Photonic generation of dual-band dual-chirp waveforms with a programmable duty cycle and immunity to power fading

A photonic approach for generating dual-band dual-chirp waveforms with a programmable duty cycle based on a dual-drive Mach-Zehnder modulator (DDMZM) is proposed and experimentally demonstrated. By simultaneously applying a digital switching code, a predefined radio frequency (RF) signal, and a baseband chirped signal into the RF input ports of the DDMZM, dual-band dual-chirp signals with upconverted center frequencies are achieved, and their duty cycle can be fast switched. The switching speed is directly determined by the bit rate of the input code. Moreover, by appropriately adjusting the bias voltages, the generated signals can be anti-dispersion transmitted. Full experimental verification on the generation and anti-dispersion transmission of dual-band dual-chirp waveforms centered at 4.5 and 7.5 GHz over 10 or 20 km standard single-mode fibers with programmable duty cycle switching among 20%, 40%, 60%, and 80% is successfully carried out. The proposed approach features simple configuration, programmable switching capability, and immunity to power fading, which are highly desired in multifunction radar networks with optical fiber-based transmission.