| Radio-Over-Fiber (ROF) technique, the integrated optical and wireless access system, has been considered cost-effective and reliable for the distribution of the future wireless access networks. When ROF technique is used for the distribution of wireless signals, optical mm-wave signal generation and distribution over fiber link are desired and considered a potential cost-effective solution. In this paper, at first the author analyzes operation principle of Mach-Zehnder (MZ) modulator, and deduces the theoretical formula for optical mm-wave generation based on MZ modulator. Secondly, this paper introduces a variety of mainstream techniques for optically generating mm-wave, and emphasizes the transmission performance of the optical mm-wave generation by using an external modulator based of DSB, SSB and OCS intensity modulation. Finally, a novel optical mm-wave double-sideband (DSB) modulation scheme which can be used in ROF transmission is proposed, the proposed scheme can transmit two mm-wave signals simultaneously. Theoretical study and numerical simulation show that the received millimeter-wave has no periodical power fading effect, and does not have the problem of the time shift of the code edges caused by fiber chromatic dispersion. The proposed modulation scheme can increase both the spectrum efficiency and the transmission distance of ROF systems. |
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