Microwave Photonic Mixer Based on Polarization Rotation and Polarization-Dependent Modulation

A microwave photonic mixer capable of both amplitude and phase modulation is proposed and experimentally demonstrated. This scheme utilizes single-sideband modulation in dual-drive Mach-Zehnder modulator and polarization rotation in semiconductor optical amplifier to generate a pair of phase coherent optical carriers with different polarizations, while a polarization sensitive Mach-Zehnder intensity modulator (MZM) is used for modulating the IF signal onto one of the generated carrier. Both the optical and the electrical spectra are measured and show successful frequency mixing. By setting the bias point of the MZM at slightly different voltages, our scheme supports binary-phase-shift keying, on-off keying, and amplitude-shift keying modulations. Widely opened eye diagrams and clear waveforms are experimentally obtained for all modulations. Moreover, the proposed scheme does not have a hard limit on the supported lowest local oscillator frequency and no reconfiguration is needed when a frequency change in the local oscillator is required.