Microwave photonic frequency downconverter based on single sideband modulation

A microwave photonic frequency downconverter is proposed and experimentally demonstrated based on an integrated polarization division multiplexing dual-parallel Mach-Zehnder (PDM-DPMZM) modulator. The radio frequency (RF) and the local oscillator (LO) signals are feed to the modulator through two electrical 90 degrees hybrid couplers, respectively. The carrier suppress single sideband (CS-SSB) modulation can be achieved by adjusting the DC biases of the modulator. Then an intermediate frequency (IF) signal can be obtained by beating. The microwave photonic frequency downconversion link based on PDM-DPMZM is built. The result shows that both optical carrier sideband suppression ratio and sideband suppression ratio are over 20dB, and the spurious-free dynamic range achieves 98.0 dB.Hz(2/3). No extra mixing spurs interferes the interested IF signal owing to the CS-SSB modulation. Besides, the proposed method has good isolation between the RF signal and LO signal.