Power Allocation for Quantum-Limited Multihop Free-Space Optical Communication Systems

In this paper, we propose two novel power allocation strategies for multihop Free-Space Optical (FSO) networks with any number of hops. These strategies correspond to the analytical solutions obtained from minimizing two different upper-bounds on the conditional error probability under the quantum-limit scenario. The performance of the first strategy is evaluated numerically and closed-form expressions of the average probability of error are derived for the second strategy. We also quantify the reduction in the fading variance and scintillation index provided by multihop FSO systems associated with the second power allocation scheme that compromises performance for simplicity. Results show the superiority of the proposed schemes compared to the equal power distribution strategy.