Photonic generation of amplitude-and phase-modulated microwave signals with frequency and modulation bit-rate tunability

A photonic approach for the generation of an amplitude- and phase-modulated microwave signal with tun- able frequency and modulation bit-rate is proposed and demonstrated. Two coherent optical wavelengths are generated based on external modulation by biasing a Maeh Zehnder modulator （MZM） at the minimum transmission point to generate ±1-order optical sidebands while suppressing the optical carrier. The two sidebands are sent to a circulator and are then speetrally separated by a fiber Bragg grating notch filter. With one sideband being amplitude-modulated at another MZM and the other being phase-modulated at a phase modulator, a frequency-tunable amplitude- and phase-modulated microwave signal is generated by beating the two sidebands at a photodetector. The proposed technique is investigated theoretically and experimentally. As a result, a 20-GHz amplitude-modulated, 20-GHz phase-modulated, and 25-GHz amplitude- and phase-modulated microwave signals with tunable modulation bit-rate are experimentally generated.