Flexible Nyquist Pulse Sequence Generation With Variable Bandwidth and Repetition Rate

The rectangular spectrum of sinc-shaped Nyquist pulses enables the encoding of data in a minimum spectral width. Sinc pulses can improve optical sampling devices, could enable the implementation of ideal rectangular microwave photonics filters, and can be used for all-optical signal processing, spectroscopy, and light storage. Recently, the generation of sinc-pulse sequences with extraordinary quality was shown by the utilization of cascaded modulators. However, the line width and repetition rate of the pulses is limited by the modulator bandwidth. Here, we present the nonrestricted generation of flexible Nyquist pulse sequences. Therefore, multiple single lines of a comb generator are extracted with optical filters and subsequently processed by cascaded modulators. In a first proof-of-concept experiment, we achieved almost ideally sinc-shaped Nyquist pulses with a bandwidth of 286 GHz, a pulse width of 3.5 ps, and a duty cycle of 2.2%. However, sinc-shaped Nyquist pulse sequences in the femtosecond range with terahertz bandwidths would be possible with the method.