两路输入前置光放大星间微波光子链路优化

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。

Optimization of Optically Preamplified Inter-Satellite Microwave Photonics Links with Two Radio-Frequency Signals Input

An optical preamplifier is utilized to improve the signal-to-noise and distortion ratio RSNDR of inter-satellite microwave photonics links considering the large signal losses in distant propagation and serious deterioration caused by inter-modulation distortion. An optically preamplified inter-satellite microwave photonics links model with two radio-frequency (RF) signals input is established and an analytical expression of RSNDR is derived. The direct current (DC) bias phase shift of modulator can be optimized so as to maximize the RSNDR given the desired input RF signal power, and the effects of the optical preamplifier parameters on the optimum DC bias phase shift and RSNDR are also examined. Simulation results show that the most limitative factors degrading the RSNDR are changed, and the fundamental power is seen to increase more compared with the power of third-order intermodulation (IM3) plus noise due to optical preamplifier. Thus, RSNDR can be improved with respect to the case of non-optical preamplifier. For the preamplifier gain of 20 dB and noise figure of 3 dB, an improvement of about 24 dB in optimum RSNDR is accessible. The optimum DC bias phase shift is found to be insensitive to the preamplifier gain and noise figure while the optimum RSNDR is sensitive to the preamplifier gain and noise figure.