Liu Pengcheng, Xie Zhanwu, Lin Dongdong, Lu Mengjia, Cheng Wei, Hu Guohua, Yun Binfeng, Cui Yiping
Opt Express. 2021 Oct 25;29(22):35377-35386. doi: 10.1364/OE.441780.
The ability to achieve low phase noise single-mode oscillation within an optoelectronic oscillator (OEO) is of fundamental importance. In the frequency-tunable OEO, the wide microwave photonic filter (MPF) bandwidth is detrimental to select single-mode among the large number of cavity modes, thus leading to low signal quality and spectral purity. Stable single-mode oscillation can be achieved in a large time delay OEO system by harnessing the mechanism from parity-time (PT) symmetry. Here, a PT-symmetric tunable OEO based on dual-wavelength and cascaded phase-shifted fiber gratings (PS-FBGs) in a single-loop is proposed and experimentally demonstrated. Combining the merits of wide frequency tuning of PS-FBG-based MPF and single mode selection completed by the PT-symmetric architecture of the OEO, where the gain and loss modes carried by dual-wavelengths to form two mutually coupled resonators in a single-loop, signals range from 1 GHz to 22 GHz with the low phase noise distributed in -122∼ -130 dBc/Hz at 10 kHz offset frequency are obtained in the experiment.
在光电振荡器（OEO）内实现低相位噪声单模振荡的能力至关重要。在频率可调谐OEO中，宽微波光子滤波器（MPF）带宽不利于在大量腔模中选择单模，从而导致信号质量和频谱纯度较低。通过利用奇偶时间（PT）对称机制，可在大时延OEO系统中实现稳定的单模振荡。在此，提出并通过实验证明了一种基于双波长和级联相移光纤光栅（PS-FBG）的单环PT对称可调谐OEO。结合基于PS-FBG的MPF宽频率调谐优点以及由OEO的PT对称架构完成的单模选择，其中双波长携带的增益和损耗模式在单环中形成两个相互耦合的谐振器，实验中获得了频率范围为1 GHz至22 GHz、在10 kHz偏移频率下具有-122∼ -130 dBc/Hz低相位噪声分布的信号。
