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实验研究了一种基于相位调制器(PM)并级联强度调制器(IM)实现40 GHz毫米波传输正交频分复用(OFDM)信号的光纤无线通信(ROF)系统。在中心站,采用20 GHz的射频(RF)信号驱动PM,调节驱动信号的强度,使输出的信号经光纤布拉格光栅(FBG)滤除中心载波后再送入IM。2.5 Gbit/s的OFDM信号直接调制在光毫米波上,经过50 km标准的单模光纤(SSMF)传输到基站。在基站,光调制信号经光电转换器(PD)转换成电调制信号,再与RF信号混频,恢复出基带OFDM信号。实验结果表明,在无色散补偿、误码率(BER)为10-3的条件下,下行链路中2.5 Gbit/s的OFDM信号经光纤传输50 km后,其功率代价小于1 dB,而且信号的星座图依然较好。
An optical fiber wireless communication (ROF) system based on phase modulator (PM) and cascaded intensity modulator (IM) to realize 40 GHz millimeter wave transmission Orthogonal Frequency Division Multiplexing (OFDM) signal is experimentally studied. At the central station, a 20 GHz radio frequency (RF) signal is used to drive the PM to adjust the strength of the drive signal so that the output signal is filtered by a fiber Bragg grating (FBG) to remove the center carrier before being sent to IM. The 2.5 Gbit / s OFDM signal is directly modulated onto optical millimeter waves and transmitted over a 50 km standard single mode optical fiber (SSMF) to the base station. At the base station, the optical modulation signal is converted into an electrical modulated signal by a photoelectric converter (PD), and then mixed with the RF signal to recover the baseband OFDM signal. Experimental results show that the power cost of 2.5 Gbit / s OFDM signal in the downlink is 50 km and the power cost is less than 1 dB under the condition of 10-3 bit error rate (BER) without dispersion compensation. And the signal The constellation is still good.