Home Forums SYSTEM How to get the BER from the PAM4 eye diagram in MMF system

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    • #16605
      Yizhou Liu
      Participant

      Hi,

      I did a PAM4 through MMF simulation. But I cannot get the correct BER after regenerate the signal. I want to know how to get the BER from the PAM4 eye diagram. Or there is another tool can do it in optisystem.

    • #16616
      Damian Marek
      Participant

      Hi Yizhou,

      As an M-Ary signal there are two main ways. One using a BER Test Set that compares an input sequence to and output sequence exactly, but needs long bit sequences to calculate very small BERs.

      Or like in the attached example, using a constellation diagram and a custom target file also attached. I made a PAM4 scheme and a custom target file to calculate the symbol error rate and the error vector magnitude. Make sure before running you correctly define the directory of the .dat file in the Constellation Visualizer properties.

      Cheers

      +2
      • #17347
        Yizhou Liu
        Participant

        Hi Damian,

        Could you attach the target file again. There is no .dat file in the attachments. Also where I can see the symbol error rate and the error vector magnitude.

        Thanks

        • #17357
          Damian Marek
          Participant

          Hey,

          Sorry about that! In the project file I checked the results to display underneath the electrical constellation diagram.

          Regards

          Attachments:
        • #17562
          Yizhou Liu
          Participant

          Hi Damian,

          Thank you for your reply. By the way, is it possible to use multi mode fiber in your PAM direct detection. I tried to replace the Laser and SMF in your diagram with Spatial VCSEL, Parabolic-index MMF and Spatial PIN photo-diode. The BER Test Set gives me results, but the Electrical Constellation Visualizer seems not work well. Could you help me check my setting in the attached files.

          Thank you

          Attachments:
    • #17564
      Yizhou Liu
      Participant

      I used the same target file you provided to me last time.

      • #17602
        Damian Marek
        Participant

        The problem here is that the Laser has been changed and is now operating at different powers for the different symbols. I had tweaked the .dat file to match the other Laser settings. You can either tweak the new laser to have the same power levels as the original (better option) or modify the .dat file to reflect the new levels.

        Regards

        • #42457
          Santiago Echeverri
          Participant

          Hello Damian,

          I was wondering if you know of a way to script the Target values so that they scale proportionally to the output power at the photodiode. I am thinking about doing a sensitivity curve where the estimated BER is plotted against received power or even signal to noise ratio.

          One Idea that comes to mind is to generate many .dat files with known scaling, but If you know of a more automatic way it would be very useful.

          Regards,
          Santiago

          +1
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