A scheme of dual-loop optoelectronic oscillator (OEO) based on a directly modulated distributed feedback (DFB) laser is proposed and experimentally demonstrated. In the proposed scheme, thanks to the DFB laser with enough output optical power utilized as an optical source and a modulator at the same time, high-performance microwave signals are generated without external modulator and erbium-doped fiber amplifier (EDFA). A theoretical model based on the control theory is detailed to assess the single sideband (SSB) phase noise performance of the dual-loop OEO. The laser frequency noise under small-signal direct modulation is proposed and introduced to make the phase noise model more complete for the first time. According to the theoretical analysis, the close-in (<1 MHz) SSB phase noise floor of the dual-loop OEO is dominated by the flicker noise when the offset frequency is below 10 kHz, and determined by the laser’s relative intensity noise (RIN) when the offset frequency is beyond 10 kHz. Microwave signals with the frequency tuned from 8 to 12 GHz and 3-dB linewidth less than 100 Hz are realized. The side mode suppression ratio (SMSR) of the generated microwave signals are measured to be 55 dB based on the dual-loop configuration. Meanwhile, within the whole frequency tuning range, the SSB phase noises of about −125 dBc/Hz at 10 kHz offset frequency are obtained. The experimental results of the SSB phase noise agree very well with the simulation results based on the theoretical model.

提出了一种基于直接调制分布式反馈（DFB）激光器的双环光电振荡器（OEO）方案，并进行了实验验证。在提出的方案中，由于同时具有足够输出光功率的DFB激光器用作光源和调制器，因此无需外部调制器和掺光纤放大器（EDFA）即可生成高性能微波信号。详细介绍了基于控制理论的理论模型，以评估双环OEO的单边带（SSB）相位噪声性能。提出并引入了小信号直接调制下的激光频率噪声，首次使相位噪声模型更加完整。根据理论分析，近距离（< 1 MHz）当偏移频率低于10 kHz时，双回路OEO的SSB相位本底噪声主要由闪烁噪声决定，而当偏移频率超过10 kHz时，则由激光器的相对强度噪声（RIN）确定。实现了频率从8到12 GHz调谐且线宽小于100 Hz的3-dB的微波信号。基于双回路配置，生成的微波信号的边模抑制比（SMSR）被测量为55 dB。同时，在整个频率调谐范围内，在10 kHz偏移频率下可获得约-125 dBc / Hz的SSB相位噪声。SSB相位噪声的实验结果与基于理论模型的仿真结果非常吻合。当偏移频率超过10 kHz时，由激光器的相对强度噪声（RIN）决定。实现了频率从8到12 GHz调谐且线宽小于100 Hz的3-dB的微波信号。基于双回路配置，生成的微波信号的边模抑制比（SMSR）被测量为55 dB。同时，在整个频率调谐范围内，在10 kHz偏移频率下可获得约-125 dBc / Hz的SSB相位噪声。SSB相位噪声的实验结果与基于理论模型的仿真结果非常吻合。当偏移频率超过10 kHz时，由激光器的相对强度噪声（RIN）决定。实现了频率从8到12 GHz调谐且线宽小于100 Hz的3-dB的微波信号。基于双回路配置，生成的微波信号的边模抑制比（SMSR）被测量为55 dB。同时，在整个频率调谐范围内，在10 kHz偏移频率下可获得约-125 dBc / Hz的SSB相位噪声。SSB相位噪声的实验结果与基于理论模型的仿真结果非常吻合。基于双回路配置，生成的微波信号的边模抑制比（SMSR）被测量为55 dB。同时，在整个频率调谐范围内，在10 kHz偏移频率下可获得约-125 dBc / Hz的SSB相位噪声。SSB相位噪声的实验结果与基于理论模型的仿真结果非常吻合。基于双回路配置，生成的微波信号的边模抑制比（SMSR）被测量为55 dB。同时，在整个频率调谐范围内，在10 kHz偏移频率下可获得约-125 dBc / Hz的SSB相位噪声。SSB相位噪声的实验结果与基于理论模型的仿真结果非常吻合。