system
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human
ELI5: Can someone help me understand how all the different television channels are transmitted to a television?

Are all the hundreds of channels being transmitted all at once single optic cables and we just select a frequency to tune into? That just seems ridiculous with the amount of information that needs to be transmitted.
gpt
Fiber (or fibre) optic television service works very differently to traditional cable television services, so it's important to clarify which one you're talking about.

With traditional cable television systems, the copper cable that comes into your home is shared with your neighbors. The cable company allocates different frequencies to different television channels and carries the data streams for all television channels on the same cable simultaneously to everyone in the neighborhood. 

When you want to watch a particular channel, you use a tuning device (aka a 'tuner') to select specific frequencies and demodulate the signal to recover the original data stream for that particular television channel broadcast. Other frequency bands are reserved for other types of data communications (e.g. internet connections and phone services).

Fiber optic television services work very differently. Typically speaking, they operate on Internet Protocol (IP), hence why these services are often called IPTV services. This basically means every device (including your television / set-top box) is assigned a unique IP address as part of a data/computer network and when you want to watch a particular channel, your television / set-top box sends a request to the IPTV server for the data stream of that channel. 

After authenticating, a copy of the data stream for that television channel is sent back from the server through the fiber optic cable into the home where it is routed (as data packets) to the television set-top box that requested the stream whereby the video stream gets decoded and is displayed for viewing.

IPTV services are more complicated though because they typically (although not always) use multi-casting protocols to improve distribution efficiency. This means that instead of, for example, sending individual copies of a television channel stream from the server to you and your neighbor (who is also watching the same channel), the service provider instead sends one stream to your local neighborhood node and then that neigborhood node then sends individual copies of the stream to your house and your neighbor's house. This reduces the amount of bandwidth required to deliver the stream between the service provider's main routing facilities and smaller regional areas like neighborhoods.

Also, yes, you're right that in a traditional cable provider setup, the TV streams do take up tons of bandwidth. Each channel can take anywhere from 5-20 Mbps of bandwidth on average and since all channel streams are carried simultaneously, that means that there may be well over a gigabit worth of bandwidth on the cable dedicated just to TV alone. If cable companies re-built there infrastructure to work on an on-demand system like IPTV, then lots of bandwidth could be repurposed for other uses (e.g. faster internet speeds).