just 0s and 1s. Along with being encoded on many frequencies allowing for many different data-carrying channels, just like how radio has many frequencies, each signal isn’t just a single bit. Though you transmit at a fairly high rate, each thing you transmit represents many bits, requiring a bit of processing to get the binary data back.
The analogy is that you can transmit a low, medium-low, medium-high and high signal as representing the binary codes 00, 01, 10 and 11 respectively, and get double the data throughput. If you can easily discriminate between even more ranges of low/medium/high signals, you can transmit even more bits at once. However the actual signal encoding on cable is more complex than that and capable of transmitting 4, 8 or even 12 bits at once making the speeds very good on each frequency.
This does make cable internet vulnerable to signal interference as it becomes harder to tell the difference between adjacent signal levels in the face of a bit of static on the line, but coaxial cable in general tends to be well shielded, and the fact that it has to be screwed down onto the modem or TV receiver is part of that shielding. Try to screw it down about as tight as your fingers will allow, even if that means you need a small wrench to remove it later.
As for aiming the signal to the right home, often you don’t. DSL modems are on a private pair of wires for each home, but cable is shared along the local neighbourhood, being split from hardware not all that different from a cable splitter you can buy at an electronics store. Cable modems are designed to be more controlled by the internet provider than the home user – at least the types with only 1 data port – and is intentionally ignoring any data not intended for itself, only relaying data that belongs to you.
In a purely digital system you can still take turns, for example if the cable can handle 10GBit or 10 billion bits per second, and you have 10 computers all trying to download different movies at the same time, if you have a machine to organize them and make them take turns, they can each get 1Gbit.
Other kinds of cables send analog, in which case you can share in time or also in frequency. Like with radio waves an analog signal can be split into frequency channels, like 100MHz, 200MHz, 300MHz, and so on.
It’s like radio. You can tune to one radio station and get a totally different channel with totally different programming from another radio station. Well, someone eventually figured out that you can also send radio over a cable rather than over the air and that lead to the creation of cable TV. Well, someone also figured out that just like your cable company can talk to you, you can also talk to your cable company for things like internet. It’s just a more advanced version of a walkie-talkie so they built a box called a cable modem that does two-way communication between you and your cable company.
Every single person on a cable gets their own channel, just like every radio station gets their own channel on the air. The frequency of the information sent over the cable is different for every person so that no two people are talking at once.
The difference between something over the air and over a cable? Over the air, there are different things at different frequencies and it’s shared over a massive area. A radio station might live at 99.5MHz and another might live at 97.9MHz but the radio signal for a military airplane lives at 200MHz so you can’t also send someone’s internet on the same channel. But on a cable, you don’t have to worry about any of that because the only people talking on the cable are those who are connected to the cable. The channels on a cable aren’t shared with the radio going out over the air. Someone’s internet can be at 100MHz and someone’s TV signal can be at 200MHz without worry about anything else so you can fit a lot more conversations and channels into one cable.
Fiber is the same way. The color red is not the color green, so you can send two signals with different colors down the exact same cable and not have them bump into each other. At the other end of the fiber, there’s some complicated tech that can tell the difference between red and green and get two totally different signals out of it!
other great answers here. In addition to everything they said there’s a simpler mechanism at work as well.
It works the same way your mail truck can carry your mail as well as the mail for everyone else on your street. Yeah, it’s all 1’s and 0’s, but some of those are addresses and equipment is reading them and using them to make decisions about what goes where.
in different scenarios this is either operates like a “switch” or a “bus”/”hub”.
“Switched” here would mean a device receiving a bunch of traffic, and forwarding each packet exactly once, and only to exactly where it needs to go. Efficiently sorting one stream into many smaller streams.
A “hub” or “bus” topology is where all the paths can see all the data, and each listening device is just configured to listen for its own address, seeing but ignoring any traffic that belongs to anyone else.
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