Nonlinearity, noise and bandwidth influence for PAM4 modulation format

PAM4 is a modulation format of interest for optical short and medium range communication. Noise, nonlinear characteristics and component bandwidth have a complex relationship influencing the system performance. The interdependency is investigated for PAM4 by means of error vector magnitude. It will be shown by numerical simulations that with increasing noise and nonlinearity, narrowband filtering becomes more and more important in order to achieve good system performance. Additionally, it can be stated that the maximum input power should stay 3 dB below the 1 dB compression point of the nonlinear characteristic in order to mitigate nonlinear influence.