Abstract— In this paper, we propose optical wireless multipleinput multiple-output (OMIMO) with backward spatial filter (BSF) in diffuse channels. In the proposed system BSF is constructed based on the channel state information (CSI) in the transmitter so that the received signal is free from multipath interference, which results in less receiver complexity and good performance. We show that the proposed system can achieve better bit error rate (BER) performance than the conventional single-input single output (SISO) system in diffuse chanels.