Due to the relatively high cost of deploying optical fibers, free space optical (FSO) links have been developed as a cost-effective alternative technology for next generation cellular networks. However, in order to have a practical role in the physical layer of future communication systems, data rate of FSO links must be improved. To this aim, in this paper we employ a multiple-input multiple-output (MIMO) multiplexing scheme with two transceivers to increase the data rate of the considered FSO system. Unlike MIMO diversity case, the performance of MIMO multiplexing is significantly affected by interference be- tween parallel channels. To solve this problem, we propose a novel space-time scheme which significantly reduces the interference between parallel channels. We analyze the performance of the proposed scheme in terms of BER and outage probability.