中国激光
2021, 48(15): 1501000
Author Affiliations
Abstract
1 Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
2 FiberHome Telecommunication Technologies Co., Ltd., Wuhan 430074, China
We present the investigation on deformation of orbital angular momentum (OAM) modes in bending ring-core fibers (RCFs) with different structure sizes through numerical and experimental studies. The effective refractive index differences of even and odd fiber eigenmodes, which constitute OAM±1,1 modes, induced by RCF bending and their impacts on the OAM±1,1 mode intensity distributions are analyzed. Bending experiments are also carried out on three different RCFs, and the results match well with simulation values. It is found that RCFs with smaller inner and outer radii show preferable tolerance to the fiber bending.
050.4865 Optical vortices 060.2270 Fiber characterization 060.2310 Fiber optics Chinese Optics Letters
2017, 15(3): 030501
Author Affiliations
Abstract
Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
A highly linear W-band receiver front-end based on higher-order optical sideband (OSB) processing is proposed and experimentally demonstrated. Two-tone analysis shows that by manipulating higher-order OSBs, the third-order intermodulation distortion (IMD3) introduced by optoelectronic components (mainly modulators) in the receiver front-end can be further suppressed, and a 9 dB improvement of the ratio of the fundamental and IMD3 can be attained. In the experiment, the spurious-free dynamic range of the W-band receiver front-end is up to 122.1 dB·Hz2/3, with improvement by 9 dB compared with that of only processing the five OSBs.
060.2360 Fiber optics links and subsystems 060.5625 Radio frequency photonics 130.4310 Nonlinear Chinese Optics Letters
2017, 15(5): 050603
Author Affiliations
Abstract
Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
A finite impulse-response microwave photonic filter is typically achieved based on spectrum-shaped optical frequency combs and a dispersive element. We propose an analytical model to describe the amplitude responses of the sidelobes. The model shows that the sidelobe suppression ratio is limited by the spectrum structure of the optical combs. By taking Gaussian-profiled combs as an example, it is both theoretically and experimentally proved that the suppression ratio can be improved by optimizing the spectral power range, which is defined as the ratio of the maximum tap weight to the minimum tap weight.
060.5625 Radio frequency photonics 070.2615 Frequency filtering 350.4010 Microwaves Chinese Optics Letters
2016, 14(6): 060601
清华大学电子工程系, 清华信息科学与技术国家实验室, 北京 100084
提出并实现了一种用光纤色散压缩脉冲为载波的上变频射频光载系统。该系统把传统的连续光载波替换为频率啁啾脉冲，利用传输光纤色散压缩脉冲宽度，增强谐波分量，使脉冲载波上的信号在接收端转换到脉冲高次谐波上，从而实现了远端上变频。该方法的特点是用低频本振就可实现高频微波信号的产生，发射端无需电倍频器、混频器，接收端只需用滤波器选择所需频率信号，系统结构简单。应用该方法实现了2 Gbit/s信号经60 km普通单模光纤传输后远端上变频到16 GHz、经过5.4 m无线传输后误码率低于10-8的射频光载系统，系统中只有一个光功率放大器，无光在线和预放大以及光滤波器和色散补偿。
光通信 上变频 脉冲压缩 模拟链路 光载无线通信 光纤色散 带通滤波
清华大学 电子工程系 集成光电子国家重点实验室， 北京100084
针对ROF（光纤无线电）通信系统中的线性动态范围的拓展问题，综述了国内外相关研究进展，梳理和阐述了影响系统动态范围的限制因素。着重介绍了基于双平行调制器结构和预失真思想的可抗色散的高线性调制技术。实验验证了原理与最佳实验条件的正确性；在25 km单模光纤传输下，相比于典型ROF系统，采用新技术的系统无失真动态范围测量值提高了至少20 dB。
光通信 光纤无线电 信号损伤补偿 线性动态范围 optical communication ROF signal damage compensation linear dynamic range
清华大学电子工程系信息技术国家实验室,集成光电子学国家重点实验室, 北京 100084
低相干光干涉法通过测量宽谱光通过待测器件之后的相位变化得到其相对延时量。采集宽谱光时域干涉数据，利用傅里叶变换提取出频域相位信息后再进行相位展开、多项式拟合处理，所得相位曲线对频率求导可得待测延时曲线。延时测量误差来源于干涉信号强度误差和纯相位误差。理论分析和仿真计算表明，延时误差与相位误差成正比；强度噪声引起的相位误差与噪声强度成正比，且该类噪声可通过曲线拟合算法得到有效抑制。实验表明，温度等环境因素引起的纯相位误差是延时测量误差的主要因素。实验上，对约19 m光子晶体光纤于1540~1560 nm波段的相对延时进行了测量，达到了0.14 ps的精度。
测量 低相干光干涉 延时误差 傅里叶变换 多项式拟合
Author Affiliations
Abstract
State Key Laboratory on Integrated Optics, Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
A novel scheme for ultra-wideband (UWB) monocycle pulse generation is proposed based on a dual-output push-pull Mach-Zehnder modulator (MZM). The MZM is driven by a non-return-to-zero (NRZ) data sequence and biased at the nonlinear point to generate edge-triggered pulses. To combine the complementary pulses forming a monocycle UWB pulse, two schemes are used to implement incoherent summation structure. A proof-of-concept experiment of UWB-over-fiber down-link system is set up. Further, by using digital signal processing (DSP) to calculate the bit error rate (BER), the transmission performance of two system configurations is studied.
超宽带脉冲 双输出口调制器 光纤传输系统 320.5540 Pulse shaping 060.5625 Radio frequency photonics 060.2330 Fiber optics communications Chinese Optics Letters
2010, 8(5): 454
清华大学电子工程系集成光电子学国家重点联合实验室, 北京 100084
报道了一种插入马赫-曾德尔(M-Z)光纤干涉仪的半导体光放大器(SOA)多波长光纤环形激光器,实现了信道间隔为100 GHz的稳定的多波长连续光激射,其输出光谱3 dB带宽为19.5 nm,消光比大于30 dB。其中在17.9 nm范围内获得了22个波长的连续光,功率不平坦度为1.2 dB,总输出功率为5.1 dBm。对该结构的多波长激光器输出光谱宽,不同波长间功率波动小的特性进行了分析,提出在较低环腔损耗下,半导体光放大器的增益饱和及四波混频(FWM)效应的共同作用使环腔内多波长光功率获得自动均衡;并对实验观测到的激光器输出光谱带宽及中心波长随半导体光放大器驱动电流降低或环腔损耗增大而减小的现象进行了讨论。
激光技术 多波长激光器 半导体光放大器 马赫-曾德尔干涉仪
