Characterization of a full encoder/decoder in the AWG configuration for code-based photonic Routers-part II: experiments and applications

A 200-gigachip/s multiple encoder/decoder in an arrayed waveguide configuration, which generates and recognizes simultaneously 16 optical labels in parallel, has been fabricated. The device has been experimentally characterized, and a 10-Gb/s 50-km optical packet switching (OPS) experiment has been successfully performed: Optical packets are switched to their own destinations using a single device with a processing rate of 13 gigapackets/s.     

基于等效相移超结构光纤光栅编解码器的2.5 Gbit/s 60 km光码分多址传输实验

稳定的窄脉冲光源、高性能编解码器和具有旁瓣/噪声抑制功能的接收机是光码分多址(OCDMA)系统设计实现的3个关键模块。实验中利用增益开关脉冲光源,63位等效相移超结构布拉格光栅(EPS-SSFBG)相位编解码器和接收机门限调整技术实现了2.5 Gbit/s 60 km传输并得到了相应的误码曲线,系统在误码率(BER)等于10-9时的灵敏度为-22.5 dBm。实验结果表明,等效相移超结构布拉格光栅编解码器兼具高性能和可实现性,可用于实用化的光码分多址系统,而综合利用光域和电域的手段抑制旁瓣和噪声的影响是提高系统性能的重要手段。     

Analytical MMAP-Based Bounds for Packet Loss in Optical Packet Switching with Recirculating FDL Buffers

The major goal of optical packet switching (OPS) is to match switching technology to the huge capacities provided by (D)WDM. A crucial issue in packet switched networks is the avoidance of packet losses stemming from contention. In OPS, contention can be solved using a combination of exploitation of the wavelength domain (through wavelength conversion) and buffering. To provide optical buffering, fiber delay lines (FDLs) are used. In this paper, we focus on an optical packet switch with recirculating FDL buffers and wavelength converters. We introduce the Markovian arrival process with marked transitions (MMAP), which has very desirable properties as a traffic model for OPS performance assessment. Using this model, we determine lower and upper bounds for the packet loss rate (PLR) achieved by the aforementioned switch. The calculation of the PLR bounds through matrix analytical methods is repeated for a wide range of traffic conditions, including highly non-uniform traffic, both in space (i.e., packet destinations) and time (bursty traffic). The quality of these bounds is verified through comparison with simulation results.     

不同长度分布下的光分组交换性能研究

通过分析不同分组长度分布(PLD)对光分组交换(OPS)性能的影响,以便为OPS在不同长度业务下配置不同的冲突解决方案.研究了光分组在固定长度分布、指数分布和因特网经验长度分布下分别对没有光纤延迟线(FDL)和有FDL下的OPS的性能影响.分析和仿真表明,因特网经验长度分布的业务在没有FDL缓存的条件下,获得最低的分组丢失率(PLR)性能;而固定长度分布的业务,仅在OPS配置有FDL时才可以获得最低的PLR性能.     

业务疏导技术在WDM网络及OPS网络中的应用

在波分复用(WDM)光网络中,可使用业务疏导(Traffic Grooming)技术来提高网络性能,降低网络成本.详细阐述了WDM光网络中业务疏导的基本概念及主要目标,并对国内外研究现状进行了总结.最后介绍了OPS光交换网络中使用的业务疏导技术.     

Contribution to future metropolitan access network planning considering link failures in photonic switched networks

Photonic switching for traffic optimization in Metropolitan Access Optical Networks using technologies of optical packet/burst switching (OPS/OBS) seems to be a future-proof solution considering high capacity and the highly variable traffic in these networks. Looking for this future, we propose a study based on the analyze of survivability of traffic unconsidering protection mechanism but considering mesh and ring efficient topologies with node architecture to OPS. The results are obtained through computer modeling and simulation. The main parameters analyzed are as follows: capacity, average number of hops, packet loss fraction, and link utilization for each topology. These parameters are adopted to evaluate the performance of each topology considering failures. Minimum electronic buffering is included at node ingress (client side) to avoid packet loss in the access to the optical layer: high throughput and low latency. It is also observed that optical buffering is not necessary for adequate network performance.     

Demonstration of over 128-gb/s-capacity (12-User/spl times/10.71-gb/s/user) asynchronous OCDMA using FEC and AWG-based multiport optical encoder/decoders

For the first time, an arrayed-waveguide-grating (AWG)-based multiport optical encoder/decoder (E/D) and forward-error-correction (FEC) technique are applied in an optical code-division multiple-access (OCDMA) system. The AWG-based OCDMA E/D with high power contrast ratio between auto-/cross-correlation can significantly suppress the interference noises in an asynchronous OCDMA system without using ultralong optical codes and optical thresholder. A 12-user 10.71-Gb/s asynchronous OCDMA experiment has been successfully demonstrated to transmit ITU-T G.709 OTN frames including FEC.     

Spectral efficiency of OCDMA systems with coherent pulsed sources

We present a model to evaluate the upper limit of the spectral efficiency of optical code-division multiple-access (OCDMA) systems with coherent sources. Phase-encoded and direct-sequence OCDMA systems are evaluated using this model. The results show that a spectral efficiency of 2.24/spl times/10/sup -2/ b/s/spl middot/ Hz can be achieved with a maximum bit error rate of 10/sup -10/ in these systems of the number of users. This result demonstrates that the maximum spectral efficiency of OCDMA systems with coherent sources is at least a factor of 5 higher than OCDMA systems with incoherent sources.     

