Photonic Generation of Dual-Chirp Microwave Pulses by Self-Heterodyne Optical Beating

Abstract

This paper reports photonic generation of linear dual-chirp microwave pulses in S and L-bands by directly modulating a DFB laser diode with low frequency electronics in a self-heterodyne scheme. The excitation current waveform which results in linear up- and down-chirped pulses in a self-heterodyne setup was calculated using the measured current-frequency transfer function of the DFB-LD. Polarization multiplexing was used to synchronize the up- and down-chirped pulses in a single dual-chirp microwave pulse. The calculated chirp linearity was experimentally verified, and a time-domain analysis was performed showing a slowly varying microwave phase within a pulse.