SOA Nonlinearity Aware Longitudinal Power Profile Estimation

Power profile estimation (PPE) enables access to the longitudinal power evolution in a fiber link using only a coherent receiver and digital signal processing. We demonstrate in this paper that semiconductor optical amplifiers (SOAs) can degrade the power profile estimation process for both correlation and linear least-squares based PPE methods. We show this effect via numerical simulations for the SOA deployed both as a single channel booster as well as a wavelength-division multiplexing (WDM) in-line amplifier. We then propose a solution which is based on digital modeling of the SOA nonlinearity in order to correct this effect. We examine the degradation of the power profile for various combinations of SOA parameter variations as well as the tolerance of the proposed solution to the accuracy of these parameters. The numerical findings are validated by an experimental demonstration of a PCS16QAM signal at 90 Gbaud transmitted over 5 spans of single mode fiber and utilizing an SOA booster after the transmitter. The results confirm that by leveraging the proposed method and accurate SOA characterization, the obtained power profiles obtained with an SOA are as accurate as the EDFA power profiles.