Photonic-Assisted Multipath Self-Interference Cancellation for Wideband MIMO Radio-Over-Fiber Transmission

To cancel the multipath self-interference at the receiver of a wideband in-band full-duplex (IBFD) multiple-input multiple-output (MIMO) radio-over-fiber (RoF) transmission system, a photonic-assisted approach is proposed and experimentally demonstrated. A multipath optical tunable delay line (MOTDL) module with a large adjusting arrangement and high tuning precision is designed to manipulate the local reference signals, which are modulated onto several optical wavelengths and then poured into the MOTDL via a dense wavelength division multiplexer (DWDM). By tuning the time delay and attenuation of each path in the MOTDL, all the self-interference signals can be cancelled from other local transmit antennas of the MIMO RoF transmission system, and the desired radio frequency (RF) signal can be recovered. A proof-of-concept experiment is carried out to verify the feasibility. Results show that at the receiver of a 3 × 3 MIMO RoF transmission system, the multipath self-interference cancellation depths of 30.18 dB, 24.9 dB, 22.7 dB, and 20.88 dB at 16.6 GHz are achieved for the bandwidths of 100 MHz, 500 MHz, 1 GHz, and 2 GHz, respectively.