Hybrid Free Space Optical Communication and Radio Frequency MIMO System for Photonic Interference Separation

We propose and experimentally demonstrate a hybrid free space optical (FSO) communication and radio frequency (RF) multiple-input and multiple-output (MIMO) system for interference separation. The system switches between FSO and RF MIMO modes and makes use of the complementary advantages of the two modes. The MIMO receiver separates signal of interest from in-band interference with blind source separation (BSS), while the separation ratio is limited by the physical dimensions of the MIMO antenna array. With FSO channel, the system achieves over 30dB signal to interference plus noise ratio, so the wireless system can transmit signals with high orders of modulation. When the FSO channel is blocked and line-of-sight transmission condition is not satisfied, the system switches to the RF MIMO mode for interference cancellation. The wireless system maintains continuous transmission at a lower bit rate. Both the FSO mode and the RF MIMO mode can be seamless integrated with photonic signal processing system for wideband and real-time interference cancellation.