Acousto-optical modulators for free space optical wireless communication systems

A free space optical (FSO) wireless communication system is proposed and analyzed in this paper. An incident laser beam is aligned to hit a Bragg cell at the Bragg angle. At the same time, input data bits to be transmitted control the frequency of the RF signal, which in turn controls the acoustic wave propagating in the Bragg cell. As such, different diffracted beams will be obtained based on the frequency of the generated acoustic wave signal in the Bragg cell. The different beams represent variant signals in a constellation diagram and will be used to convey information from the source to the destination. A receiver with multiple photodetectors aligned to the variant diffracted beams is considered. An optimum receiver should consider the different angles and intensities of the transmitted beams to retrieve information bits. The average bit error probability of the wireless communication system is obtained through Monte Carlo simulations and validated analytically. Besides, the impact of different system and channel parameters is investigated. Reported results reveal significant enhancements of the proposed algorithm as compared with conventional state-of-the-art FSO systems.