Real-Time 4-Mode MDM Transmission Using Commercial 400G OTN Transceivers and All-Fiber Mode Multiplexers

Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.

Impact of individual behavior adoption heterogeneity on epidemic transmission in multiplex networks

In recent years, the impact of information diffusion and individual behavior adoption patterns on epidemic transmission in complex networks has received significant attention. In the immunization behavior adoption process, different individuals often make behavioral decisions in different ways, and it is of good practical importance to study the influence of individual heterogeneity on the behavior adoption process. In this paper, we propose a three-layer coupled model to analyze the process of co-evolution of official information diffusion, immunization behavior adoption and epidemic transmission in multiplex networks, focusing on individual heterogeneity in behavior adoption patterns. Specifically, we investigate the impact of the credibility of social media and the risk sensitivity of the population on behavior adoption in further study of the effect of heterogeneity of behavior adoption on epidemic transmission. Then we use the microscopic Markov chain approach to describe the dynamic process and capture the evolution of the epidemic threshold. Finally, we conduct extensive simulations to prove our findings. Our results suggest that enhancing the credibility of social media can raise the epidemic transmission threshold, making it effective at controlling epidemic transmission during the dynamic process. In addition, improving an individuals' risk sensitivity, and thus their taking effective protective measures, can also reduce the number of infected individuals and delay the epidemic outbreak. Our study explores the role of individual heterogeneity in behavior adoption in real networks, more clearly models the effect of the credibility of social media and risk sensitivity of the population on the epidemic transmission dynamic, and provides a useful reference for managers to formulate epidemic control and prevention policies.

Multichannel Adaptive Polarization Mode Dispersion Compensation with One Compensator in Dense Wavelength Division Multiplexing Transmission Systems

A simple two-section polarization mode dispersion(PMD) compensator is proposed for multichannel PMD compensation, which can compensate two or even more channels simultaneously. Because of the statistical characteristics and the frequency-dependence of PMD, for current single mode fiber with moderate PMD, the probability that all channels are severely degraded at the same time is extremely small, which makes it possible to compensate a dense wavelength division multiplexing(DWDM) transmission system with moderate PMD using this compensator. It is shown that the outage probability of a 40×43 Gb/s DWDM transmission system using this compensator is decreased significantly from 3.6×10-3 to 3.6×10-5.

Design of Simulation for Time-Division Multiplexing Digital Optimal Frequency Band Transmission System

This paper designs a simulation experiment model of the overall structure of time-division multiplexing digital optimal frequency band transmission system based on MATLAB simulation platform. The parameters of each module in the simulation model are set. The working process and performance of the time-division multiplexing digital optimal band transmission system are simulated. The simulation results show that the digital optimal band transmission system achieves the best transmission receiving conditions and performance, and the designed time-division multiplexing optimal digital band transmission simulation system achieves its functions. The research in this paper will help to improve the level of digital communication technology and to understand the structure of time-division multiplexing digital optimal band transmission system.

4.096 Tbit/s multidimensional multiplexing signals transmission over 1000 km few mode fiber

We experimentally transmit eight wavelength-division-multiplexing(WDM)channels,16 quadratic-amplitude-modulation(QAM)signals at 32-GBaud,over 1000 km few mode fiber(FMF).In this experiment,we use WDM,mode division multiplexing,and polarization multiplexing for signal transmission.Through the multiple-input-multiple-output(MIMO)equalization algorithms,we achieve the total line transmission rate of 4.096 Tbit/s.The results prove that the bit error rates(BERs)for the16QAM signals after 1000 km FMF transmission are below the soft-decision forward-error-correction(SD-FEC)threshold of2.4×10^(-2),and the net rate reaches 3.413 Tbit/s.Our proposed system provides a reference for the future development of high-capacity communication.

Determination of Transmission Routing of OXC Nodes Based on AWG Multiplexer by Matrix Transformation

The structures of the space switching and the wavelength switching optical cross connect (OXC) nodes which are based on the arrayed waveguide grating (AWG) multiplexer are analyzed.By the matrix transformation relation between the input and output wavelengths of the AWG multiplexer, the wavelength transmission routings of the space switching and wavelength switching OXC nodes are determined.

