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(joined November 2019)
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Hello everyone

How can I make a simple Tx-fiber-Rx system with QAM modulation? From the existing sample in the optisystem using QAM followed by OFDM, can I use QAM modulation without OFDM? Then, How to measure the BER value? because when I try to make a simple system from QAM samples in https://optiwave.com/resources/applications-resources/optical-system-manchester-and-pam-codingdecodingdigital-modulation-qam/ the BER value is 0

Thank you

Responses (6):

    • #69043
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      Nabila
      Participant

      Hello everyone

      How can I make a simple Tx-fiber-Rx system with QAM modulation? From the existing sample in the optisystem using QAM followed by OFDM, can I use QAM modulation without OFDM? Then, How to measure the BER value? because when I try to make a simple system from QAM samples in https://optiwave.com/resources/applications-resources/optical-system-manchester-and-pam-codingdecodingdigital-modulation-qam/ the BER value is 0

      Thank you

    • #69047
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      Ahmad Atieh
      Moderator

      Dear Nabila,
      please check the example (112Gbps SP-16QAM_B2B_subsystem with DSP_Investigating Power level calculation.osd) located at the following link in OptiSystem Example Library. This example is for 16QAM. However, it can be modified for other QAM levels. I hope this helps you.
      When the BER is 0, the system performs perfectly. On the other hand, when BER is 1, the system is causing all bits to be erroneous.
      C:\Users\USER NAME\Documents\OptiSystem 17.1 Samples\Advanced modulation systems\QAM systems\16 QAM

      Regards,
      Ahmad

      • #69048
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        Nabila
        Participant

        Thank you Mr. Ahmad

        i already check the example. However, i want to know what the difference between the ber test set and the BER analyzer? can i change the ber test set to BER analyzer

        i already check another advance modulation system example, all of them use ber test set

    • #69049
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      Ahmad Atieh
      Moderator

      Dear Nabila,
      you may check the theory used in each component by referring to the datasheet that can be accessed by right clicking on the component and selecting the component properties, then choosing Help.
      The BER Test set is suitable for advanced modulation where you have decoding process at the receiver. The problem when using BER analyzer with decoded signal is the removal of all distortions that the pulses acquire through the transmission in the system.
      Regards,
      Ahmad

    • #69107
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      Nabila
      Participant

      Hello Mr. Ahmad
      Can i change the DSP and decision component in the example (112Gbps SP-16QAM_B2B_subsystem with DSP_Investigating Power level calculation.osd) with m-ary threshold? i try to make simple QAM system without OFDM and DSP component, but the BER results show a value of 0.5 or 0.49, what is the maximum value of BER that is good for a system? from what I know a good BER is 10 ^ -9 but the BER test value doesn’t seem to show the minimum BER value like in the BER analyzer

    • #69108
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      Ahmad Atieh
      Moderator

      Hello Nabila,
      If I understand you correctly, you wanted to use the PAM receiver of the example (PAM fiber link w Threshold Detector.osd) with QAM system. Please note that the output of the DSP is a normalized output with QAM levels, not voltage as the PAM decision system. you could use the PAM decision if you split the I and Q signal and receive each separately.
      Regards,
      Ahmad

    • #69110
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      vanaja 01
      Participant

      (Awaiting moderation)

    • #69112
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      Nabila
      Participant

      Dear, Mr. Ahmad Atieh
      can I ask further? I’ve tried to contact you via email

      Thank you in advance

      Regards, nabila

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