Author Affiliations
Abstract
CREOL, The College of Optics & Photonics, University of Central Florida, Orlando, FL 32816, USA
Space-division multiplexing (SDM) has attracted significant attention in recent years because larger transmission capacity is enabled by more degrees of freedom (DOFs) in few-mode fibers (FMFs) compared with single-mode fibers (SMFs). To transmit independent information on spatial modes without or with minor digital signal processing (DSP), weakly-coupled FMFs are preferred in various applications. Several cases with different use of spatial DOFs in weakly-coupled FMFs are demonstrated in this work, including single-mode or mode-group-multiplexed transmission, and spatial DOFs combined with time or frequency DOF to improve the system performance.
multiplexing nonlinear optics fibers radio frequency photonics fiber optics links and subsystems few-mode fibers Chinese Optics Letters
2020, 18(4): 040601
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
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
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
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 cost-effective method of multi-receiver optical orthogonal frequency-division multiplexing (OOFDM) system is proposed to reduce the requirement for the speed of the receiver and the size of fast Fourier transform (FFT). The sampling rate of analog-to-digital converters (ADCs) can be reduced to 1/N of the original signal bandwidth in an N-receiver system. Aided by signal predistortion at the transmitter, aliasing-free signal can be retrieved independently and directly at the low speed receivers. A back-to-back experimental result is given for a two-receiver system. The effect of the electrical filters added before the ADC is studied and the analysis for filters optimization is given.
光正交频分复用 多接收 预畸变 060.0060 Fiber optics and optical communications 060.4080 Modulation 060.4230 Multiplexing Chinese Optics Letters
2010, 8(4): 377
清华大学 电子工程系集成光电子国家重点实验室,清华信息科学与技术国家实验室,北京 100084
利用光纤无源器件制作了光学90°混频器,实现了混频器90°相移的精确控制与监测,稳定时间达到12 h以上,利用此混频器研究并实现了数字相干光检测。对差分相移键控(DPSK)信号光和本振光进行混频,高速模数转换器(ADC)对混频后的基带信号采样,利用离线数字信号处理算法进行光载波相位估计和色散补偿,利用有限冲击响应(FIR)数字滤波器补偿了经过90 km光纤传输的8 Gb/s速率DPSK信号的色散失真,测量无误码。
光纤通信 零差检测 90°混频 差分相移键控 色散补偿
1 清华大学电子工程系集成光电子国家重点实验室, 北京 100084
2 清华信息科学与技术国家实验室, 北京 100084
提出并实现了用相干自混频方法监测马赫-曾德尔调制器(MZM)零偏置点漂移, 将同一光源所产生的部分未调制光和调制后的光进行混频, 利用混频光功率的最大最小值之比作为监测量监测。相比于监测信号光平均光功率的方法, 可使±5%偏置点漂移下的灵敏度从0.02 dB提高到0.3 dB。利用设计完成的硬件反馈控制系统进行了多次实验, 讨论了影响系统工作的各种因素及相应的解决办法, 结果表明该方法工作有效。
光通信 相干混频 信号监测 马赫-曾德尔调制器 偏置点控制
北京邮电大学光通信教育部重点实验室,北京,100876
作为自动交换光网络(ASON)中的核心器件,全光波长转换器在网络中发挥着重要作用.本文简述了波长变换器在全光通信网中的作用和研究意义,讲解了各种波长变换器的原理、结构和所用器件,并分析了它们各自的优缺点.
全光波长变换器 自动交换光网络 交叉增益调制 交叉相位调制 四波混频 AOWC ASON XGM XPM FWM
