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考虑到星间微波光子链路传输损耗大且多路微波信号之间交调干扰严重,利用前置光放大来提高链路的信号噪声失真比RSNDR。建立了两路输入前置光放大星间微波光子链路模型,推导出了RSNDR的解析表达式。通过优化马赫-曾德尔调制器的直流偏置相移,使得在给定输入射频信号功率条件下RSNDR最大,并进一步分析了前置光放大器参数对最优直流偏置相移和RSNDR的影响。仿真结果表明,前置光放大改变了影响RSNDR的主要因素,使信号放大的倍数大于噪声和三阶交调(IM3)放大的倍数,从而提高了链路的RSNDR。当前置光放大器增益为20dB、噪声系数为3dB时,最优的RSNDR比不加前置光放大器时提高24dB。前置光放大器增益和噪声系数对最优的RSNDR影响很大,而对最优的直流偏置相移几乎无影响。
Taking into account the large inter-satellite microwave photonic link transmission loss and interference between multiple microwave signals serious interference, the use of pre-optical amplifier to improve the link signal noise distortion ratio RSNDR. The microwave photonic chain model of two input preamplifier amplifiers was established and the analytical expression of RSNDR was deduced. By optimizing the DC offset phase shift of the Mach-Zehnder modulator, the RSNDR is maximized under given input RF signal power, and the influence of pre-amplifier parameters on the optimal DC offset phase shift and RSNDR is further analyzed. The simulation results show that the pre-amplification of light changes the main factors that affect RSNDR, which makes the signal amplification greater than the multiplication of noise and third-order intermodulation (IM3) amplification, which improves the RSNDR of the link. At present, when the gain of the optical amplifier is 20 dB and the noise figure is 3dB, the optimal RSNDR is increased by 24 dB compared with that without the optical amplifier. The gain and noise figure of the preamplifier have a significant effect on the optimal RSNDR but have little effect on the optimal DC offset phase shift.