实验研究了采用单个相位调制器(PM)产生毫米波的方案。该方案采用电混频器将射频(RF)信号与基带信号混频后再利用相位调制器产生双边带调制(DSB)信号, 经光纤传输到基站后用一个光交叉复用器(IL)分离一阶边带和中心载波, 一阶边带经过光电(O/E)检测器拍频产生两倍频于射频频率的毫米波, 而中心载波可以作为上行链路载波重新利用。理论分析了该毫米波的传输性能, 研究发现由于色散导致两个一阶边带时延不同, 码元的占空比会随着传输距离的增加而减小,将限制毫米波的最大传输距离; 实验中采用频率为20 GHz射频信号产生频率为40 GHz的毫米波, 速率为2.5 Gbit/s的非归零(NRZ)码作为下行链路数据, 经过20 km色散光纤传输后下行链路的功率代价为0.2 dBm。

A scheme of millimeter (mm)-wave generation utilizing one phase modulator (PM) has been proposed experimentally. To generate a mixing signal, the baseband signal is mixed with the radio frequency (RF) signal using an electric mixer. And the double-sideband (DSB) signal generated from phase modulator which is drived by the mixing signal is transmitted to base station along an optical fiber. The central carrier and the first-order sideband are separated by an optical interleaver (IL) at base station. The first-order sideband signals are beaten to generate the mm-wave with a double repetitive frequency of the RF signal when they are detected by an optical receiver, and the central optical carrier can be reused as carrier for uplink connection. The transmission performance of the mm-wave is analyzed. The duty cycle of the code decreases as the transmission distance increases because of the different delay of the first-order sidebands caused by fiber dispersion. And it limits the lagest transmission distance of the mm-wave. In the experiment, the 20 GHz RF signal generates 40 GHz mm-wave and 2.5 Gbit/s non-return-zero (NRZ) is carried by mm-wave. For downlink connection, the power penalty is 0.2 dBm after data transmit over 20 km dispersive fiber.