Performance comparison of optical single-sideband modulation in RoF link

In this paper, three different single-sideband (SSB) modulation schemes, based on the dual drive Mach-Zehnder modulator (DD-MZM), IQ-MZM operating in push-push and push-pull modes respectively, are theoretically analyzed and validated by simulation in 60 GHz RoF link. The simulation results are well in accordance with the theoretical predictions. For the low-cost DD-MZM SSB scheme, a high optimal carrier signal power ratio (CSPR) results in low receiving sensitivity and the evident susceptibility of SSB form to the direct current (DC) drift are the main shortcomings. Instead, although suffering from the same high optimal CSPR issue for the push-push IQ-MZM SSB scheme, a wide tolerance to the DC drift as well as a low power loss of the modulator can be provided at the expense of cost. In addition, by adjusting the DC bias difference applied to the MZMs in conjunction with the Kramers-Kronig algorithm for signal-to-signal beating interference cancellation, the push-pull IQ-MZM SSB scheme can reduce the optimal CSPR by more than 3 dB and also provide 5 dB improvement in receiver sensitivity, as compared with the previous two SSB schemes. The analyses and results presented in this paper can provide a deep insight on improving the performance for the SSB RoF links.