Enhancement of SOA-Based Scintillation Mitigation by PS-OOK Transmission in FSO Communication

This paper proposes an enhancement of semiconductor optical amplifier (SOA)-based scintillation mitigation by polarization shift on-off keying (PS-OOK) transmission in free-space optical (FSO) communication. The scintillation effect is a critical issue in a vertical FSO link. The issue of the extinction ratio (ER) degradation of the received OOK signal caused by the high dynamic gain frequency of the SOA limits the performance of the turbulence-induced scintillation effect mitigation using a gain-saturated and polarization-independent SOA. Therefore, a PS-OOK signal, which has the characteristics of orthogonal polarization of bits '1' and '0,' is transmitted at the transmitter end and a linear polarizer is deployed after the gain saturated SOA at the receiver end. Based on the polarization orthogonality of PS-OOK, the performance of the scintillation-effect suppression is significantly improved by the mitigation of the ER degradation by the blocking of the polarization of bit '0' of the received optical PS-OOK signal using the linear polarizer. The proposed scheme is experimentally verified utilizing the Mach-Zehnder modulator (MZM)-based fading simulator accommodated various turbulence channels. The experimental results illustrate that the scintillation effect is effectively suppressed by the proposed technique compared to the SOA-based conventional single-polarized OOK detection and balanced PS-OOK detection.