提出了一种基于偏振调制器(PolM)和Sagnac环级联的多调制格式微波信号的光学产生方案。理论分析了PolM在基带编码信号的驱动下产生偏振键控(PolSK)信号的基本原理, Sagnac环中嵌有两个马赫增德尔调制器(MZM), 分别对顺时针和逆时针传输的PolSK信号进行独立调制。通过合理调整两个MZM的驱动信号, 实现了幅移键控(ASK)、频移键控(FSK)和相移键控(PSK)微波信号的产生。在仿真实验中, 产生了比特率为2 Gbit/s的40 GHz ASK信号、20/40 GHz FSK信号和20 GHz PSK信号, 同时验证了比特率和载波频率的宽带可调谐性。Sagnac环结构提升了系统的稳定性, 并且针对每种调制格式的微波信号, 在不改变链路结构的情况下其比特率和载波频率都可以通过控制基带编码信号和MZM的射频驱动来进行独立且灵活的调谐。

An optical generation scheme of microwave signals with multiple modulation formats based on a polarization modulator(PolM) and a Sagnac loop was proposed. The PolM was driven by a baseband coding signal to generate a polarization shift keying(PolSK) signal and the generation principle was theoretically analyzed. Two Mach-Zehnder modulators(MZM) were embedded in the Sagnac loop to modulate the PolSK signal transmitted clockwise or counterclockwise, respectively. The outputs of amplitude shift keying(ASK), frequency shift keying(FSK) and phase shift keying(PSK) microwave signals were achieved by properly adjusting the driving signals of two MZMs. In the simulation work, a 40 GHz ASK signal, a 20/40 GHz FSK signal and a 20 GHz PSK signal with a bit rate of 2 Gbit/s were produced. In addition, the broadband tunability of the bit rate and carrier frequency was verified. The system stability was improved with Sagnac ring structure. Furthermore, without changing the link configuration, the bit rate and carrier frequency for each modulation format of microwave signals can be tuned flexibly and independently by controlling the baseband coding signal and the RF driven signals of two MZMs.