A flat and broadband optical frequency comb with tunable bandwidth and frequency spacing

A flat and broadband optical frequency comb generator based on two cascaded intensity modulators is proposed and experimentally demonstrated. In this scheme, we first use even or odd harmonic sidebands to generate optical frequency comb, so the bandwidth can be improved. By adjusting the power of the microwave signals and the direct current bias applied to the modulators, a flat and broadband optical frequency comb can be achieved. The scheme is relatively simple and adjustable, where the frequencies spacing vary with microwave frequency applied on modulators. 15 and 20 comb lines with the comb flatness within 1 dB can be generated. The generated spectrums can meet the requirement of OFDM modulation, and can be used for high capacity optical transmission systems in the future.