Photonic Generation of Dual-Chirp Microwave Waveforms Based on a Tunable Optoelectronic Oscillator

We propose a photonic scheme to generate dual-chirp microwave waveforms based on a widely tunable optoelectronic oscillator (OEO) using a dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM). The upper DDMZM is properly biased to serve as a phase modulator and further constructs OEO loop to generate radio frequency (RF). The lower DDMZM injected by the combination of the RF and a single-chirp signal is utilized to generate a dual-chirp microwave waveform with an arbitrarily tunable central frequency. The RF from the OEO replaces external millimeter-wave source in our scheme, which improves the phase noise performance of RF in high-frequency range, alleviates the complexity of the system, and increases the possibility of integration. Dual-chirp microwave waveforms centered at 10 GHz with a bandwidths of 0.4 GHz and 1 GHz, and centered at 15 GHz with a bandwidth of 0.4 GHz are successfully generated. The proposed scheme is theoretically analyzed and experimentally demonstrated.