Theoretical analysis of high-quality multicarrier generator based on double complementary re-circulating frequency shifter

Due to the inefficiency of the traditional multicarrier generation system, a double-band re-circulating frequency shifting (RFS) structure based on DP-MZM (Dual Parallel Mach–Zehnder modulator) is proposed. Contrary to the conventional single-sideband re-circulating frequency shifting architecture, the efficiency of this structure is doubled, while the cost is reduced to nearly half. The transfer function and output properties of double-band RFS are theoretically analyzed in detail. The proposed novel structure for large and ideal signal conditions is simulated. Furthermore, the influence of ASE noise from EDFA is discussed in detail. In the simulation, to get high quality multi-carriers, the RF drive voltage is V _pp =0.18V _π , the frequency spacing fs is 12.5 GHz, and the half-wave voltage of both two Mach–Zehnder modulators is kept at V _π =4V. The results show that when the RFS loop is set at 30, 50 and 100 times, the number of 60, 100 and 200 stable carriers with a frequency spacing of 12.5 GHz are obtained with the flatness of 0.6026dB, 0.7769dB, 1.148dB separately. The carrier-to-noise ratio is calculated as around 40dB. Compared with the traditional single-sideband structure, the proposed scheme has high efficiency, high flatness, large carrier-to-noise ratio and lower RF driving voltage, making it a novel promising technique for future perabit multicarrier transmission.