基于双光学频梳的超宽带射频信号信道化合成技术研究(特邀)

随着现代通信系统的发展,宽带和高频微波射频信号在雷达,通信和信号处理等领域的应用越来越广泛。基于微波光子信道化技术,文中通过两个自由频谱范围不同的光学频梳,实现了超宽带射频信号的信道化合成。在信道化合成系统中,多个独立的窄带信号输入各个信道进行上变频,并在多外差探测中被重组成为一个具有连续频谱的宽带射频信号。在多外差探测中,干扰抑制技术的使用提高了合成射频信号可达到的最高频率。在实验中,合成了一个覆盖频率范围8.4~12.4 GHz,瞬时带宽为4 GHz的宽带射频信号。实验结果显示,干扰的抑制率达到了21 dB,表明干扰抑制技术的使用提高了输出信号的最高频率的同时有效地提高了频谱利用率。

A Review on Fiber Lasers

After a half century of development, fiber laser has evolved from a concept to a great family penetrating into various fields of applications. This paper reviews the history and current development of fiber lasers, with topics covering both continuous wave and short pulse fiber lasers. Important issues such as the major rare earth dopants, fiber laser brightness, polarization effects, clad pumping technology, beam combination, mode locking and pulse shaping are discussed in this paper.

Dual-Wavelength Linearization of Radio-over-Fiber Link for Broadband Access and Ubiquitous Sensing

Radio-over-Fiber （RoF） technologies have been considered to be a promising solution to broadband access and ubiquitous sensing. We present a novel approach using dual-wavelength lights to suppress the nonlinear intermodulation distortion in intensity-modulated RoF link both theoretically and experimentally. The system we proposed rminly consists of two Laser Diodes （LDs） at different wavelengths, a commercial available Mach-Zehnder Modulator （MZM） and a Photo Detector （PD）. More than 25 dB suppression of the Third-order Interrnodulation Distortion （IMD3） is achieved by adjusting the wavelength and opti- cal power of the laser. Besides, the output of the MZM is then sent to the photodetector via a single fiber, which simplifies the system complexity for distrbution of RF signals over long distances.

Broadband photonic radio frequency(RF) channelization based on coherent optical frequency combs and polarization I/Q demodulation

In this work,we analyze and demonstrate a novel photonic-assisted broadband and high-resolution radio frequency(RF) channelization scheme based on dual coherent optical frequency combs(OFCs),regular optical de-muxes,and polarization I/Q demodulators in theory and experiment.The use of two coherent combs avoids precise optical alignment,and a numerical filter in digital signal processor(DSP) enables an ideal rectangular frequency response in each channel without any ultra-narrow optical filters.Besides,due to the use of polarization I/Q demodulation,ambiguous frequency estimate in direct detection can be avoided and the amplitude,phase mismatch in traditional I/Q demodulation can be mitigated.In experiment,we use two coherent OFCs with the free spectrum range(FSR) of about 40 GHz to demonstrate the channelization scheme with seven channels,500 MHz channel spacing and frequency coverage from 3.75 GHz to 7.25 GHz.The input RF tones are accurately down-converted to an intermediate frequency(IF) with a maximum frequency error of 110 kHz.Meanwhile,crosstalk and spurious free dynamic range(SFDR) of the scheme are also discussed.

Preface

Owing to the fast economic growing and the concern over greenhouse gases and air pollution, the development of nuclear energy is one important option to meet the expanded energy consumption in our future. To achieve that goal, continuing and reliable supplies of uranium are critical to future nuclear power projects. As is well known, global terrestrial reserves of uranium are limited and the deposits in China are relatively small.

新型光电振荡器(特邀)

光电振荡器是拥有闭合光电反馈回路的微波光子信号源。借助微波光子学大带宽、低损耗等优势,光电振荡器可实现高中心频率、超低相位噪声的微波信号产生,从而克服传统电学信号源面临的频率和相位噪声瓶颈,应用于雷达、通信、测量和电子对抗等现代电子信息系统。综述近些年来涌现的新型光电振荡器,介绍可实现无滤波器单模振荡的宇称-时间对称光电振荡器、快速扫频的傅里叶域锁模光电振荡器、参量锁相的光电参量振荡器、频率随机变化的宽带随机光电振荡器、自发跳频的孤子光电振荡器、脉冲型的主动和被动锁模光电振荡器以及小型化的集成光电振荡器等,并探讨这些新型光电振荡器的应用和未来发展趋势。