In this paper, we review a method to produce optical sinc-shaped Nyquist pulses with unprecedented quality. The method is based on the synthesis of a rectangular shaped and phase-locked frequency comb from a combination of intensity modulators. The result is a highly flexible pulse generator that can easily be integrated in already installed communication systems. All-optical pulse shaping methods for highest spectral efficiencies are attractive since high-bitrate spectrally efficient channels can be combined into multiple Tbit/s superchannels, enabling ultrahigh data transmission rates and a simultaneous ultrahigh spectral efficiency. Ideal sinc-shaped Nyquist pulses thus unlock the path towards minimal inter-symbol interference and no-guard band wavelength multiplexing. Here we will report on the generation, modulation and multiplexing of the sinc-shaped pulses obtained while using off-the-shelf components.