Synchronization of Two Microwave Sources With Femtosecond-level Residual Timing Jitters Using a Microwave Photonic Phase Detector

A microwave photonic phase detector (MPPD) for simultaneous synchronization of two independent microwave sources to a single mode-locked laser (MLL) with femtosecond-level residual timing jitters is firstly proposed and experimentally demonstrated. A Sagnac loop is built based on a dual-polarization dual-drive Mach-Zehnder modulator (DP-DMZM). Each path consisting a branch of the modulator forms an MPPD due to its feature of polarization multiplexing. Thus, two dielectric resonator oscillators (DROs) can be synchronized simultanesously. A proof-of-concept experiment is carried out. Two independent DROs with frequencies of 8.0320 and 8.3332 GHz are synchronized to an MLL. The phase noises of the synchronized 8.0320-GHz signal are −109.79 and −135.14 dBc/Hz at the 1-kHz and 10-kHz offset frequencies, respectively, and those of the 8.3332-GHz signal are −106.87 and −133.86 dBc/Hz. The residual timing jitters of the two synchronized signals (integrated from 100 Hz to 1 MHz) are around 2.12 fs and 5.93 fs, respectively. The impact of the amplitude and phase imbalances of the driven signals to the DP-DMZM on the performance of the MPPD is investigated.