Filterless Radio-Over-Fiber System to Generate 40 and 80 GHz Millimeter-Wave

A filterless radio-over-fiber system to generate 40 and 80 GHz millimeter-wave was proposed by using two Mach-Zehnder modulators (MZMs). The two MZMs are biased at the maximum transmission point to suppress odd-order sidebands. By adjusting the modulation index of the two MZMs and the radio frequency drive signals, only the two 2nd and 4th order sidebands are retained. Subsequently, by adjusting the polarization direction to generate 40 and 80GHz frequency millimeter-wave signal. Detailed theoretical analyses and simulations are provided. The simulation results show that the 40 GHz millimeter-wave signal was obtained with 30 dB optical sideband suppression ratio (OSSR) and the 80 GHz millimeter-wave signal was obtained with 25 dB OSSR. Thanks to the higher OSSR, the generated MMW signal is not greatly affected by power fluctuations during transmission or frequency tuning. Furthermore, the effects of the modulation index, bias voltage and extinction ratios deviate from the ideal value on millimeter-wave performance are also analyzed and verified, showing the proposed scheme is relatively flexible from the limitation of filter fixed bandwidth and economical.