Phase shift at ofdm demodulation

Discussion in 'Wireless & RF Design' started by thavamaran, Oct 24, 2010.

  1. thavamaran

    Thread Starter Active Member

    Feb 21, 2008
    Hi there guys, I am having some problem at OFDM receiver. Actually I am doing optical ofdm.

    My back to back ofdm is perfect. zero erros at no noise and with noise it matches the theoritical bit error rate of 16 qam.

    But including my laser model, my laser will be modulated by the ofdm signal, and after i receive it. The constellation point shifted by 45 degree.

    I tried to equalize it which is very trivial in OFDM. But after equalizing it, I realize its not linear phase shift, it shifts by 45, then 135 randomly.

    I modelled the laser rate equation which is nonlinear differential equation with Euler method numerical method. And my receiver doesnt have any synchronization.

    Can anyone suggest me where the problem would be? Need more explanation, please let me know and I will be more than happy to explain it in detail. Thank you.