Presently free space optical communication (FSO) is a promising technique on which various researches are carried on. The integration of orthogonal frequency division multiplexing (OFDM) and Subcarrier index modulation, conventional OFDM, Multi input multi output OFDM (MIMO-OFDM) concepts are analyzed in this paper. In free space optical communication these techniques are utilized as well as the performance analysis is simulated using MATLAB. This work investigates the significant of SIM modulated MIMO-OFDM in FSO. Also it analyses the superiority of SIM modulated MIMO-OFDM than SIM modulated classical OFDM and simple Subcarrier index modulation over free space optical communication. Here different turbulence conditions are taken to analyze the concept of SIM along with MIMO-OFDM, classical OFDM in free space. Ultimately SIM modulated MIMO-OFDM exhibits better BER performance in the order of 10-6 in comparison to simple SIM and SIM associated OFDM in free space.