提出了一种基于级联马赫-曾德尔调制器(MZMs)倍频系数可调的相位编码信号光产生方法。该方法的系统核心器件为级联MZMs,通过合理选择两个MZMs的直流偏置电压和调制指数等参数,可任意选取±k(k=1,2,…,5)阶边带中的一组边带。通过可编程光滤波器滤除5阶以上的高阶边带,再结合相位调制,可产生载波2、4、6、8和10倍频的相位编码信号。该方法是通过改变施加在级联MZMs上的射频驱动信号幅度实现倍频系数调节,方案简洁灵活。通过仿真实验验证了利用4 GHz的微波信号源分别产生载频32 GHz和40 GHz的相位编码信号,从而实现了8和10倍频信号输出,且所生成的相位编码信号具有很好的脉冲压缩性能。

We propose a photonic approach to generate phase-coded signal with tunable frequency multiplication factor based on cascaded Mach-Zehnder modulators (MZMs). The key component in the system is the cascaded MZMs. We can select the ±k-order (k=1,2,…,5) sidebands by controlling the direct current(DC) bias voltage and modulation index of the two MZMs. We use programmable optical filter to filter the ±k-order (k>5) sidebands, and then combined with the phase modulation, can generate the phase-coded signal with frequency multiplication factors of 2, 4, 6, 8, and 10. In the proposed system, we can change the amplitude of the RF-driven signal applied to the cascaded MZMs to adjust the frequency multiplication factor by changing the amplitude of the RF driven signal of the cascaded MZMs. The scheme is more compact and flexible. The feasibility of this approach is demonstrated through a simulation experiment. The simulation results show that we can generate the phase-coded signals with frequencies of 32 GHz and 40 GHz using a 4 GHz microwave signal source. It means that we achieve the frequency multiplication factors of 8 and 10. Meanwhile, the pulse compression capability of the generated phase-coded signal is also demonstrated to be very well.