Opt Lett. 2018 Jul 1;43(13):3124-3127. doi: 10.1364/OL.43.003124.
A photonic approach for simultaneous wideband radio-frequency (RF) self-interference cancellation and frequency downconversion in an in-band full-duplex radio-over-fiber system is proposed based on a dual-polarization quadrature phase-shift keying (DP-QPSK) modulator. The upper dual-parallel Mach-Zehnder modulator (DP-MZM) in the DP-QPSK modulator is used to cancel the self-interference directly in the optical domain and generate two sidebands of the desired RF signal, whereas the lower DP-MZM generates two sidebands of the local oscillator. After detecting the combined optical signal at a photodetector, the desired RF signal is downconverted to an intermediate frequency (IF) signal with the self-interference cancelled. The proposed approach can overcome the reappearance of the interference signal and the power fading effect of the received signal caused by fiber dispersion. An experiment is performed. The cancellation depth for single frequency interference cancellation is around 58 dB, whereas that for the wideband interference cancellation is larger than 25 dB. The fading effect of the proposed IF transmission system is also evaluated compared with the traditional RF transmission system.
提出了一种基于双偏振正交相移键控（DP-QPSK）调制器的在带全双工光纤射频系统中同时实现宽带射频（RF）自干扰消除和频率下变频的光子方法。DP-QPSK 调制器中的上双平行马赫-曾德尔调制器（DP-MZM）用于在光域中直接消除自干扰，并产生所需 RF 信号的两个边带，而较低的 DP-MZM 则产生本振的两个边带。在光电探测器处检测到组合光信号后，所需的 RF 信号被下变频到中频（IF）信号，同时消除了自干扰。所提出的方法可以克服光纤色散引起的干扰信号再现和接收信号功率衰落效应。进行了实验。单频干扰消除的消除深度约为 58dB，而宽带干扰消除的深度大于 25dB。与传统的 RF 传输系统相比，还评估了所提出的 IF 传输系统的衰落效应。
