提出了一种基于平面光波导谐振腔的可调谐光电振荡器.该振荡器中, 相位调制器串联光波导谐振腔, 取代了传统系统中的强度调制器、长光纤和滤波器.由于光学谐振腔对光子频率和相位敏感, 调节激光器改变输出光的波长, 不仅可以调制光的强度, 还可以对微波光子进行选频输出.当光子在波导腔中发生谐振时, 产生很强的延时特性, 可以取代传统系统中的长光纤.整个光电振荡器系统体积为长29.5 cm、宽21 cm、高7 cm.实验中, 改变0.1 pm的光子波长, 能够产生步长为12.5~35.5 MHz的调谐, 调谐范围达2 GHz, 且系统能够产生10 GHz的微波信号, 在中心频率为10 GHz处其相位噪声为－109.7 dBc/Hz@10 kHz.该研究为光电振荡器的小型化和实用化提供了一种新的思路.

GaAs-based polarization modulators (PolMs) exhibit the unique characteristic of simultaneous intensity and complementary phase modulation owing to the linear electro-optic (LEO) effect determined by crystallographic orientations of the device. In this paper, we reviewed the principle of operation, the design and fabrication flows of a GaAs-based PolM. Analytical models are established, from which the features of a PolM are derived and discussed in detail. The recent advances in PolM-based multifunctional systems, in particular the PolM-based optoelectronic oscillator (OEO) are demonstrated with an emphasis on the remarkable development of applications for frequency conversion, tunable microwave photonic filter (MPF), optical frequency comb (OFC), arbitrary waveform generation (AWG) and beamforming. Challenges in practical implementation of the PolM-based systems and their promising future are discussed as well.

This paper presents an introduction to the researches in microwave photonics based packages and its application, a 973 project (No. 2012CB315600), which focuses on addressing new requirements for millimeter wave (MMW) system to work with higher frequency, wider bandwidth, larger dynamic range and longer distance of signal distribution. Its key scientific problems, main research contents and objectives are briefed, and some latest achievements by the project team, including generation of linear frequency modulation wave (LFMW), tunable optoelectronic oscillator (OEO) with lower phase noise, reconfigurable filter with higher Q value, time delay line with wider frequency range, down conversion with gain, and local oscillator (LO) transmission with stable phase, are introduced briefly.

设计了一种利用微波光子滤波器(MPF)实现频率可调谐的光电振荡器(OEO)。该模型通过双驱动Mach-Zehnder调制器(DD-MZM)和啁啾光栅形成高Q值的MPF, 得出OEO的振荡频率是关于光源波长和DD-MZM直流偏置电压的函数, 通过对光源波长或DD-MZM偏置电压的调整, 可实现振荡频率调谐功能。同时, 在电域上, 利用RF耦合器和RF延时线形成两路具有延时差的反馈信号, 通过合并后反馈至DD-MZM, 从而有效地抑制边模。理论和仿真实验表明, 针对不同的调谐范围可实现粗调和微调的功能。

为了从高速OTDM(光时分复用) 信号中提取出支路时钟并实现解复用, 实现高速光信号与相对低速电信号之间的接口, 首次展示了一种基于商用的MZM(马赫-曾德调制器)和PolM(偏振调制器)级联的OEO(光电振荡器)实现从2×40 GBaud/s OTDM信号中提取支路时钟并同时解复用的实验方案。利用这种改进的OEO, 成功地从2×40 GBaud/s的OTDM DQPSK(差分四相相移键控)调制格式的高速光信号中提取出了40 GHz电时钟, 该时钟的相位噪声在10 kHz频偏处达到-98.62 dBc/Hz, 与微波源(Agilent Technologies, E8267D)的相位噪声质量几乎相同。这种OEO还同时实现了从OTDM信号中解复用出两个支路信号的功能, 即将160 Gbit/s的PRBS( 伪随机二进制序列) OTDM信号成功解复用为两路高质量的80 Gbit/s支路信号。