Low-Distortion Amplification of Probabilistic Shaped Signals Using SOA

The utilization of probabilistic constellation shaping (PCS) has played a pivotal role in facilitating numerous groundbreaking achievements toward approaching capacity limits in recent optical fiber communication experiments. We experimentally demonstrate the low distortion amplification of 32 GBaud PCS 16QAM signal shaped using Maxwell Boltzmann distribution, using a semiconductor optical amplifier (SOA). To compensate for the nonlinear distortions incurred during amplification, we saturate the SOA using a CW laser (termed as holding beam) within the SOA gain bandwidth and centered at 1510 nm. We show the improvement in normalized general mutual information (NGMI) compared to scenarios where no holding beam is employed. We experimentally demonstrate that for low distortion amplification, the holding beam power required for the shaped signals is significantly lower. Additionally, our experiments validate the capability of achieving low distortion amplification of PCS 16QAM signals across the entire C band, underscoring the versatility and efficacy of this approach.