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
提出一种新型四倍频技术用于单边带光载毫米波信号的产生。该技术使用一个双平行马赫曾德尔调制器(DPMZM)实现四倍频的单边带调制，通过微波移相和双平行马赫曾德尔(MZ)调制器偏置点控制，产生出包含载波边带和两个二阶边带的光谱，用光滤波器滤除光载波后得到频率为四倍微波本振频率的光载毫米波信号。基于上述技术，搭建了光载射频(RoF)传输实验系统，该RoF系统用10 GHz微波源产生了40 GHz的光载毫米波并承载了1 Gb/s的基带数据。实验结果表明，光载毫米波信号经20 km标准单模光纤传输后，功率代价仅为0.8 dB。
光通信 上变频 光学单边带调制 光载射频
Author Affiliations
Abstract
State Key Laboratory on Integrated Optoelectronics/Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
We demonstrate a novel 40-Gb/s transmission system over a 10×101-km standard single mode fiber (SSMF) loop. This system features polarization multiplexed quadrature phase shift keying (PolMux-QPSK), lowvoltage modulation of 2-V peak-to-peak signal amplitude, and home-made 90? optical hybrid with singleended digital coherent detection. Any power amplifers before the modulator and balanced detectors are not used. In the case of low-voltage modulation, coherent detection is much less sensitive to modulator bias offset than delay interferometer-based demodulation.
偏振复用QPSK 单端检测 40Gb/s 光纤环路 060.0060 Fiber optics and optical communications 060.1660 Coherent communications 060.5060 Phase modulation Chinese Optics Letters
2010, 8(10): 976
Author Affiliations
Abstract
State Key Laboratory on Integrated Optoelectronics/Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
A method of multi-channel receiving for high bit rate heterodyne direct-detection optical orthogonal frequency-division-multiplexing (OOFDM) system is proposed to reduce the sampling rate demand of analog-to-digital converter (ADC). The sampling rate of ADCs can be reduced to 1/N that of the original signal bandwidth in an N-channel receiving system. Aided by a succeeding digital signal processing (DSP) at the receiver, aliasing free signal can be recovered. A back-to-back experimental result is given for a 4-channel system, based on which, a down conversion process for heterodyne can be reduced. The signal rebuilding algorithm is given and analyzed in its complexity and noise tolerance.
光正交频分复用 采样 多通道接收 060.0060 Fiber optics and optical communications 060.4080 Modulation 060.4230 Multiplexing Chinese Optics Letters
2010, 8(9): 819
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国家重点联合实验室,清华信息科学与技术国家实验室,北京 100084
利用光纤偏振分束器和3 dB耦合器搭建偏振分集90°光学混频器,采用单端接收实现了偏振分集的相干接收机。实现了10 Gb/s偏振复用差分相移键控(DPSK)光信号,经过280 km普通单模光纤(SSMF)和掺铒光纤放大器(EDFA)传输后的数字相干接收,测量无误码。研究了数字相干光接收中的各种信号处理算法。采用数字信号处理算法完成载波相位估计,数字滤波器补偿光纤色散,恒模算法进行自适应数字偏振解复用等。研究了90°光学混频器的非理想正交特性,运用统计方法补偿了光学混频器偏离90°的误差,此算法和信号格式以及光纤色散等因素无关。使用恒模算法实现数字偏振解复用,该算法收敛时间小于0.5 μs。
光纤通信 数字相干检测 恒模算法 差分相移控 数字偏振解复用
