INVESTIGATION OF THE EFFECT OF ATMOSPHERIC TURBULENCE ON FREESPACE OPTICAL COMMUNICATION SYSTEMS

Free-space optical communication systems are becoming increasingly popular for high-speed wireless communication applications. These systems utilize beams of light to transmit information over a distance, and they can achieve data rates of several gigabits per second. However, atmospheric turbulence can severely impact the performance of these systems. This paper investigates the effect of atmospheric turbulence on these systems and explores possible mitigation techniques. Atmospheric turbulence is a natural phenomenon that occurs when air currents with different temperatures and densities mix. These fluctuations can cause errors in the received signal, and ultimately lead to a degradation in the performance of these system. One of the main effects of atmospheric turbulence on these systems is scintillation. Scintillation refers to the rapid fluctuation in system. These fluctuations can be modelled as a lognormal distribution, where the standard deviation of the distribution depends on the strength of the turbulence and the length of the link. Scintillation can cause errors in the received signal, which can lead to a decrease in the signal-to-noise ratio (SNR) and an increase in the bit error rate (BER). Another effect of atmospheric turbulence on these systems is beam spreading. Beam spreading refers to the widening of the beam as it propagates through the atmosphere. This widening can be modelled as a Gaussian distribution, where the standard deviation of the distribution depends on the strength of the turbulence and the length of the link. Beam spreading can cause a decrease in the received power, which can lead to a decrease in the SNR and an increase in the BER. One technique is adaptive optics, which involves the use of a deformable mirror to correct for the distortions caused by atmospheric turbulence. The deformable mirror can be adjusted in real-time to compensate for the phase and amplitude fluctuations of the received signal. Adaptive optics can significantly improve the SNR and reduce the BER of these systems, but it is also expensive and complex.