Comparative Study of the Performance of Different Modulations in FSO Communication over a Turbulent Channel with Pointing Error

Free Space Optical (FSO) communication is a method of transmitting data using modulated light waves through free space, such as air or vacuum, instead of using traditional wired or fiber-optic cables. FSO systems typically use lasers or light-emitting diodes (LEDs) as light sources to transmit data, and photodiodes or other light detectors to receive the data. In this paper, we investigate the error performance of a Free Space Optical system using various modulation techniques under different intensity fluctuation conditions. Our analysis takes into account the combined effects of atmospheric turbulence-induced fading and misa-lignment fading on the propagating signal. We derive novel closed-form expressions for the statistics of the random attenuation of the propagation channel for each modulation scheme used. Additionally, we perform a comparative study of bit-error rate (BER) performance for all modulation techniques considered in this work. We present numerical results to evaluate the error performance of all modulation schemes used in FSO systems with the presence of atmospheric turbulence and/or misalignment. Furthermore, we compare the OOK, PPM, DPSK, and BSPK modulation techniques to determine the best modulation that achieves the minimum BER for a given signal-to-noise ratio value equal to 30 dB in different scenarios.