Microwave Photonic Downconversion With Improved Conversion Efficiency and SFDR

In this paper, we report a novel approach of microwave frequency downconversion with improved conversion efficiency and high dynamic range, using two different configuration schemes. The first proposed scheme is designed by using a dual-parallel dual-drive Mach-Zehnder modulator and the second one using dual-parallel dual-phase modulator. The radio frequency (RF) message signal and the local oscillator (LO) signal are feeding these two parallel connected modulators. By using a tight control of the system parameters, we have reported an effective optical carrier suppression, resulting in high conversion efficiency. We show that when the link is amplified, the relation between m(LO) and m(RF) plays a vital role and gives a high value of conversion efficiency, where key parameters lead to the LO and RF modulators modulation index. The conversion efficiency is improved by 5.72 dBm, compared with previously published work using DP-MZM, and 28.4 dBm, compared with the cascaded connected modulator. An experimental demonstration of a proof of concept is also carried out where the intermediate frequency to noise ratio of 69.5 dB is reported.