We experimentally demonstrated a novel structure for generating an optical frequency comb source for multicarrier modulation in an optical transmission system. In the proposed scheme, the integration of an electroabsorption-modulated laser cascaded with a phase modulator is employed, both of which are driven and synchronized via a common sinusoidal radio frequency signal. The optimal operating range defined as a spectral flatness with less than 3-dB power fluctuation can be obtained through numerical simulation. Using the proposed scheme, we can achieve 10 flat-topped and frequency-locked optical carriers with a 12.5-GHz frequency spacing. On–off-keying intensity-modulated signals with 3.125 and 12.5  Gb  /  s are transmitted error-free over 20 km standard single-mode fiber utilizing the proposed optical frequency comb source for an optical wavelength-division multiplexing transmission system.