Optical frequency comb generation using two cascaded intensity modulators

A simple scheme based on two cascaded intensity modulators to generate a flat optical frequency comb (OFC) is proposed and experimentally demonstrated. By setting the two controllable parameters of the intensity modulation (RF amplitude and DC bias), five comb lines with a comb flatness within 0.6 dB are generated. When cascaded with another intensity modulator, 25 comb lines with a spectral power variation of less than 0.9 dB are obtained. The scheme, with a high unwanted-mode suppression ratio 13.1 dB and very low RF signals 0.58V(pi), is relatively simple, cost-efficient and adjustable, with the frequency interval of the OFC varying with the microwave frequency applied to the modulators.