A passive optical network based on optical code division multiplexing and time division multiple access technology

A passive optical network （PON） scheme based on optical code division multiplexing （OCDM） for the downstream traffics is proposed and analyzed in detail. In the PON, the downstream traffics are broadcasted by OCDM technology to guarantee the security, while the upstream traffics pass through the same optical fiber by the common time division multiple access （TDMA） technology to decrease the cost. This schemes are denoted as OCDM/TDMA-PON, which can be applied to an optical access network （OAN） with full services on demand, such as Internet protocol, video on demand, tele-presence and high quality audio. The proposed OCDM/TDMA-PON scheme combines advantages of PON, TDMA, and OCDM technology. Simulation results indicate that the designed scheme improves the OAN performance, and enhances flexibility and scalability of the system.

Minimizing Traffic Blocking and Inter-Crosstalk in Spatial Division Multiplexing over Elastic Optical Networking

As a promising solution, virtualization is vigorously developed to eliminate the ossification of traditional Internet infrastructure and enhance the flexibility in sharing the substrate network (SN) resources including computing, storage, bandwidth, etc. With network virtualization, cloud service providers can utilize the shared substrate resources to provision virtual networks (VNs) and facilitate a wide and diverse range of applications. As more and more internet applications migrate to the cloud, the resource efficiency and the survivability of VNs, such as single link failure or large-scale disaster survivability, have become crucial issues. Elastic optical networks have emerged in recent years as a strategy for dealing with the divergence of network application bandwidth needs. The network capacity has been constrained due to the usage of only two multiplexing dimensions. As transmission rates rise, so does the demand for network failure protection. Due to their end-to-end solutions, those safe-guarding paths are of particular importance among the protection methods. Due to their end-to-end solutions, those safeguarding paths are of particular importance among the protection methods. This paper presents approaches that provide a failure-independent route-protecting p-cycle for path protection in space-division multiplexed elastic optical networks. This letter looks at two SDM network challenges and presents a heuristic technique (k-shortest path) for each. In the first approach, we study a virtual network embedding (SVNE) problem and propose an algorithm for EONs, which can combat against single-link failures. We evaluate the proposed POPETA algorithm and compare its performance with some counterpart algorithms. Simulation results demonstrate that the proposed algorithm can achieve satisfactory performance in terms of spectrum utilization and blocking ratio, even if with a higher backup redundancy ratio.

Traffic Scheduling in WDM Passive Optical Network with Delay Guarantee

WDM passive optical network becomes more favorable as the required bandwidth increases, but currently few media access control algorithms adapted to WDM acc ess network. This paper presented a new scheduling algorithm for bandwidth shari ng in WDM passive optical networks, which provides per-flow delay guarantee and supports variable-length packets scheduling. Through theoretical analysis and simulation, the end-to-end delay bound and throughput fairness of the algori thm was demonstrated.

Cyclic polling-based dynamic wavelength and bandwidth allocation in wavelength division multiplexing passive optical networks

Cyclic polling-based dynamic wavelength and bandwidth allocation algorithm supporting differentiated classes of services in wavelength division multiplexing （WDM） passive optical networks （PONs） is proposed. In this algorithm, the optical line terminal （OLT） polls for optical network unit （ONU） requests to transmit data in a cyclic manner. Services are categorized into three classes： expedited forward （EF） priority, assured forwarding （AF） priority, and best effort （BE） priority. The OLT assigns bandwidth for different priorities with different strategies. Simulation results show that the proposed algorithm saves a lot of downstream bandwidth under low load and does not show the light-load penalty compared with the simultaneous and interleaved polling schemes.

2 Tbit/s based coherent wavelength division multiplexing passive optical network for 5G transport

Future high-speed mobile communication systems require low latency and high capacity networks.Coherent wavelength division multiplexing(WDM)passive optical network(PON)scheme is expected to play a vital role in these systems.In this paper,coherent WDM-PON scheme based on dual-polarization 16-quadrature amplitude modulation(DP-16 QAM)transceiver has been investigated.The aim of this scheme is to build a 2 Tbit/s(125 Gbit/s/λ×16 wavelengths)network that will be used in the construction of the transport architecture of fifth generation(5 G)and beyond 5 G(B5 G)cellular networks either in mobile front haul(MFH)or mobile back haul(MBH).The results indicate that the proposed scheme is very adequate for both 5 G and B5 G cellular networks requirements.

Fault monitoring in passive optical network using code division multiplex-based dual-OTDR traces comparison

A dual optical time domain reflectometry （OTDR） system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is proposed in a time-division multiplexing passive optical network （PON）. The proposed scheme accomplishes the fiber fault monitoring by comparing the different wavelength＇s testing curves. Complete complementary code is utilized to measure multiple wavelength signals simultaneously with only one receiver and to improve the dynamic range of this system. The PON system consisting of 20 km feeding fiber and a 1：16 splitter is investigated by the experiments. The experimental results show that the faulty branch can be successfully identified by using our scheme. What is more, we also demonstrate that our scheme can be applied to the multi-stage PON.

