超奈奎斯特(FTN)技术可以提高无线光通信(OWC)系统的频谱效率，但信号在传输过程中会受到人为引入码间干扰(ISI)和大气湍流的影响，导致系统误码率(BER)性能恶化。针对此问题，文章构建了4阶脉冲幅度调制(4PAM)的多输入多输出(MIMO)FTN-OWC系统，通过采用MIMO技术抑制了大气湍流对信号的影响。在此基础上，推导了该系统在Log-normal信道下的理论BER，并分析了信道间相关性对系统BER性能的影响。仿真结果表明，当BER为10^-4时，2×2 MIMO-FTN系统的BER性能较单输入单输出(SISO)-FTN系统提高了9.5 dB。当信道相关且相关因子低于0.6时，MIMO-FTN系统的BER性能优于SISO-FTN系统。

Faster-than-Nyquist (FTN) technology can improve the spectral efficiency of Optical Wireless Communications (OWC). However, it is affected by the artificially introduced Inter-Symbol Interference (ISI) and atmospheric turbulence, which leads to the degradation of Bit Error Rate (BER) performance. To deal with this issue, a PAM modulated Multiple Input Multiple Output (MIMO)-FTN-OWC system is proposed, and MIMO technology is utilized to suppress the influence of atmospheric turbulence. Furthermore, the theoretical BER in log-normal fading channel is deduced, and the influence of channel correlation on the BER performance is analyzed. The simulation results show that the BER performance of 2×2 MIMO-FTN system is 9.5 dB higher than that of Single-Input Single-Output (SISO)-FTN system when BER is 10^-4. In addition, the MIMO-FTN system has better BER performance than that of SISO-FTN system when the channel spatial correlation coefficient is lower than 0.6.