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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 WDM-based optical fiber wireless communication system using Mach-Zehnder intensity modulator and optical interleaver (IL) to generate 58 GHz optical millimeter-wave transmission Orthogonal Frequency Division Multiplexing (OFDM) ROF) system. The central station’s 4-way CW light is coupled to an intensity modulator with an RF signal frequency of 29 GHz for double-sideband (DSB) modulation and a second intensity modulator to modulate a 2.5 Gb / s OFDM signal into a DSB signal on. Transmitted to the base station via 20 km single-mode optical fiber (SMF), separating the center carrier from the first-order sideband by IL. The first-order sideband of the desired channel is filtered by a tunable optical filter (TOF), a high-speed photodetector generates an electric millimeter wave of 58 GHz, and the coherent demodulation is used to recover the downlink OFDM baseband data signal. Experimental results show that the power cost of downlink OFDM signal after optical fiber transmission is less than 0.5 dB without chromatic dispersion compensation and bit error rate of 10-3, and the constellation map is still clear.