Photonic-Assisted RF Self-Interference Cancellation with Improved Spectrum Efficiency and Fiber Transmission Capability

An approach to photonic-assisted carrier-suppressed single-sideband radio-frequency (RF) self-interference cancellation with improved spectrum efficiency and fiber transmission capability is proposed for in-band full-duplex radio-over-fiber systems. The key to achieve RF self-interference cancellation is to generate two single-sideband signals with one having a received signal with the RF self-interference signal and the other having only the RF self-interference signal, which is implemented by using a dual-polarization binary phase-shift keying (DP-BPSK) modulator. By controlling the arrival time and power of the electrical signals applied to the DP-BPSK modulator, the RF self-interference can be fully cancelled, and only a carrier-suppressed single-sideband signal with modulation is obtained. In addition to self-interference cancellation, the received signal can be directly converted to an optical baseband signal, so that the spectrum efficiency is increased. An experiment is performed. The results show that a cancellation depth of around 40 dB for a single-frequency self-interference and around 22 dB for a 100-Mbaud QPSK modulated wideband self-interference is achieved.