Information transmission through parallel multi-task-based recognition of high-resolution multiplexed orbital angular momentum

Orbital angular momentums(OAMs)greatly enhance the channel capacity in free-space optical communication.However,demodulation of superposed OAM to recognize them separately is always difficult,especially upon multiplexing more OAMs.In this work,we report a directly recognition of multiplexed fractional OAM modes,without separating them,at a resolution of 0.1 with high accuracy,using a multi-task deep learning(MTDL)model,which has not been reported before.Namely,two-mode,four-mode,and eight-mode superposed OAM beams,experimentally generated with a hologram carrying both phase and amplitude information,are well recognized by the suitable MTDL model.Two applications in information transmission are presented:the first is for 256-ary OAM shift keying via multiplexed fractional OAMs;the second is for OAM division multiplexed information transmission in an eightfold speed.The encouraging results will expand the capacity in future free-space optical communication.

OFDM Wireless Downhole Transmission Systems and Proposed SLM Method for PAPR Reduction

At present, mud pulse transmission systems are widely used in downhole data transmission. But the systems are very low in transmission efficiency, only 5-10 bits/s, with very large anti-inter-symbol-interference (ISI). It cannot meet high requirements for high-speed transmission of modern logging system. The development of communication technology has laid some foundation for this requirement. For this purpose, the Orthogonal Frequency Division Multiplexing (OFDM) Wireless Downhole Transmission Systems are proposed for the first time because of their high transmission rate, anti-inter-symbol-interference (ISI), and high spectral efficiency, etc. Due to non-linear power amplifier (PA) of logging systems with limited dynamic range, the drawbacks of high peak-average power ratio (PAPR) may outweigh all the potential benefits of OFDM wireless downhole transmission systems. Selective mapping (SLM) method can reduce the PAPR of OFDM logging signals without distortion. But at the receiver, the conventional SLM method needs exact bits of side information (SI) to recover the data signal. The probability of erroneous SI detection has a significant influence on the error performance of the system. And individual transmissions of SI result in the reduction of bandwidth efficiency. To restore the exact data signal, our scheme codes the SI bits by linear block codes (LBC), and is easily decoded by syndrome decoding. And then the coding SI bits are superimposed onto the logging signals to omit SI bits transmission. The theory and simulation results show that the proposed method has better performance than the conventional one. Accordingly, the OFDM wireless downhole transmission systems can tackle the high PAPR problem, and highten the transmission rate of logging signals.

On-chip metamaterial-enabled high-order mode-division multiplexing

Mode-division multiplexing(MDM)technology enables high-bandwidth data transmission using orthogonal waveguide modes to construct parallel data streams.However,few demonstrations have been realized for generating and supporting high-order modes,mainly due to the intrinsic large material groupvelocity dispersion(GVD),which make it challenging to selectively couple different-order spatial modes.We show the feasibility of on-chip GVD engineering by introducing a gradient-index metamaterial structure,which enables a robust and fully scalable MDM process.We demonstrate a record-high-order MDM device that supports TE_(0)–TE_(15)modes simultaneously.40-GBaud 16-ary quadrature amplitude modulation signals encoded on 16 mode channels contribute to a 2.162 Tbit∕s net data rate,which is the highest data rate ever reported for an on-chip single-wavelength transmission.Our method can effectively expand the number of channels provided by MDM technology and promote the emerging research fields with great demand for parallelism,such as high-capacity optical interconnects,high-dimensional quantum communications,and large-scale neural networks.

A Flexible ADM-based Optical Relay Transmission System

A flexible ADM-based optical relay transmission system has been developed, which provides one 34Mbps channel, two 8Mbps channels, one monitory channel and one order-wire channel. It is especially suitable for the rural communication networks and the communications in railways, oil pepelines, etc.

Finding the superior mode basis for mode-division multiplexing:a comparison of spatial modes in air-core fiber

Diverse spatial mode bases can be exploited in mode-division multiplexing(MDM)to sustain the capacity growth in fiber-optic communications,such as linearly polarized(LP)modes,vector modes,LP orbital angular momentum(LP-OAM)modes,and circularly polarized OAM(CP-OAM)modes.Nevertheless,which kind of mode bases is more appropriate to be utilized in fiber still remains unclear.Here,we aim to find the superior mode basis in MDM fiber-optic communications via a system-level comparison in air-core fiber(ACF).We first investigate the walk-off effect of four spatial mode bases over 1-km ACF,where LP and LP-OAM modes show intrinsic mode walk-off,while it is negligible for vector and CP-OAM modes.We then study the mode coupling effect of degenerate vector and CP-OAM modes over 1-km ACF under fiber perturbations,where degenerate even and odd vector modes suffer severe mode cross talk,while negligible for highorder degenerate CP-OAM modes based on the laws of angular momentum conservation.Moreover,we comprehensively evaluate the system-level performance for data-carrying single-channel and two-channel MDM transmission with different spatial mode bases under various kinds of fiber perturbations(bending,twisting,pressing,winding,and out-of-plane moving).The obtained results indicate that the CP-OAM mode basis shows superiority compared to other mode bases in MDM fiber-optic communications without using multiple-input multiple-output digital signal processing.Our findings may pave the way for robust shortreach MDM optical interconnects for data centers and high-performance computing.