Optimization of Disjoints Using WDM-PON in an Optical Network

An optical network is a type of data communication network built with optical fibre technology. It utilizes optical fibre cables as the primary communication medium for converting data and passing data as light pulses between sender and receiver nodes. The major issue in optical networking is disjoints that occur in the network. A polynomial time algorithm Wavelength Division Multiplexing-Passive Optical Networking (WDM-PON) computes disjoints of an optical network and reduces the count of disjoints that occur in the network by separating Optical Network Units (ONU) into several virtual point-to-point connections. The Arrayed Waveguide Grating (AWG) filter is included in WDM-PON to avoid the traffic in the network thereby increasing the bandwidth capacity. In case of a failure or disjoint Ant Colony Optimization (ACO) algorithm is used to find the optimized shortest path for re-routing. For enhanced security, modified Rivert Shamir Adleman (RSA) algorithm encrypts the message during communication between the nodes. The efficiency is found to be improved in terms of delay in packet delivery, longer optical reach, optimized shortest path, packet error rate.

An Arrangement of Channels and Transceivers in Optical Packet Switching Networks

Based on a media access and control（MAC）protocol,an arrangement of channels and transceivers in optical packet switching dense wavelength division multiplexing（DWDM）networks is proposed in this paper.In order to reduce the cost of nodes,fixed transmitters and receivers are used instead of tunable transmitters and receivers.Two fixed transmitters and many fixed receivers are used in each node in the scheme.The average waiting delay of this scheme is analyzed through mathematics and computer simulation.The result shows that the property of the scheme is almost the same as using tunable transmitter and receiver.Furthermore,if the tuning time of tunable transmitters is taken into account,the performance of the tunable transmitter scheme is poor than this scheme at the average waiting delay and throughput of the network.

Crosstalk-aware RCSA for spatial division multiplexing enabled elastic optical networks with multi-core fibers

In this Letter, we propose two crosstalk-aware routing, core, and spectrum assignment （CA-RCSA） algorithms for spatial division multiplexing enabled elastic optical networks （SDM-EONs） with multi-core fibers. First, the RCSA problem is modeled, and then a metric, i.e., CA spectrum compactness （CASC）, is designed to measure the spectrum status in SDM-EONs. Based on CASC, we propose two CA-RCSA algorithms, the first-fit （FF） CASC algorithm and the random-fit （RF） CASC algorithm. Simulation results show that our proposed algorithms can achieve better performance than the baseline algorithm in terms of blocking probability and spectrum utilization, with FF-CASC providing the best performance.

Hybrid WDM/TDM PON system employing an all-optical wavelength converter

A new hybrid WDM/TDM passive optical network （PON） implemented by using all-optical wavelength converters （AOWCs） is proposed. The AOWCs are based on the cross-gain modulation （XGM） effect of the semiconductor optical amplifier （SOA）. Moreover, the feasibility of this sys- tem is experimentally demonstrated by evaluating the impacts of the optical wavelength conversion, time domain waveforms, eye diagrams and bit-error-rate （BER） in AOWC. The results show that the proposal will be a promising solution for the next generation access networks.

基于光开关阵列的灵活TWDM-PON系统研究

为了满足接入网日益增长的业务流量需求,解决当前因架构固定、资源维度有限而导致的不同无源光网络之间波长无法灵活分配的的问题,提出了一种将发射固定波长的激光器与光开关阵列组合的时分波分混合复用无源光网络结构。在这种新的系统结构中,下行波长资源被集中化处理,采用在局端配置光开关阵列的方法实现波长在不同网络之间的灵活调度,降低系统总体成本的同时能够用来解决负载平衡、流量“潮汐效应”、网络资源利用率低下等问题。通过理论分析和仿真实验验证了系统的可行性,得出该结构与传统无源光网络的兼容性、波长资源的共享性、系统低成本以及节能的特点。结果表明,在没有色散补偿的情况下,信号可以覆盖30 km的传输距离,同时服务512个用户。该研究可以为典型应用场景下的无源光网络部署提供参考。

光载波替换技术在OFDM-TDM-PON接入网的应用

OFDM-TDM-PON接入网是未来光接入网发展的重点方向,为了有效降低OFDM-TDM-PON接入网上行链路中的光拍频噪声干扰,提出了三种基于光载波替换技术的应用方案,并对各种应用方案的上行链路性能进行了分析。结果表明,三种应用方案均能有效抑制上行链路中的拍频噪声干扰,提高上行链路的接入性能。

基于信息熵特征的正交频分复用无源光网络系统

越来越多的ONU接入无源光网络,易发生网络拥塞问题,信息传输延迟,数据丢包等现象出现,为此,设计了基于信息熵特征的正交频分复用无源光网络系统。由光线路终端(OLT)、光分配网络(ODN)和光网络单元(ONU)组成系统框架结构,采用分散分光形式设计系统组网结构,借助My SQL,设计系统数据库以及数据表。设计系统三个主要功能模块,即无源光信息收发模块、基于信息熵的ONU负载判断模块以及无源光网络带宽分配模块,通过合理分配带宽资源,提高无源光网络传输能力。结果表明:无源光网络系统5次轮询后传输时隙长度均在4 ms以下,无源光网络通信传输效率高,能够快速实现信息传递,极大避免时延问题。

