提出了应用于光纤无线通信系统中一种改进的双边带调制产生光毫米波方案。在中心站采用强度调制将射频信号调制到光载波上产生一个双边带信号,滤掉中心载波后,利用光交叉复用器把双边带信号的上下边带模分开,将数据速率为2.5 Gbit/s的基带信号调制到下边带模后,再与未调信号耦合后产生光毫米波,然后通过单模光纤传输至基站,在基站经过光电转换后产生电毫米波信号。从理论上对该毫米波的色散特性进行了分析,发现毫米波的接收功率不会周期的衰减。同时通过实验研究表明, 下行链路信号通过光纤能传输50 km而不需要色散补偿,功率代价小于1 dBm。因此,该方法产生的光毫米波能有效克服光纤色散引起的信号时延而导致的基带信号退化,适合于远距离传输。

A novel scheme for optical millimeter-wave generation with double-sideband (DSB) modulation by external modulator in a radio-over-fiber (ROF) system was proposed. At the central station, a CW lightwave was intensity-modulated by the RF signal to generate DSB signal. After the pure optical carrier was filtered, an optical interleaver was employed to separate the spectrum of the upper sideband and the lower sideband of the generated DSB signal. After the lower sideband signal was modulated with a baseband data at 2.5 Gbit/s, it was recombined with the unmodulated signal to generate optical millimeter wave, and then transmitted to the base station over single-mode fiber (SMF). In the base station, the electrical millimeter wave signal was generated by O/E conversion. The dispersion performance of the generated mm-wave is theoretically analysed, it can immune the fading effect. The experimental results show that the downlink data signals can transmit over 50 km fiber without dispersion compensation, and the power penalty is less than 1 dBm. So the generated optical millimeter wave by proposed method can effectively reduce baseband signal degeneration caused by the time shift of the code edges because of fiber dispersion, it is suitable for long distance transmission.