Greater than 200 Gb/s Transmission Using Direct-Detection Optical OFDM Superchannel

In this paper, we propose directdetection optical orthogonal frequency division multiplexing superchannel （DDOOFDMS） and optical multiband receiving method （OMBR） to support a greater than 200 Gb/s data rate and longer distance for direct-detection systems. For the new OMBR, we discuss the optimum carriertosideband power ratio （CSPR） in the cases of backtoback and post transmission. We derive the analytical form for CSPR and theoretically verify it. A low overhead training method for estimating I/Q imbalance is also introduced in order to improve performance and maintain high system throughput. The experiment results show that these proposals enable an unprecedented data rate of 214 Gb/s （190 Gb/s without overhead） per wavelength over an unprecedented distance of 720 km SSMF in greater than 100 Gb/s DDOFDM systems.

50 GHz Spaced 4 ×40 Gbit/s WDM Transmission over 700 km Using 6 ps Bandlimited RZ Signals

In this paper, we present 50 GHz spaced 4 ×40 Gbit/s WDM transmission over 700 km using SMF-based Effective Area Enlarged Positive Dispersion Fiber in a recirculating loop. The paper uses bandlimited RZ signals and shows that transmission distance of 700 km can be achieved with BER ≤ 10-9 using 6 ps pulsewidth for each data signal. To attain this, optical filters with sharp transmission characteristics are used in both transmitter and receiver. The results demonstrated in this paper are based on simulation, and the author believes the propagation distance reached in the paper is the longest distance achieved for such system.

基于时频域联合数据辅助MIMO均衡算法的多维度复用千公里级相干传输系统

基于少模光纤的模式复用系统利用单根纤芯中的正交模式实现各独立信道的并行传输,能够有效提升系统容量,解决单模光纤系统的容量危机.本文联合使用模式复用、波分复用与偏振复用技术,基于六模渐变型光纤实现了80个波长通道下32 Gbaud四模双偏振16阶正交振幅调制信号的1000 km相干传输,并在接收端使用时频域联合数据辅助8×8多输入多输出最小均方算法,以补偿由光纤传输导致的模式耦合及模间色散等线性损伤.与传统的纯时域或纯频域多输入输出最小均方均衡算法相比,该算法分别实现了57.1%的收敛速度提升与25.1%的收敛误差下降.经过1000 km少模光纤传输后,80通道每个模式及偏振态的误码率均低于开销为20%的软判决前向纠错编码阈值2.4×10^(-2),系统净速率达68.2 Tbit/s.

基于FSC和TCSC混合复用的交直流混联线路潜供电弧特性

为提高系统运行稳定性,高补偿度串补装置广泛投入使用,但线路故障后潜供电流存在高幅值的低频分量,潜供电弧难以自熄。针对此问题,基于交直流混联输电线路,研究了不同布置方式下串补度对潜供电流与恢复电压幅值影响,提出了一种固定串补(fixed series compensation,FSC)和可控串补(thyristor controlled series compensation,TCSC)混合复用抑制潜供电弧的方法。此外,为满足线路对高补偿度的需求,设计FSC和TCSC混合复用串补度最佳配置方案。结果表明,交直流混联线路采用串补度40%的双平台分散布置方式,潜供电流与恢复电压幅值达到最小,燃弧时间最短。高补偿度串补线路TCSC采用串补度10%、20%的配置方案更利于熄弧,提高重合闸成功率。

