Bandwidth-limited, single longitudinal mode ultrashort optical pulse generation from a GaInAsP DFB diode laser at 1.54 μm was realized using the simplest method of strong rf modulation superimposed on the controlled dc bias current. A typical time-bandwidth product of 0.44, with a FWHM of about 37.5 ps at 500 MHz modulation, proves quasi-Lorentzian shaped optical pulses of excellent coherent character.