This study used wireless orthogonal frequency-division multiplexing (OFDM) combined with optical code division multiple access (OCDMA) technology and applied multi-input multi-output (MIMO) architecture with neural network algorithm in a free space optical (FSO) channel. Walsh-Hadamard coding technology was used in this system as each user’s codeword, which used the characteristics of fixed cross-correlation between each group of Walsh-Hadamard codewords and effectively eliminated interference between base stations at the receiving end using a balance test. In the rainy climate, when the number of users is 25, the data transmission rate is 10G (bit/s), and the effective receiving power is of -22 dBm, the BERs without- and with- neural network algorithm are 2.41*10^-4 and 8.48*10^-10, respectively.