In the area of wireless communication, free space optics (FSO) has become well-known for its extremely large bandwidth, unlicensed spectrum, and low power secure transmission. Despite the benefits, atmospheric turbulence and fog weather conditions have a significant negative impact. In this study, various modulation techniques are examined when air turbulence and fog are present. Modeling the turbulence as a gamma gamma distributed channel yields the appropriate expression of bit error rate (BER), and for this channel condition, 16- PPM has outperformed other techniques. For the evaluation of channel performance, BER is taken into account. This study can assist in selecting a modulation method that is appropriate for the channel situation. Turbulence or a misalignment between the transmitter and receiver are the causes of pointing inaccuracy. Range pointing inaccuracy and attenuation can cause increased BER and link failure in long FSO links. High power losses can be brought on even even a slight pointing error shift.