Simplified optical millimeter-wave generation configuration based on frequency octupling

Abstract

In this paper, a tunable, wideband, with simple configuration to generate frequency octupled millimeter (mm)-wave signal for radio-over-fiber systems is theoretically analyzed and experimentally demonstrated. The proposed system consists of two cascaded Mach–Zehnder modulators (MZMs). The first one is working at optical carrier suppression modulation that is used for the first-order optical harmonic generation. The second one is dual-parallel MZM which utilized the first-order optical harmonic to generate frequency octupled mm-wave signal. The experiments show that without any filter, a wideband frequency octupled optical mm-wave signals with the frequency varying from 4 to 80GHz and the undesired sideband suppression ratios of higher than 34dB can be obtained. The phase noise performance and the transmission performance of the radio-over-fiber downlink system are also demonstrated. The single-sideband phase noise of the generated 80GHz signal is −88dBc/Hz at 10kHz offset. The power penalty is less than 3dB at the bit error rate of 10−10 after 50km single-mode fiber transmission. Furthermore, it is proved to be valid that the proposed scheme is insensitive to the RF signal phase drift and the MZM bias drift, which demonstrates a relatively higher stability.