Photonic-assisted square waveform generation using a dual-parallel Mach–Zehnder modulator

A photonic approach to generating square waveforms using a single dual-parallel Mach–Zehnder modulator driven by a single-tone radio frequency signal is proposed and demonstrated. The two sub MZM are set to be biased at the minimum transmission point and the maximum transmission point, respectively. By simply adjusting the modulation index to have a proper value, optical intensity with expression corresponding to the Fourier expansion of a square waveform is obtained, and square waveforms will be generated. Neither an optical filter nor an electrical component of frequency multiplier or hybrid is needed to guarantee the simplicity and the wide working frequency range. A proof-of-concept experiment is taken. Both 1- and 4-GHz square waveforms fitting well with the ideal ones are successfully generated.