A simple scheme of tunable parabolic pulses generation is proposed. Mathematically, a parabolic function is a quadratic function, which is equivalent to a sine-squared function when the independent variable is small enough. Since the transmissivity curve of Mach–Zehnder modulator is exactly a sine-squared function, bright parabolic pulse or dark parabolic pulse can be obtained that a linear drive signal with small voltage is used to map a center range of the peak or valley of the curve to the time domain. Starting from a sinusoidal signal, the second-order approximation triangular signal is simply obtained and used as a drive signal. By setting the bias point appropriately, parabolic pulses with the same or double frequency as the drive signals can be generated. Theoretical analysis and simulation are given. In the experiment, full-duty-cycle parabolic pulses at 2, 3, and 4 GHz and corresponding frequency-doubled pulses are obtained, which are consistent with the theoretical expectations.