Visible Light Communication

In summary, the conversation discusses the use of LEDs in VLC and why visible light cannot be modulated like radio waves. It is explained that the frequency of visible light is too high for electronics to respond, and there are no materials other than electrons that can carry an electric signal. The conversation also mentions the use of modulation techniques in long-haul optical fiber links and the challenges of using amplitude modulation for analogue signals.
  • #1
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I read that for VLC, they use toggling the LEDs ON/OFF to represent binaries. Why cannot we modulate the visible light like radio waves.
 
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  • #2
The frequency is far too high for electronics to respond, so we aren't able to modulate a signal in the same way we can with a radio wave.
 
  • #3
I guess that is because "electronics" are made to handle lower frequencies of radio waves. Why cannot we make compatible electronics.?
the question is, can we modulate light? Handling is different issue.
 
  • #4
Modulating and handling go hand in hand. To modulate a radio signal, the signal is generally created by the electronics and sent through the wires, whose electrons are able to respond to the frequency. Visible light oscillates too quickly for the electrons to respond, and since all materials depend on electrons to carry the signal, if they can't oscillate back and forth with the signal then the signal can't propagate. There aren't any materials that can handle light because there are no particles other than electrons that can carry an electric signal. So we can't make new electronics because the materials simply don't exist.
 
  • #5
Hmm...got it...thanks :-)
 
  • #6
RAHIL008 said:
I read that for VLC, they use toggling the LEDs ON/OFF to represent binaries. Why cannot we modulate the visible light like radio waves.
You can modulate the intensity of the light beam---by driving the LEDs with current that has a component proportional to the amplitude of the audio signal. But digital signal transmission can be made more immune to interfering sources, including sunlight.
 
  • #7
As already said, amplitude modulation is often used in optical communication systems. However, other modulation techniques have been used as well. Here is a good paper from Stanford reviewing modulation schemes used in long-haul optical fiber links:

www-ee.stanford.edu/~jmk/pubs/mod.and.det.tech.COTA.6-06.pdf

:)
 
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Likes Drakkith
  • #8
Thanks for the link, Berkeman, I wasn't aware we were using those modulation methods in fiber optics. Am I correct in assuming they are still using either the light from the original laser or from another source to mix with/interfere with the signal and perform modulation/demodulation?
 
  • #9
Drakkith said:
Thanks for the link, Berkeman, I wasn't aware we were using those modulation methods in fiber optics. Am I correct in assuming they are still using either the light from the original laser or from another source to mix with/interfere with the signal and perform modulation/demodulation?
The LED or semiconductor laser can be pulsed on and off with its power supply.
 
  • #10
Analogue transmission by Amplitude Modulating light tends to be hampered by non linearity of emitters and sensors. Frequency Modulation is difficult, too. One form of modulation by an analogue signal is to use pulse width modulation. The level of the light signal is binary (switched on of off) - so linearity doesn't matter and the timing of beginning and ends of the pulses is easy to make proportional to the analogue signal you want to carry.
 

1. What is Visible Light Communication (VLC)?

Visible Light Communication is a wireless communication technology that uses visible light, such as LED bulbs, to transmit data. It works by modulating the intensity of light at a very high speed, which is then received by a photodetector and decoded into data.

2. How does VLC differ from other wireless communication technologies?

VLC differs from other wireless communication technologies, such as Wi-Fi and Bluetooth, in that it uses visible light instead of radio waves to transmit data. This makes it more secure, as visible light cannot penetrate walls and can be contained within a room.

3. What are the advantages of using VLC?

VLC has several advantages, including high data transmission rates, low latency, and high security. It also has the potential to be used in areas where radio frequency communication is restricted, such as hospitals and airplanes.

4. Are there any limitations to VLC?

One limitation of VLC is that it requires a direct line of sight between the transmitter and receiver, meaning obstacles such as walls can disrupt the signal. Additionally, VLC is still a relatively new technology and may not be widely available in all devices yet.

5. What are some potential applications of VLC?

VLC can be used for indoor positioning, wireless internet access, and data transfer in places where radio frequency communication is not allowed. It can also be used for communication in underwater environments, as water does not disrupt visible light signals.

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