Home Forums SYSTEM coherent detection 16 qam wdm optical ofdm

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    • #30569
      mukalla pavan
      Participant

      hi
      i want to replace 16-qam instead 4-qam in coherent optical qam wdm optical ofdm..but i am getting bit error rate of 0.483

      please suggest me the changes needed

      i am attaching the file

    • #30596
      alistu
      Participant

      Hi Mukalla,

      I have noticed a few parameters in your system that need to be changed. First of all, the number of cyclic prefix points should be the same both for OFDM modulators and demodulators. Second, The value of symbol rate should be set according to the coding scheme in layout parameters and in OFDM blocks. Please see if these help.

      Regards

    • #30687
      mukalla pavan
      Participant

      thank you alistu

      with the changes you suggested system working somewhat better. But still ber of 0.35 in one channel and 0.26 in another

      what to do to reduce ber ?

      • #30741
        alistu
        Participant

        You’re welcome. Can you please upload the new .osd file in which you have made the aforementioned changes? I also believe the bandwidth of some of the filters is a bit more than what is required, but even so the system is supposed to work properly after the above changes are applied to it.

    • #30785
      mukalla pavan
      Participant

      i am uploading new osd file

      • #30803
        alistu
        Participant

        Hi Mukalla,

        having done the changes that I suggested, you have very clear constellation diagrams, which shows transmission is done correctly. However, in order to overcome the symbol rotation, you can change the receiver laser phase so that constellation points fall into the correct quadrants.

        Regards

    • #30952
      mukalla pavan
      Participant

      ok alistu

      i will try by changing laser phase at receiver

      thank you

      • #31007
        alistu
        Participant

        Hi Mukalla,

        Please see if the change in the laser makes the BER zero when the constellation points are all in their corresponding quadrant for your 16-QAM and 64-QAM implementations. Otherwise, the problem you are facing may be due to the fact that OS12 OFDM components have been used in your design.

        Regards

    • #30843
      Ranjeet Kumar
      Participant

      Here, I am uploading a new osd file bidirectional wdm ofdm pon. May this file help you to solve your problems.

      • #31031
        alistu
        Participant

        Hi Ranjeet, Thank you very much. I find your implementation quite helpful.

        Mukalla, The file attached by Ranjeet is quite helpful for your purpose. The thing is, it is a bidirectional system due to being implemented as a passive optical network. But you can easily make changes to make it suitable for your own purpose if bidirectionality is not desired.

        Regards

    • #31379
      mukalla pavan
      Participant

      Thank you alistu and ranjeet kumar

      changes in laser not giving BER 0

    • #31383
      mukalla pavan
      Participant

      i am not understanding ranjeet kumar file
      could you please explain me clearly how it helps to solve my problem

      thank you

      • #31389
        alistu
        Participant

        Ranjeet’s file is a simulation of a bidirectional OFDM system and is designed for the purpose of being used in passive optical networks, while your simulation should be unidirectional. So I suggest you eliminate parts of the system corresponding to upstream data to have the unidirectional system.

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