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Indoor Free Space

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(joined May 2015)
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I am using FSO channel as an indoor FSO medium for indoor VLC system but if I used a short length like 1m to 4m the output power signal from the FSO channel get amplified. what is the cause of this? or does it mean that I cannot used the FSO component for indoor simulation. I am really in dilemma.
thanks for your active contributions.

Responses (18):

    • #28787
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      Yahaya Idriss
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      I am using FSO channel as an indoor FSO medium for indoor VLC system but if I used a short length like 1m to 4m the output power signal from the FSO channel get amplified. what is the cause of this? or does it mean that I cannot used the FSO component for indoor simulation. I am really in dilemma.
      thanks for your active contributions.

    • #28788
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      alistu
      Participant

      Hi yahaya,

      Can you please upload your OptiSystem implementation file (the file with .osd format) if it is possible for you to do so? Also, I would be grateful and think it would make participants be able to help better if you share any paper giving some background information on what you are trying to do.

      Regards

    • #28795
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      Yahaya Idriss
      Participant

      Find attached my project file. I want to integrate both the indoor VLC system and OCDMA using the attached file with an ambient light as AWGN.
      I learned from the forum that I can unchecked the geometric loss in the FSO so that the output power signal will not be amplified, but then the signal cannot go beyond 1m if all loss are added. The BER analyzer result is always 1.
      Thanks for your assistance.

      • #28809
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        alistu
        Participant

        Hi Yahaya,

        Your system has very low SNR and it is normal to have this result. If it is not possible to use in-line optical amplifiers in your design, have you tried using power booster with more gain than 10 dB, or using more power for each of the input optical power sources to improve signal to noise ratio?

        Regards

    • #28812
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      Yahaya Idriss
      Participant

      Hi Alistu
      Thanks for the observation. so you mean I should not use in-line optical amplifier?. Generally you are saying that the system has low input optical power from the LED. I will try to implement your suggestion to see the impact.
      Thanks for your assistance.

      • #28813
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        alistu
        Participant

        You’re welcome Yahaya. I am merely saying one way to improve input power is to use LED power. You can also use more gain at input amplifier even though the amplifier adds some noise corresponding to noise figure. You said you can’t use in-line amplifier, so I gave the following suggestions.

    • #28815
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      Yahaya Idriss
      Participant

      Hi Alistu
      I am back again. I have increased the input power of the LED and there is improvement but I find out that there is increase in optical power after passing through the FSO component. Therefore, according to Damian marek he made mentioned in the forum on the topic of AWGN noise where he suggest that the geometrical Loss box in the FSO component should be unchecked. I did so and the problem of increase optical power is solve. However, the result at the BER change very little even when you increased the distance and change the background noise at the AWGN channel. Ideally, in VLC small change in distance like 1m to 2m supposed to show a great change at the BER. Kindly help me to rectify this problem.
      Thanks for sparing your time in assisting me.

      • #28819
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        alistu
        Participant

        I would be grateful if you kindly address the forum page where Damian has made the above suggestion, so that I get to know more about the subject. Besides, can you please indicate the length of the channel that you want your system to have? If it is just 4 meters, the current system already works.

    • #28822
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      Yahaya Idriss
      Participant

      Hi Alistu
      Find the shortcut were Geometric Loss box unchecked was discussed by Damian marek. http://optiwave.com/forums/topic/awgn-noise/
      Actually I intend to use bit rates of 622Mbps to analyzer the performance of both indirect sunlight and Fluorescent lamp individually as attenuation factors on indoor communication channel. The BER analyzer will be use to evaluate out how far this signal can go without any degradation, i.e transmission distance cover.(by plotting a graph of BER against transmission distance). I hope you have get the gist of this project.
      Thanks

      • #28823
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        alistu
        Participant

        Thank you for the link and the provided information. The implementation file that you uploaded in this page already shows great BER change when the length of the channel changed from one to four meters. Isn’t this the remarkable change you mentioned you were expecting to see in your VLC system?

    • #28831
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      Yahaya Idriss
      Participant

      Hi Alistu
      what I expect is a drastic change in BER as the transmission distance is varies. for instance like from 2.3789e-009 to 9.1276e-009 of 3567e-008 not just 1.3667e-009 to 1.2678e-009 which is negligible cannot be shown on the graph.
      Thanks

      • #28834
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        alistu
        Participant

        I see. I believe this remarkable change in signal as it passes through channel should somehow be a result of the channel characteristics, and not the system setup. I managed to get Q-factor of more than 6 for your system for 0.5km. I also omitted the booster and the reach was even less than 4 meters. But in none of these cases the drastic change was observed.

    • #28837
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      Yahaya Idriss
      Participant

      Ok Thanks for your contributions. I think practically commercial white-LEDs cannot go beyond 10m although it depends on the power of the LED.
      Thanks

      • #28843
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        alistu
        Participant

        You’re welcome. It also depends on the power amplifiers being used in your system. If you increase the power amplifier gain (as I did in your system), you can overcome the channel attenuation, which I think is the main cause of signal degradation in your case, and make the reach much longer.

    • #28844
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      Yahaya Idriss
      Participant

      Thanks you. Can I find any component in optiSystem that can convert dBm to dB loss. I want to add in dBm to dB in the FSO component as an attenuation factor. For instance equivalent of -21.76dBm in dB loss.
      Thanks

      • #28848
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        alistu
        Participant

        You have to look to see if the component (for which you want to see the value in dB loss or any other unit) has the unit you want to use in your measurements. If the component doesn’t have it, you can write a program to calculate it (outside OptiSystem) and then apply the value with changed unit (just to make conversions easier).

    • #28860
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      Yahaya Idriss
      Participant

      Ok Thanks for the information.

      • #28861
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        alistu
        Participant

        You’re welcome.

        Cheers!

    • #43277
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      M. E.
      Participant

      hello every one,

      i can not find the attached file of this topic

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