Numerical Investigation of SOA Nonlinear Impairments for Coherent Transmission Systems Based on SOA Amplification

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 un-managed 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.