Abstract
A novel approach to simultaneous radiofrequency self-interference cancellation (SIC) and frequency down-conversion in a unified system is proposed and demonstrated experimentally based on cascade Mach-Zehnder modulators (MZM). The local oscillator signal is injected into the MZM1, whereas the received RF signal and the reference signal are fed into MZM2 and MZM3. After photoelectrical conversion by a balanced photodetector, the desired intermediate frequency signal with SIC is obtained. The cancellation depth for the single frequency SIC with frequency down-conversion is around 38 dB, and that for a wideband signal is around 19 dB. No electrical delay and attenuation are used in the proposed system, so it can potentially reach a wider frequency band and a higher cancellation depth.
Highlights
Compared with time division duplex and frequency division duplex, a full-duplex system improves spectrum efficiency and throughput by using the same frequency band on the uplink and downlink [1]–[3], applied in many fields such as 5G communication system, intelligent traffic control, and radar network [4], [5]
The DC bias voltage of MZM1 is 1.4 V to make it work at quadrature transmission point and the optical signal injected into MZM1 is modulated by signal generator 1 (SG1) (Agilent N5182B), whose frequency of output signal is limited at 6 GHz
The optical carried RF signal in the upper path and the optical carried reference signal in the lower path are sent into a balanced photodetector (BPD) fabricated in our laboratory
Summary
Compared with time division duplex and frequency division duplex, a full-duplex system improves spectrum efficiency and throughput by using the same frequency band on the uplink and downlink [1]–[3], applied in many fields such as 5G communication system, intelligent traffic control, and radar network [4], [5]. The cancellation is achieved by tuning an electrical delay line and an attenuator, so the operational frequency band and cancellation depth are still confined by electronic devices and the same problems appear in [14]. An optical self-interference cancellation with frequency down-conversion system based on cascade modulators is proposed. After controlling the power and phase of the reference signal and photoelectrical conversion by a balanced photodetector (BPD), the intermediate frequency (IF) signal with self-interference cancellation is obtained. The proposed system will greatly reduce the cost of a full-duplex fiber communication system since it can solve the self-interference and frequency down-conversion at the same time. There is no electrical delay and attenuation, the proposed system can potentially reach the wider frequency band and the higher cancellation depth
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
