For the purpose of revisiting the semiconductor optical amplifier (SOA) ability for large-band amplification in the context of wavelength division multiplexed (WDM) coherent systems, we numerically investigate nonlinear impairments brought by SOA for polarization multiplexed quadrature phase-shift keying and polarization multiplexed 16-quadrature amplitude modulation terrestrial transmissions. In order to provide a deep understanding of these impairments, we perform a step-by-step approach by assessing the transmission performance of a sole SOA cascade and an SOA-amplified transmission system using linear and then nonlinear fiber. For the same purposes, we also study these impairments for a single-channel transmission even though the final goal is to design a WDM SOA-amplified system with a larger bandwidth than the EDFA-based systems. We show some interesting results on the span-after-span accumulation of SOA nonlinear impairments, as it has been done similarly for the fiber nonlinearities, in the context of dispersion managed or unmanaged coherent systems. Design guidelines of both SOAs for amplification purposes and SOA-amplified transmission systems are derived from this investigation. Finally, we point out promising results for SOA-based transmissions, for particular system configurations that follow these guidelines