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M-ary threshold

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(joined April 2021)
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Hello everyone

Does anyone know how to determine the threshold and output amplitude at M-ary threhold?

I didn’t understand why in this link (https://optiwave.com/resources/applications-resources/optical-system-digital-modulation-dpsk/) the defined threshold amplitude is – 0.85, -0.353, 0.353 and 0.85?

Responses (3):

    • #69311
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      Agatha Binka
      Participant

      Hello everyone

      Does anyone know how to determine the threshold and output amplitude at M-ary threhold?

      I didn’t understand why in this link (https://optiwave.com/resources/applications-resources/optical-system-digital-modulation-dpsk/) the defined threshold amplitude is – 0.85, -0.353, 0.353 and 0.85?

    • #69319
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      Ahmad Atieh
      Moderator

      Dear Agatha,
      typically, you need to view the eye and based on it, you determine the thresholds. You choose them in the center of the eye in every region.
      You need to place the Electrical Eye Viewer component in front of the PAM Decision component to view the eye.
      Please note that you need to use small bit sequence length (maybe 2048 bits) to avoid blocking the eye view.
      Regards,
      Ahmad

    • #69339
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      Agatha Binka
      Participant

      Dear Mr. Ahmad Atieh,

      Here i attach the electrical eye diagram from PAM system (C:\Users\USER\Documents\OptiSystem 18.0 Samples\Advanced modulation systems\PAM systems). Can you tell me how to read the threshold by marking a cross at the point which is the threshold reference from the eye?

      Attachments:
    • #69348
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      Ahmad Atieh
      Moderator

      Dear Agatha,
      you should set the threshold at 110uV, 400uV and 640uV. These levels are in the center of each eye.
      Regards,
      Ahmad

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