联合物理层与MAC层的multi-TRP上行重叠传输处理机制

针对非理想回程下现有协议难以有效处理多传输接收节点(multi-TRP)场景中多定时提前(multi-TA)导致的严重上行链路(UL)重叠传输问题,联合改进物理层复用技术和介质访问控制(MAC)令牌桶技术,提出了一种新型的UL重叠传输处理机制。该新型机制通过改进物理层重叠信道识别流程、复用要求及复用规则,将物理层复用信息与重叠信息反馈至MAC层,并对MAC层令牌桶技术进行优化。通过仿真实验对所提机制与现有协议机制进行对比,结果表明,在逻辑时隙不可重叠和可重叠2种情形下,物理上行控制信道(PUCCH)实际复用数量性能平均提升了57.58%和49.40%,物理上行共享信道(PUSCH)实际可用资源数量性能平均提升了12.09%和26.03%;优先级最高逻辑信道实际占用资源数量性能平均提升了33.33%和45.48%。

基于联合功率量/载波调制的DC-DC变换器功率/数据复合传输方法

DC-DC变换器可以同时进行功率变换和数据传输。针对较低通信速率限制功率/数据复合传输(power/data multiplexing transmission,PDMT)应用的难题,提出一种联合功率量/载波调制(joint power/carrier modulation,JPCM)的新方案。与传统二进制PDMT方案不同,JPCM同时对功率量/载波进行2FSK调制,实现两种数据并行传输,可以看作一种四进制FSK,有效提高通信速率。相较于传统四进制PDMT方案,JPCM方案解调环节所需带通滤波器数目可减少一半,且软件开销更低。首先,证明PDMT在理论上的可行性;然后,根据4种不同电压纹波频率配置不同码元,并设计了包含高低数据位调制的JPCM和基于滑动傅里叶变换的数据解调方案;此外,重点分析输出参考电压突变对通信的影响,动态调整阈值可有效抑制误码;最后,搭建一个由2个Buck变换器并联的实验装置,实验结果表明在稳态、负载突变和输出参考电压突变的工况下,JPCM方案均能实现20 kb/s的通信速率,验证了该方案的有效性。

医联网下医源性风险偏差感知扩散模型及干预

首先,本研究从多重网络理论视角出发,构建医联网环境下医源性风险偏差感知多渠道扩散模型.该模型考虑了医联网环境下不同信息渠道之间医源性风险偏差感知扩散的交互影响;其次,得出区分医联网下医源性风险偏差感知在公众中扩散开来与否的阈值;最后,利用实际数据对所建立的理论模型进行参数估计及案例分析.研究结论表明:1)与仅进行正确认知的宣传推广相比,在正确认知宣传的同时进行认知纠偏,医联网下医源性风险偏差感知的扩散效率将降低的更加明显;2)与仅对一种或两种渠道中医源性风险偏差感知的扩散进行深度管控相比,如果同时对所有渠道中医源性风险偏差感知的扩散均进行适度干预,医源性风险偏差感知的扩散效率将更显著地降低.

基于QFSK调制的DC-DC变换器功率/数据复合传输方法

传统电力线通信方案的硬件设计较为复杂。DC-DC变换器具有发送数据的潜能,可进行功率/数据复合传输。文中提出一种基于四进制频移键控(QFSK)调制的电力电子开关调制方案,通过调制开关频率将数据信息嵌入原始脉宽调制(PWM)信号中,使得电压纹波携带数据的频率特征;再通过基于滑动离散傅里叶变换的解调方案实现数据接收,最终实现功率/数据的同步传输。首先,证明了PWM信号与电压纹波频率一致的关系;然后,给出数据调制与解调的方案;以负载突变工况为例,通过对Buck变换器建模,分析功率变换暂态过程对通信的干扰影响;最后,搭建由两个Buck变换器组成的实验平台,验证了所提方案可实现20 kbit/s的通信速率;并以光伏优化器为应用背景,验证了所提方案的有效性。

基于软件无线电的音视频通信一体化方案

为解决传统无线电平台对音视频传输误码率高、速率慢及设计复杂等问题,设计并提出基于ZYNQ和AD9361软件无线电方案。方案以IEEE802.11a协议为标准使用OFDM作为其主要调制技术,并通过网口实现ZYNQ与电脑主机之间的视频数据交互。功能测试结果表明,通过该方案设计的系统在天线接收范围内能持续保持数据误码率为零,并可根据实际需求灵活调整参数。此外,设计的一体化终端具有高实用性、强可扩展性和低复杂性,可广泛应用于各种环境。方案为音视频通信一体化提供全新的解决思路和方法,对无线视频通信产品开发具有较好的价值和现实意义。