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Sinc-shaped Nyquist pulses have wide applications in optical communications and microwave photonics. The quality of the generated Nyquist pulses has a significant effect on the overall performance of the communication system and the signal processing system. Generating high-quality Nyquist pulses with integrated silicon modulators is however still challenging due to the highly nonlinear response and fabrication-induced discrepancies of the device. We present a model for a silicon dual-parallel modulator with which the best possible quality of the generated optical frequency comb (OFC) and sinc-shaped Nyquist pulses can be obtained. In the model, the phase and amplitude deviations are taken into consideration. Device induced waveform and spectrum distortion can be well described. Based on the guidance of the model, a root-mean-square error of 2.8% is obtained between the experimentally generated signals and the ideal pulses, which proves the high accuracy of the model and its importance for high-quality Nyquist pulse generation.

We demonstrate nine-line optical frequency comb (OFC) and sinc-shaped Nyquist pulse generation based on two cascaded silicon Mach–Zehnder modulators. The OFC has a flatness of 1.83 dB, a frequency spacing of 5 GHz, and a corresponding Nyquist pulsewidth of ∼22 ps. Moreover, multi-wavelength operation and repetition rate tunability have also been demonstrated, which indicates the potential of our work to generate an on-chip high-speed pulse train demanded in optical communications and microwave photonics applications.

We demonstrate novel phase-coded microwave signal generation based on a two-segment single-drive push–pull silicon Mach–Zehnder modulator. The coding signal and the microwave frequency are each applied to one of the separate segments. The phase-coded microwave signal is generated by properly setting the working point of the modulator. The precise π phase shift is determined by the sign of the coding signal. Both theoretical analysis and experimental demonstration are performed to verify the concept. The modulator successfully generates a 10-GHz (20-GHz) phase-coded microwave signal with a 5-Gb/s (10-Gb/s) coding data rate and the measured pulse compression ratio is 133.0 (156.8).