Generation of Flat Optical-Frequency Comb Using Cascaded Intensity and Phase Modulators

A scheme using one intensity modulator and two phase modulators driven directly by sinusoidal waveform to generate an optical-frequency comb (OFC) is experimentally demonstrated. It is relatively simple, where Bragg grating or specially tailored waveforms are not used. By setting the ratio of direct-current bias to half-wave voltage and phase shifts between sinusoidal waveform applied on the intensity and two phase modulators at appropriate values, 29 comb lines with spectral power variation less than 1.5 dB at 10 GHz are obtained. And the scheme has adjustability; a flat-top OFC with frequency spacing of 9.5-10 GHz is achieved.