Performance of different modulation scheme in free space optical transmission – A review

The Free-Space Optical (FSO) Communication (FSOC) system employs line-of-sight (LOS) technology. For long-distance transmission, FSO uses an optical bandwidth to attain data rates of gigabits per second (Gbps). In the FSO system, several vital difficulties comprising Atmospheric Turbulence (AT), Pointing Error (PE), along with weather-reliant atmospheric attenuation should be resolved. By adding more spatial degrees of freedom, the impacts of fading could be efficiently mitigated by a Multiple-Input, Multiple-Output (MIMO) FSO. In this research, the different modulation techniques’ performance (with or without Space Diversity Reception Technique (SDRT)) utilized in FSO systems is analyzed. Concerning Outage Probability (OP), Bit Error Rate (BER), along with Signal-To-Noise Ratio (SNR), the outcomes are analyzed. M-ary Quadrature Amplitude Modulation (M-ary QAM) and an Orthogonal Frequency-Division Multiplexing (OFDM)-centered FSO system is capable of long-distance communication (7000 m) at data rates ranging as of 4.1 Gbits/s (min) to 10.94 Gbits/s (max) as per the findings.