Communicating with Light
Contributed by Jon Luntzel
- How do you hear your friends when you’re talking to them on the computer, gaming, on the phone?
- How come messages can go so quick even though the earth is so big?
- How can a device we’ve built keep track of a signal, when there’s so much information in it? Does it know exactly what’s happening at every fraction of a second?
- How fast could it go?
- How might we detect small packets of information such as light? Can you think of any examples of where we need to know if something is there or not?
- Sound recorder (phone)
- Software (Matlab)
- No risk
- Record an audio file
- Plot frequency / time of the audio file
- Read it in using audioread(filename)
- Divide the signal into equally sized segments (signal analyzer toolbox) choose no overlap for simplicity
- compute the power spectrum of each segment, then take the mean frequency of each segment to build a discrete signal
- Plot frequency / time again
- Convert each segment into binary based on frequency, send the string to someone else, have them reconstruct it (visual of fiber optic signal)
- Other person saves the signal as a .wav file (use the audiowrite method) and play it back, choosing different segment sizes to show the effect
Physics Concepts and Questions
- How would this help us send a signal using a technique like fiber optics?
- Signal compression. Explain how it’s important, because finite resources, technological constraints, convenience
- Digital vs. Analog
Conclusions and Further Investigations
- How would we do this for an image, or other kind of message?
- What might be a short way of telling the other person what they need to know to reconstruct it? General method for dealing with any binary signal?