20 GHz arbitrary radio-frequency waveform generator based on incoherent pulse shaping.

We demonstrate a new approach of photonically assisted radio-frequency (RF) waveform generation using a spectrally incoherent light source. The system is based on the so-called generalized frequency-to-time mapping operation. In this work, external modulation of the source is done by concatenating two electro-optic Mach-Zehnder modulators properly biased to achieve short pulse gates which allow for broad bandwidth electrical signals. Also, the spectral shaping stage is performed prior to O/E conversion. A detailed theoretical analysis demonstrates that even in this case the frequency-to-time mapping is preserved. The key is that the noise level is greatly reduced because the amplitude filter serves as noise rejecter. Experimental results show up to approximately 20 GHz electrical bandwidth signals using 10 Gb/s standard telecommunication equipment with the nice feature of repetition rate control on the generated electrical waveform.