A Triple-Frequency Microwave Photonic Link Based On A Polarization-Multiplexing Dual-Parallel Mach-Zehnder Modulator

A triple-frequency microwave photonic link is proposed based on a polarization-multiplexing dual-parallel Mach-Zehnder modulator (PM-DPMZM). The lower sub-DPMZM is biased at the maximum transmission point to obtain the 2nd-order RF sidebands. Meanwhile, the RF signal modulates the upper sub-DPMZM through an electrical 90 degrees hybrid coupler. The upper sub-DPMZM works at the carrier-suppressed single-sideband (CS-SSB) modulation to obtain the +1st order RF sideband. An optical band pass filter is used to filter out the +2nd-order RF sideband, and only the +1st-order and -2nd-order RF sidebands are output for the frequency beating at a photodetector (PD). The frequency triple signal of 3 omega(RF) is obtained correspondingly. The experimental link is built. The results show that the RF signal from 8 to 12 GHz is tripled, and frequency tripled signal at 24 to 36 GHz is acquired. The minimal spur suppression ratio of triple-frequency signal is 20dB. A relatively low-frequency signal can be used to generate a high-frequency signal with well quality by this triple-frequency link. The proposed method can be applied in various microwave photonic transmitting systems.