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为了克服光纤无线(ROF)系统中色散对光载波抑制(OCS)调制光毫米波信号传输的影响,提出一种改进的OCS调制方案。使用双驱动马赫-曾德尔调制器(MZM),通过调整两路输入射频信号相位、基带信号增益和直流偏置电压将2.5Gbit/s数据信号仅调制到(OCS)信号的一个边带上传输。理论分析表明,与传统OCS调制光毫米波信号产生方案相比,本文方案解决了色度色散引起的码元走离问题,大大增加了传输距离。仿真实验结果表明,经过110km光纤传输后信号的眼图仍然十分清晰,在BER=10-10条件下,信号经过20、40和60km光纤传输后的功率代价分别为0.78、1.7和1.9dB。
In order to overcome the influence of dispersion on Optical Carrier Wave Suppression (OCS) modulated optical millimeter wave signal transmission in optical fiber wireless (ROF) system, an improved OCS modulation scheme is proposed. Using a dual-drive Mach-Zehnder modulator (MZM), a 2.5Gbit / s data signal is modulated onto only one sideband of the (OCS) signal by adjusting the two input RF signal phases, the baseband signal gain, and the DC bias voltage for transmission . The theoretical analysis shows that compared with the traditional OCS modulated optical millimeter wave signal generation scheme, this scheme solves the problem of the symbol wandering caused by chromatic dispersion and greatly increases the transmission distance. The simulation results show that the eye of the signal after the 110km optical fiber transmission is still clear. The power cost of the signal after passing through the 20, 40 and 60km optical fibers is 0.78, 1.7 and 1.9dB respectively under the condition of BER = 10-10.