All-optical AF relaying FSO systems using EDFA combined with OHL over Gamma-Gamma channels

In this paper, we newly propose and theoretically analyze the performance of all-optical amplify-and-forward (OAF) relaying free-space optical (FSO) systems using erbium-doped fiber amplifier (EDFA) combined with optical hard-limiter (OHL) over atmospheric turbulence channels. The use of OHL enables OAF relaying FSO systems to remove accumulated background noise, which is one of the main factors that limit the system performance. The performance of proposed systems is analytically studied by which closed-form expression for bit-error rate (BER) is formulated, taking into account the effects of atmospheric turbulence channels and noises caused by background radiation and receiver. The numerical results, which are validated by Monte-Carlo (M-C) simulations, confirm the superiority of the proposed systems in comparison with conventional ones.