Analysis of optical arbitrary waveform generation based on time-domain synthesis in a dual-parallel Mach–Zehnder modulator

Abstract

A photonic-assisted microwave arbitrary waveform generator is theoretically analyzed and verified by simulation. The basic principle of the generator is synthesis of optical field envelops. By using a sinusoidal signal to modulate a CW via a dual-parallel Mach–Zehnder (DP-MZM), square-shaped waveforms are directly generated firstly, whose envelops or harmonic power ratios are able to be modified by changing the RF driving voltage. When two identical square-shaped pulses with harmonics power ratio (9:1) between the 1st- and the 3rd-order components suffer a differential envelope phase shift (π/2), the superposition of these envelops contributes to a triangular-shaped waveform. Similarly, we generate flat-top waveform and Gaussian waveforms by properly setting the bias drifts of DP-MZM, time delay of the tunable time delay line, and modulation index. As DP-MZM is a key component in our proposal, we discuss the influence of the bias drifts on the generated waveforms, which make the scheme more practical.