Multiple input multiple output (MIMO) technology with equal gain-combining (EGC) is Considered in this work to Enhance the data rate of free-space optical communication (FSO) system in log-normal channel. In FSO system, Propagating light in free space is used to transmit data for communication system. 256-ary pulse position modulation (PPM) using intensity modulation with Direct Detection (IM / DD) as a power efficient system is employed using PIN receiver. Obtained results Demonstrate That significant boost of data rate can be Achieved using MIMO techniques. Enhances data rate from 350 Mbps to 800 Mbps When using 2 × 2 MIMO configuration. As well, is reported about 1 Gbps for 4 × 4 MIMO system. These enhancements are Achieved without any bandwidth or power expansions and the bit error rate (BER) at the receiver is maintained below 10 ^-3.