基于单边带调制的光毫米波产生及其传输特性研究

Investigation of generation and transmission performance of millimeter-wave based on single-sideband modulation

提出了一种新型单边带调制(SSB)产生光毫米波的全双工光纤无线通信(ROF)系统。利用射频(RF)信号驱动马赫-曾德尔调制器(MZM)产生偶数双边带信号,并通过技术基带信号调制到中心载波上,再与未被调制双边带的任一边带耦合产生光毫米波信号。理论分析发现,该毫米波的接收功率不会发生周期衰减。实验研究表明,经过50 km传输上行和下行链路信号的眼图仍旧是清晰张开的,说明本文系统能够有效克服光纤色散引起的衰落效应和传统单边带中信号码元的走离问题,适合于远距离传输。

A full-duplex radio-over-fiber（ROF） system with optical millimeter wave generation is proposed based on a novel single-sideband（SSB） by an external modulator.By properly biasing the intensity modulator,the repetitive frequency of the double-sideband（DSB） signal is four times of the RF singal frequency.After the central carrier was filtered by a FBG and modulated with baseband data at 2.5 Gb/s,it was recombined with the unmodulated second-order signal to generate optical millimeter wave by an optical coupler with a centain coupling coefficient and transmitted to the base station over a single-mode fiber.The central carrier and one of the second sidebands were beaten to generate the millimeter wave while the other second sideband was reused as carrier for uplink connection.The dispersion performance of the generated mm-wave was theoretically analyzed.The experimental results show that the eye diagrams of uplink and downlink singals are open clearly after transmission over 50 km fiber,and the system can reduce the fading effect caused by fiber dispersion and is immune to the walk-off of conventional single-sideband singal effectively.Therefore,it is suitable for long distance transmission.