We use different forms of electromagnetic radiation to function lots of forms of technology. For example, Radio waves and Microwaves are commonly used for wireless tech because of their low frequencies which create a much longer range.
But how exactly are 1’s and 0’s put into them?
In: Engineering
There are different methods. The standard on and off is one method. There’s also frequency shift keying where a carrier wave on the signal will shift frequencies carrying data of a one or zero based on the frequency of the carrier wave being sent. So, there would be the standard sine wave of the signal and then it would have what would look like noise along the wave, but is actually a specific frequency indicative of a 1 or 0.
0/1 is the same as on/off (amplitude modulation) or green/red (frequency modulation) or up-down/left-right (linear polarization) or clockwise/counter-clockwise (circular polarization), etc…
As long as you can distinguish two different state, you can decide one state is 0 and the other is 1. Note that if you can distinguish between 4 states, then you can transfer 2 bit at a time, etc…
Many different ways.
The simplest is continuous wave (CW). This is what Morse code uses. Basically you transmit for 1, and do nothing for 0.
Another is amplitude modulation (AM). This is actually an analog transmission method, but I assume you weren’t asking just about digital. Basically you have a carrier wave of a set frequency. This is the frequency you tune to, e.g. 1000 kHz. Then you have whatever you want to transmit, like the waveform of someone’s voice. You basically multiply the waves together: when the person is speaking loudly, the fast wiggles on the carrier wave are much stronger, and vice versa.
Frequency modulation (FM) is another analog method. Basically instead of changing the amplitude of the carrier wave, you slightly change the frequency. If the person is talking loudly, the frequency gets a little bit higher (say, from 100 MHz —> 100.001 MHz), and vice versa. The digital analog of this is frequency-shift keying (FSK), where for a given carrier frequency (say 100 MHz), a 0 is some small frequency below that (say, 99.999 MHz) and a 1 is some small frequency above it (say, 100.001 MHz).
There are lots of other methods too.
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**TL;DR** Light has a lot of things that describe it. An arbitrary wave can be written E(x, t) = A(x)*exp(-ik(t)x+ phi(t)t). That looks complicated but basically all it shows is every light wave has at least three things we can change: it’s amplitude A(t), its frequency k(t), or its phase phi(t). If we have some message (like a voice recording) that we call M(t) (imagine the waveform of a voice), we can basically arbitrarily pick one of these three things in light to set equal to our message, and send it. For AM this means A(t) = M(t), and so on.
In real life there are no 1’s and 0’s. There’s just varying levels of things.
To put 1’s and 0’s on something you have to define what it means to do that. So we say, “if the wind is strong that’s a 1. If it’s not windy it’s a 0.”
If it’s somewhere in the middle we throw a flag and start checking parity bits and whatever other error correction we have in hopes we can figure out what was meant to be said. If that doesn’t work or is impossible to resolve then we blame the source for the error, because they need to send clearer signals.
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