Figure 5. Tunability of sinc-shaped Nyquist pulses using nine spectral lines.

Sinc-shaped Nyquist pulses measured using a 500-GHz optical sampling oscilloscope. The calculated waveforms (red-dashed lines) according to equation (10) are compared with the measured pulses (black straight lines) for different bandwidth conditions over 4 decades. Nyquist pulses are obtained from the generation of a rectangular frequency comb with nine phase-locked components spanning over a spectral width between 90 MHz and 90 GHz, using modulating frequencies (a) f₁=30 MHz and f₂=Δf=10 MHz, (b) f₁=300 MHz and f₂=Δf=100 MHz, (c) f₁=3 GHz and f₂=Δf=1 GHz, and (d) f₁=30 GHz and f₂=Δf=10 GHz. The maximum difference between measured pulses and theoretical ones remained in all cases below 1%.