电力通信接入网多业务安全承载技术应用探讨

针对电力通信接入网多业务综合接入、多网络协同承载和多业务安全隔离传输的需求,结合电力通信接入网的建设现状,提出基于时分波分复用无源光网络(TWDM-PON)技术的电力多业务安全接入解决方案。分析了电力通信接入网现有通信技术存在的不足,研究了TWDM-PON技术的网络架构体系以及对多业务承载的适应性,提出了实现多业务统一承载的动态资源调度机制和基于交换与存储资源的隔离技术,并搭建实验环境,验证分析了TWDM-PON在电力通信接入网应用的关键性能指标,为电力多业务统一承载探索了一种可行的通信网络建设模式。

Recent Research Progress in λ-Tunable WDM/TDM-PON

This paper describes the current research status of theλ-tunable Wavelength-Division Multiplexing/Time-Division-Multiplexing-Passive Optical Network(WDM/TDM-PON). This optical access system realizes new cost-effective operations from the network operator′s point of view.The main feature of the proposed system is that it aggressively exploits wavelength tunability.We classify the system configurations and applications.Then,we describe key technologies,namely newly developedλ-tuning burst-mode transceivers and a widely applicable Dynamic Wavelength and Bandwith Allocation(DWBA)algorithm.Finally,we summarize our research and discuss several issues related to the λ-tunable Wavelength-Division Multiplexing/Time-Division-MultiplexingPassive Optical Network(WDM/TDM-PON).

Novel applications of space-division multiplexing

Space-division multiplexing （SDM） using multi-core fibers （MCFs） and few-mode fibers （FMFs） was proposed as a solution to increase capacity and/or reduce the cost per bit of fiber-optic transmission. Advances in passive and active SDM devices as well as digital signal processing have led to impressive SDM transmission demonstrations in the laboratory. Although the perceived advantages in terms of capacity and cost per bit that SDM offers over parallel SMF bundles are not universally accepted, SDM is beginning to emerge as an indispensable solution in major network segments. The introduction of the spatial degree of freedom allows optical networks to overcome fundamental limitations such as fiber nonlinearity as well practical limitations such as power delivery. We describe these application scenarios that the optical communications industry has already began to explore. From a fundamental science point of view, concepts such as the principal modes, generalized Stokes space, and multi-component solitons discovered in SDM research will likely have a broad impact in other areas of science and engineering.

光纤网时间同步性能计量校准装置研制

为解决光纤时间传递系统中存在的远距离传递准确度低的问题,分析了环回法、双纤双向时间同步、双向波分复用、双向时分复用四种主流的高精度光纤时间传递方法的基本原理和技术特点,在此基础上研制了单信道时频传递装置。该装置采用电学相位补偿法实现频率传递同步,采用环回法与时分复用相结合的方法实现时间传递同步;使用1秒脉冲(Pulse Per Second,PPS)和100 MHz共同标记时刻信号,其中1 PPS作为时刻粗标记,100 MHz作为时刻细标记,实现高精度时间同步。经实验证明,单信道时频传递装置的不确定度约为13 ps,能够满足现有光纤时频同步网计量校准的要求。该装置在多级时间传递同步、光纤时频同步网计量校准等领域中具有广阔的应用前景,为建设高稳定性、高可靠性和高精度的授时体系提供了重要技术支撑。

基于特征向量构建的相干正交频分复用无源光网络系统

设计基于特征向量构建的相干正交频分复用无源光网络系统,避免无源光网络受到码间串扰的影响。设置光梳状谱发生器作为系统光源,生成光波信号,利用波分复用器分离生成的光波信号,完成分离后信号传送至IQ调制器,IQ调制器利用正交频分复用信号调制与解调过程调制分离信号,通过波分复用器集合完成调制的两路光波,集合后光波利用传输光纤传送至光节点;光节点中的相干接收器接收光波信号后,利用光电二极管传送至SVM均衡器,SVM均衡器利用特征向量构建方案均衡光波信号,实现信号的高效传输。系统测试结果表明,驱动功率为11 dB、本振光功率为6 dBm时,系统具有最佳的通信性能,所设计系统可有效改善码间串扰情况,均衡通信信号。

新型混合TDM/WDM无源光网络

讨论了4种不同类型的混合型时分/波分无源光网络,并从网络架构、拓扑形态、网络灵活性和应用模式等方面进行了综合分析和比较.分析结果表明,混合型时分/波分无源光网络兼具TDM-PON无源光分支和WDM-PON波长路由的优点,在带宽容量和用户成本方面进行折中考虑,使整个网络在用户扩展和带宽升级方面具有较好的灵活性,同时又保证了较高的用户带宽和较低的用户使用成本.4种混合型网络架构都具有相当大的灵活性和自由度,可以有效应用于从TDM-PON网络到WDM-PON网络的过渡升级.