Proposed Scheme for Ultra-Flat Optical Frequency Comb Generation Based on Dual-Drive Mach–Zehnder Modulators and Bidirectional Recirculating Frequency Shifting in Single Loop

Recirculating frequency shifting has attracted much attention for its advantages in the generation of flexible and high-quality optical comb. A new scheme ultra-flat comb system based on single-loop bidirectional recirculating shift is proposed studied this paper. The employs two pairs dual-drive Mach–Zehnder modulators several polarization devices. Compared with method unidirectional recirculation shift, under same cycles, number lines generated by doubled, combs have less noise accumulation better flatness. theoretical model established, verified software simulation. 111-line spacing 12.5 GHz, flatness 0.76 dB, signal-to-noise ratio 27.39 dB was obtained adopting scheme.