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Q-factor doesn\'t change !!!

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(joined May 2014)
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in this model using 4 Qam when i change the input power , the Q-factor doesn’t change to see the effect of fiber non-linearity , it just varies between 0 at lower and higher power levels , otherwise 1*e050 (i.e 10^50) but there is no variations in the value of Q-factor with changing power level , how to solve that .

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    • #13200
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      mai fouad
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      in this model using 4 Qam when i change the input power , the Q-factor doesn’t change to see the effect of fiber non-linearity , it just varies between 0 at lower and higher power levels , otherwise 1*e050 (i.e 10^50) but there is no variations in the value of Q-factor with changing power level , how to solve that .

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    • #13216
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      Damian Marek
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      Hi Mai,

      The BER Analyzer approximates the BER by analyzing the eye diagram. Since there is a threshold detector before it the eye diagram is “perfect”, which results in the unrealistically high Q factor. For QAM modulation it would be better to use either the BER Test Set (with a suitably long sequence) or you could use the error vector magnitude metric, which is generally used for QAM signals. This is calculated by the electrical constellation visualizer.

      Regards

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