实验研究了一种采用马赫曾德尔强度调制器和光交叉复用器(IL)产生58 GHz光载毫米波传输正交频分复用(OFDM)信号的波分复用光纤无线通信(WDM-ROF)系统。中心站的4路连续光波耦合后输入射频(RF)信号频率为29 GHz的强度调制器进行双边带(DSB)调制,再用另一个强度调制器将2.5 Gb/s的OFDM信号调制到DSB信号上。经20 km单模光纤(SMF)传输至基站,通过IL将中心载波和一阶边带分离。经可调谐光滤波器(TOF)滤取所需信道的一阶边带,由高速光电检测器产生58 GHz的电毫米波,利用相干解调恢复下行OFDM基带数据信号。实验结果表明,在无色散补偿和误码率为10-3的条件下,下行OFDM信号经光纤传输20 km后的功率代价小于0.5 dB,而且星座图依然清晰。

A wavelength division multiplexing radio-over-fiber (WDM-ROF) system to generate 58 GHz optical millimeter (mm)-wave with OFDM signal by using a Mach-Zehnder intensity modulator and an optical interleaver (IL) is experimentally investigated. In the central office,four channels continuous lightwaves are generated by a laser array,and they are modulated by a intensity modulator which is driven by a 29 GHz radio frequency (RF) signal to realize double sideband (DSB) modulation. 2.5 Gb/s OFDM signals are modulated on the DSB signals by another intensity modulator before they are transmitted to the base station over 20 km single mode fiber (SMF). In the base station,an optical IL is used to separated optical carriers and first order sidebands. The first sidebands of desired channel are selected by a tunable optical filter (TOF) and detected by a high speed optoelectronic detector to generate 58 GHz electrical mm-wave which is demodulated by coherent demodulation to retrieve downstream OFDM baseband signals. The experimental results show that the power penalty of the downstream OFDM signals transmitted over 20 km SMF-28 is less than 0.5 dB at the BER of 10-3 and without dispersion compensation,and the constellation figures are still clear.