利用偏振分束器(PBS)和合束器(PBC)在不增加有源器件的基础上设计了一种双环路光电振荡器。该振荡器可以同时产生光、电两种输出。由于没有增加有源器件,可以避免附加电噪声的引入。此外,光载波在光域中是正交耦合,消除了随机干涉和拍噪声对振荡频率的影响。通过理论分析,双环结构的光电振荡器可以有效抑制每一单环路中起振的边模。经过实验对比,采用双环结构可以把边模抑制比提高30～70 dB。最后,利用该方案和普通商用器件得到了中心频率为12 GHz的振荡,测得边模抑制比为50～70 dB,相位噪声为-93 dBc/Hz at 10kHz,Q值达到1010。

Utilizing polarizing beam splitter (PBS) and polarizing beam combiner (PBC), a dual-loop optoelectronic oscillator (OEO) is designed without adding any active device. This oscillator can simultaneously produce optical and electrical output. No additional electronic noise can be introduced because of avoiding additional active devices. Furthermore, there is no signal frequency fluctuation and beat noise caused by interference and beating due to optical carrier orthogonally coupled in optical domain. According to the analysis of optoelectronic oscillator, dual-loop is able to effectively suppress the side modes in each single loop. Through experimental comparison, the side mode suppression ratio is improved by 30～70 dB. Finally, we demonstrate the free-running experimental result, which has high quality spectrum at 12 GHz with side mode suppression ratio 50～70 dB, phase noise of -93 dBc/Hz at 10 kHz from carrier and Q value of 1010.