Binary Programmable Optical Pulse Repetition-Rate Multiplication Based on Real-Time Fourier Transform

We propose and demonstrate a novel scheme to flexibly generate optical pulse trains with programmable repetition rates using newly designed binary modulation coefficients. The required coefficients are devised based on the principle of real-time Fourier transform (RTFT). By applying binary modulation with a Mach-Zehnder intensity modulator on a periodic pulse train prior to temporal Talbot processing, the multiplication factor can be easily manipulated. As a proof-of-concept, we have successfully produced pulse trains of different repetition rates reaching 250 GHz from a 10-GHz input, corresponding to a programmable multiplication factor of up to 25. The measured radio frequency (RF) spectra of the 20-GHz to 50-GHz output pulse trains exhibit higher than 44-dB subharmonic suppression ratio, indicating high-quality multiplied outputs. Our scheme shows resilience to the extinction ratio of the Mach-Zehnder intensity modulator. We also investigate the phase noise and timing jitter evolution of the multiplied optical pulses. Unlike the conventional Talbot processing approach, our programmable scheme shows a reduction of the timing jitter as the multiplication factor increases. The tolerances of our scheme to non-ideal factors such as bias drift and binary coefficient deviation are numerically analyzed. In addition to pulse repetition-rate multiplication, we demonstrate the versatility of our binary modulation approach in programmable generation of pulsed optical waveforms.