Home Forums SYSTEM Low BER in coherent OFDM simulation

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    • #24373
      chee
      Participant

      i wonder why the BER of my system is so low. my system is build according to the example given bu optisystem. i have tried to lower the dsturbance to as low as 3db\km and the range to as short as 100m. stil the BER is around 0.5. is there something wrong with my system? please help me. i have been solving this for 2 weeks now.

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    • #24375
      alistu
      Participant

      Hi Chee,

      It’s a good thing that you started a new topic for this problem. However, I posted a comment on this at the topic below:

      optiwave.com/forums/topic/error-during-simulation/

      I couldn’t find the exact problem with your system, but I used your channel in optisystem sample OFDM implementation and there it worked, at least for a back to back system. Please refer to my answer.

      Regards

      • #24376
        chee
        Participant

        Thank you alistu. the modified BER is 0.37. stil is too high to be accepted. and i found out that even though the attenuation is only 3db and the distances is 100m, the constellation diagram at the receiver is all wrong.

        • #24377
          alistu
          Participant

          You’re right. I was merely suggesting that it seems your implementation of the system is different from that of the sample. For example, I have used your channel in optisystem sample CO-OFDM (see the attached file) and you can see that the error is near to the error given by optisystem sample for a back-to back system. You get BER=0.008 for the system attached below, while the BER for the implementation attached in your post is always around 0.5.

        • #24395
          chee
          Participant

          dear alistu, i noticed that the BER value in the example u attached does not change according to the attenuation. sometimes the BER improves when i increases the attenuation or vice versa. does this means something is wrong with the simulation setup?

        • #24399
          alistu
          Participant

          It seems so… For Optisystem CO-OFDM sample I created a back-to-back system and it still had some value for BER. So I am confused. Since it seems to be a technical problem (along with the other problem you had in your former topic which is not solved yet), I think we can use Damian’s help on this.

        • #24439
          Damian Marek
          Participant

          See my reply here:

          Error during simulation

          I fixed your project a bit and it is giving better BER. You still need to find the proper electrical gain and figure out what your MZM limitations are.

          Regards

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