An approach for frequency division of an optical pulse train (OPT) based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. When the OPT is injected into the OEO, a microwave signal with a frequency equaling fractional multiples of the repetition rate of the OPT is generated. This signal is then fed back to the OEO, maintaining its oscillation, while simultaneously serving as the control signal of a Mach–Zehnder modulator (MZM) in the OEO. The MZM acts as an optical switch, permitting specific pulses to pass through while blocking others. As a result, the repetition rate of the OPT is manipulated. A proof-of-concept experiment is carried out. Frequency division factors of 2 and 3 are successfully achieved. The phase noises of the OPT before and after the frequency division are investigated. Compared to previously reported systems, no external microwave source and sophisticated synchronization structure are needed.

High accuracy and time resolution optical transfer delay (OTD) measurement is highly desired in many multi-path applications, such as optical true-time-delay-based array systems and distributed optical sensors. However, the time resolution is usually limited by the frequency range of the probe signal in frequency-multiplexed OTD measurement techniques. Here, we proposed a time-resolution enhanced OTD measurement method based on incoherent optical frequency domain reflectometry (I-OFDR), where an adaptive filter is designed to suppress the spectral leakage from other paths to break the resolution limitation. A weighted least square (WLS) cost function is first established, and then an iteration approach is used to minimize the cost function. Finally, the appropriate filter parameter is obtained according to the convergence results. In a proof-of-concept experiment, the time-domain response of two optical links with a length difference of 900 ps is successfully estimated by applying a probe signal with a bandwidth of 400 MHz. The time resolution is improved by 2.78 times compared to the theoretical resolution limit of the inverse discrete Fourier transform (iDFT) algorithm. In addition, the OTD measurement error is below ±0.8ps. The proposed algorithm provides a novel way to improve the measurement resolution without applying a probe signal with a large bandwidth, avoiding measurement errors induced by the dispersion effect.

基于硅基铌酸锂薄膜（Lithium Niobate on insulator，LNOI）材料平台，设计并制备了高速电光开关芯片，并实现了芯片的光纤耦合、管壳封装和性能测试。测试结果表明，该高速电光开关器件的开关速度达到13.4 ns，消光比达到31.8 dB。研究工作对未来研制光学延时芯片和波束形成网络芯片具有重要的支撑意义。

A broadband instantaneous multi-frequency measurement system based on chirped pulse compression, which potentially has a sub-megahertz (MHz) accuracy and a hundred-gigahertz (GHz) measurement range, is demonstrated. A signal-under-test (SUT) is converted into a carrier-suppressed double-sideband (CS-DSB) signal, which is then combined with an optical linearly frequency-modulated signal having the sweeping range covering the +1st-order sideband of the CS-DSB signal. With photodetection, low-pass filtering, and pulse compression, accurate frequencies of the SUT are obtained via locating the correlation peaks. In the experiment, single- and multi-frequency measurements with a measurement range from 3 to 18 GHz and a measurement accuracy of <±100 MHz are achieved.

微波光子学是一门融合了微波技术和光子技术的交叉学科，是研究光波和微波在媒质中的相互作用以及在光频域实现微波信号的产生、处理、传输及接收的微波光波融合系统。由于现有的微波光子系统大多由分立器件组成，在体积、功耗、稳定性、成本等方面仍有待提升，因此集成化是微波光子技术发展的必然趋势。文中探讨了微波光子集成技术面临的主要科学与技术问题，总结了该技术的发展现状和前沿研究进展，并对其未来发展前景进行了展望。

提出了一种由光生本振单元和波长分离调制单元组成的微波光子混频方法，并在绝缘体上硅材料上设计实现了上述波长分离调制芯片。该芯片集成了硅基相位调制器、微环滤波器、光电探测器、光耦合器和光栅耦合器。实验搭建了基于该波长分离调制芯片的微波光子次谐波混频系统，结果表明，该微波光子混频器可以将6~16 GHz的RF信号变频到33~23 GHz。此外，针对实验系统中残留的混频杂散，分别提出了增加微环滤波器抑制比降低泄露光生本振强度和引入光移相器修正泄漏光生本振相位两种解决方案。通过仿真验证可知，引入光移相器的方法更为简单，更适合于光子集成芯片。

微波光子雷达利用光子学方法实现雷达信号的产生与处理，具有突出的宽带工作能力，能显著提升雷达距离分辨率。为了提升雷达角度分辨能力并实现灵活波束控制，将微波光子雷达技术与阵列技术相结合是必然的发展趋势。目前研究较多的宽带阵列雷达采用光真延时技术克服宽带波束倾斜问题，通常面临复杂度高、灵活性差、延时精度有限等问题。近年来，基于微波光子倍频与去斜接收的宽带雷达收发架构得到了广泛关注，基于此技术构建的阵列雷达，在实现宽带工作的同时具备实时数字补偿与处理功能，为宽带阵列雷达的发展提供了新的思路。文中针对作者在此方面的最新研究进展进行了综述，在阐明基于微波光子倍频与去斜接收实现宽带雷达收发机理的基础上，介绍了构建宽带相控阵雷达的方法以及实现数字波束扫描与成像的性能。然后，将阵列形式扩展至多输入多输出（MIMO）形式，介绍了基于光波分复用技术实现宽带微波光子MIMO雷达的方法，并分析了微波光子MIMO雷达在目标探测与成像方面的性能。

We propose a photonics-assisted equivalent frequency sampling (EFS) method to analyze the instantaneous frequency of broadband linearly frequency modulated (LFM) microwave signals. The proposed EFS method is implemented by a photonic scanning receiver, which is operated with a frequency scanning rate slightly different from the repetition rate of the LFM signals. Compared with the broadband LFM signal analysis based on temporal sampling, the proposed method avoids the use of high-speed analog to digital converters, and the instantaneous frequency acquisition realized by frequency-to-time mapping is also simplified since real-time Fourier transformation is not required. Feasibility of the proposed method is verified through an experiment, in which frequency analysis of Kα-band LFM signals with a bandwidth up to 3 GHz is demonstrated with a moderate sampling rate of 100 MSa/s. The proposed method is highly demanded for analyzing the instantaneous frequency of broadband LFM signals used in radar and electronic warfare systems.