Electromagnetic Waves: How & Why They Store Info

[physixlover]

How does the electromagnetic waves store information, what makes these waves to store. (this may be a stupid question but i need to know how)

Thanks.

 

[Matterwave]

Information (the kind that we humans use) can be stored in turning the EM wave on and off (kinda like Morse code, but a lot more complicated). This turning on and off mechanism is why higher frequency EM waves can "store" more information, since they can be turned on and off at higher frequencies without destroying the wave.

This method is used for Fiber Optics I believe (I'm not 100% since I haven't really studied this).

 

[jtbell]

Here are two schemes that are used for carrying information on radio waves:

http://en.wikipedia.org/wiki/Amplitude_modulation

http://en.wikipedia.org/wiki/Frequency_modulation

 

[Tao-Fu]

It's up to you to modulate the properties of a light field in some way so as to allow someone later to measure these modulations and extract data from them. A simple way might be to send a train of pulses whose polarizations are set to be either vertical or horizontal (as defined by me). I can associate bit values with these two physical states and transmit a bit stream to a person who knows to measure polarizations with a beam splitter (oriented in the correct direction) and a couple of photodetectors.

In principle you could use just about any physical property of an E/M field to encode information (frequency, spatial mode, pulse duration, pulse energy, polarization, etc.).

More generally, you can store information in any physical system whose properties you can arrange in specific ways.

 

[physixlover]

thanks guys,good posts ,your posts will be very helpful for my research