Flat optical frequency comb generation based on polarization modulator with RF frequency multiplication circuit and dual-parallel Mach-Zehnder modulator

A new approach to generate optical frequency comb (OFC) with good flatness, large side mode suppression ratio(SMSR) and tunable frequency spacing is proposed. The generator is composed of a polarization modulator (PolM) and a dual-parallel Mach-Zehnder modulator (DPMZM), and the PolM is modulated by a radio frequency(RF) frequency multiplication circuit. The theoretical analysis model of the proposed scheme is established. By adjusting the amplitude and frequency of the RF and the direct current(DC) bias voltage of modulators, 14-, 21- and 35-line OFCs with flatness value lower than 0.5 dB and SMSR value higher than 21 dB can be obtained easily. The stimulation results are in good agreement with the theoretical model.