为提高光载无线系统传输容量,提出一种混合频相调制信号光学产生技术。利用保偏光纤布拉格光栅对不同输入偏振态响应不同的特性,将加载到信号偏振态的基带信息转换到输出波长上,并通过在接收端的外插拍频实现频率调制。同时通过光学相位调制将信息映射到拍频产生的微波信号上,最终产生混合频相调制信号。搭建基带传输式光载无线系统,验证了该信号产生方法的有效性。产生了码率为1 Gbit/s、频率为12.5 GHz/9.5 GHz的混合频相调制信号,该信号经过5 km光纤传输后由接收端解调。信号的时域波形及解调后信号眼图与星座图等结果证明了所产生的混合频相调制信号的可靠性。

In order to improve transmission capacity of radio over fiber system, a photonic generation method of hybrid frequency and phase shift keying (FPSK) signal is proposed. Based on various response characteristics of polarization maintaining fiber Bragg grating (PM-FBG), the baseband signal modulated onto the optical polarization is translated to output wavelength shift. Then frequency beating is implemented at the receiver to achieve frequency modulation. Meanwhile, an optical phase modulator is employed at the transmitter to map the phase information of the optical signal to the generated microwave signal. Finally, a hybrid FPSK signal is generated. The proposed method is experimentally demonstrated through a transmission test in a radio over fiber (RoF) system. A hybrid FPSK signal with 1-Gbit/s bit rate and 12.5-GHz/9.5-GHz frequency is generated and modulated by the receiver after transmitting a 5-km fiber. The results of temporal waveform, the eye-diagram and constellation diagram after demodulation verify the effectiveness of the proposed scheme.