EDFA-Based All-Optical Relaying in Free-Space Optical Systems

Free-space optical (FSO) communications has recently received considerable attention for last-mile terrestrial applications and wireless backhaul in mobile communication systems. The performance of these systems is mainly impaired by weather-dependent attenuation and the intensity variations of the channel known as scintillation. The distance-dependence of both attenuation and scintillation motivates the use of relays as a means of improving system performance and extending the communication link. In this paper, we propose an exact and practical model for all-optical relays employing erbium-doped fiber amplifiers (EDFAs), which avoid the optical-to-electrical and electrical-to-optical conversions required in conventional FSO relays employing electrical amplification. The proposed model is shown to be more accurate than existing simplified models and an outage probability analysis for all-optical EDFA-based relaying in the presence of lognormal fading is presented. Our results show that FSO systems with simple all-optical relays achieve a better performance compared to systems with relays employing electrical amplification.