Reconfigurable Optical Frequency Comb and Nyquist Pulses Generation With Tunable Sensitivities

In this paper, a practical scheme to achieve reconfigurable optical frequency comb (OFC) and Nyquist pulses generation based on two cascaded Mach-Zehnder modulators and a polarization control structure is theoretically analyzed and verified by simulation. A rectangular-shaped OFC with evolvable comb lines (4 to 8) was obtained. Since there is no filter built in the structure, the turntable comb spacing is also an inherent feature of the OFC. These properties make the OFC can be used to produce high quality Nyquist pulses with flexible pulse duration (25.6ps similar to 14.4ps), duty cycle (11.5%similar to 20.5%) and repetition rate (4GHz similar to 40GHz). It is found that the sensitivity of the reconstruction process of the OFC and corresponding pulses is adjustable. By methods of mathematics, we expound the observed results and provide mathematical expressions about the relations between the optical sideband suppression ratio, modulation index, principle polarization direction and sensitivity. Moreover, a proof-of-concept experiment of the OFC generation is carried out and the results are consistent with the theoretical ones, which indicates the potential of our work to generate user-friendly reconfigurable OFC and Nyquist pulses demanded in microwave photonics, optical communications, all-optical sampling and light storage applications.