Photonics-assisted simultaneous self-interference cancellation and IQ demodulator

A novel approach with photonic-assisted simultaneous self-interference cancellation and IQ demodulator is proposed and experimentally demonstrated for In Band Full Duplex (IBFD) communication system. In this scheme, the X branch of the integrated dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM) is used to generate upper and lower sidebands of the local oscillator signal with a phase difference of 90 ° through bias voltage control, and the received communication signal and the reference signal are loaded on the Y branch, which is used to achieve self-interference cancellation (SIC) by adjusting the delay and amplitude of the reference signal and the bias voltage of Y branch. All the sub-MZMs are worked on Carrier Suppression Double Sideband (CS-DSB) mode, and the upper and lower sidebands, which are separated by dense wavelength division multiplexer (WDM) or some other kind of optical bandpass filter, are used to realize IQ demodulation through two polarization beam splitters (PBS) and balanced photodetectors (BPDs) by adjusting the polarization state. Experimental results demonstrate good gain characteristics of the system during the down-conversion from 10GHz to 30GHz, as well as, the spurious-free dynamic range (SFDR) of 100.7 dB•Hz2/3 is obtained. At the same time, the cancellation results show more than -30 dB cancellation depth from 10 GHz to 25GHz. Besides, IBFD demodulation performance based on 16-QAM under 200Msps, whose carrier frequencies are from 10 GHz to 30GHz, are all demodulated without and with self-interference. All the average depths of communication signal self-interference cancellation have reached over -20 dB when signal-to-interference ratio (SIR) is 0dB, -5dB, -10dB, and all the demodulated error vector magnitudes (EVMs) satisfy the 3GPP-specified EVM limit for 16-QAM signals.