Photonic Generation of Triangular-Shaped Microwave Pulses Using SBS-Based Optical Carrier Processing

A photonic approach to generate triangular-shaped microwave pulses using stimulated Brillouin scattering (SBS)-based optical carrier processing is proposed and experimentally demonstrated. In the proposed approach, only odd-order optical sidebands are obtained by externally modulating the CW light wave using a Mach-Zehnder modulator (MZM) biased at the minimum-transmission-point (MITP). Then the suppressed optical carrier is recovered by the amplification effect from the SBS gain. After that, all negative-order optical sidebands are removed by using an optical filter. Through opto-electronic conversion in a photodetector (PD), the amplitude of the 1st-order electrical harmonic can be tuned just to be nine times of that of the 3rd-order one when the modulation index is specified as 1.51. Therefore the target pulse is generated and its repetition rate can be flexibly tuned by adjusting the frequency of the radio frequency (RF) signal applied to the MZM. According to the principle above, triangular-shaped microwave pulses with repetition rates of 5, 8, and 10 GHz are generated in our experiments, respectively, showing desired waveforms and excellent tunability.