Multi-section semiconductor optical amplifiers (SOA) have been shown to have superior
noise and linearity performance compared with single section SOAs. We show how to create
a simplified numerical model for multi-section SOAs that is suitable for optical communication
system simulations and use that model to investigate the amplification performance of 56 Gbit/s
four-level pulse amplitude modulation signals. We find that a multi-section SOA could provide an
improvement in input power dynamic range exceeding 3 dB compared to a single section SOA that
has the same unsaturated gain.