Demonstration of 10 Gbit Ethernet/Optical-Packet Converter for IP Over Optical Packet Switching Network

We developed novel network interfaces, for example 10 Gbit Ethernet to 80 Gbit/s optical-packet (10 GbitE–80 GbitOP) or 80 Gbit/s optical-packet to 10 Gbit Ethernet (80 GbitOP–10 GbitE) converters (collectively called as 10 GbitE/80 GbitOP converters), to connect optical packet switching (OPS) networks with IP technology-based networks. By using newly developed arrayed burst-mode optical packet transmitters/receivers together, the 10 GbitE–80 GbitOP converter at the ingress edge node of the OPS network encapsulates an IP packet into an $80(8lambdatimes 10) {rm Gbit/s}$ dense wavelength division multiplexing (DWDM)-based optical packets and generates an optical label based on a lookup table and the destination addresses of the IP packet. The 80 GbitOP–10 GbitE converter at the egress edge node decapsulates the IP packet from the optical packet and generates a 10 GbitE frame accommodating the IP packet according to a lookup table. By using these network interface devices and OPS system based on multiple optical label processing, we achieved, for the first time, 74-km single-mode fiber transmission, switching, and buffering of $80(8lambdatimes 10) {rm Gbit/s}$ DWDM-based optical packets encapsulating almost 10 Gbit/s IP packets with error-free operation (IP packet loss rate $≪ 10^{-6}$).      

A fully implemented 12 /spl times/ 12 data vortex optical packet switching interconnection network

A fully functional optical packet switching (OPS) interconnection network based on the data vortex architecture is presented. The photonic switching fabric uniquely capitalizes on the enormous bandwidth advantage of wavelength division multiplexing (WDM) wavelength parallelism while delivering minimal packet transit latency. Utilizing semiconductor optical amplifier (SOA)-based switching nodes and conventional fiber-optic technology, the 12-port system exhibits a capacity of nearly 1 Tb/s. Optical packets containing an eight-wavelength WDM payload with 10 Gb/s per wavelength are routed successfully to all 12 ports while maintaining a bit error rate (BER) of 10/sup -12/ or better. Median port-to-port latencies of 110 ns are achieved with a distributed deflection routing network that resolves packet contention on-the-fly without the use of optical buffers and maintains the entire payload path in the optical domain.     

High-Performance Hybrid-Switching Optical Router for IP over WDM Integration

Because pure electrical routers with their bandwidth limitations can hardly keep up with the tremendous traffic growth in the Internet, optical routers based on various optical switching techniques including optical wavelength switching (OWS), optical burst switching (OBS), and optical packet switching (OPS) have been suggested to cope with this problem. However, because OBS and OPS are both in their early experimental phase and OWS only provides coarse granularity switching, a hybrid-switching optical router with combined OWS and electrical packet switching is a necessity in order to accommodate the entire multi-granularity traffic with multi-service requirements in a cost-effective manner. Its coordination capability of optical circuit switching and electrical packet switching enables efficient/intelligent usage of network resources. In this paper, we first review research and developments of such IP routers employing optical switching/interconnection techniques and examine how these techniques can be used inside routers to scale node capacity and to improve optical Internet performance. We also present and study the performance of a terabit optical router with an optical-electrical hybrid-switching fabric. The node architecture is based on the idea of IP over WDM integration with Generalized Multi-Protocol Label Switching (GMPLS). The network-level performance evaluations show that the proposed hybrid-switching optical router is a cost-effective solution for building the next generation GMPLS-based multi-granularity optical Internet.     

Packet Pacing in Small Buffer Optical Packet Switched Networks

In the absence of a cost-effective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. To mitigate the performance degradation resulting from small buffers, this paper proposes that optical edge nodes “pace” the injection of traffic into the OPS core. Our contributions relating to pacing in OPS networks are three-fold: first, we develop real-time pacing algorithms of poly-logarithmic complexity that are feasible for practical implementation in emerging high-speed OPS networks. Second, we provide an analytical quantification of the benefits of pacing in reducing traffic burstiness and traffic loss at a link with very small buffers. Third, we show via simulations of realistic network topologies that pacing can significantly reduce network losses at the expense of a small and bounded increase in end-to-end delay for real-time traffic flows. We argue that the loss-delay tradeoff mechanism provided by pacing can be instrumental in overcoming the performance hurdle arising from the scarcity of buffers in OPS networks.      

混合缓存型异步光分组交换的一种改进FF-VF算法

光纤延迟线（FDL）是异步光分组交换（OPS）采用的时域冲突解决方案,通过计算其分组丢失率（PLR）发现,在业务负载高,特别是业务负载大于0．7时,PLR性能较差。研究以FDL作为主要的常规缓存、以电存储器作为辅助缓存的光电混合缓存结构,并用改进的首选即中的填空（IFF-VF）算法调度冲突的分组,达到改善可变长OPS的PLR目的。分析和仿真结果表明,光电混合缓存和IFF-VF算法能改善可变长OPS在负载较高时的PLR性能,并减少FDL的数目。     

IP Routing and Traffic Analysis in Coherent Optical CDMA Networks

This paper proposes a novel IP routing schemes over coherent optical code-division multiple-access (OCDMA) network. As spreading code, flexible in length double-padded modified prime code (DPMPC) has been deployed. The performance has been analyzed in terms of the users' channel utilization factor in the network. The results are comparable with previous schemes and indicate that the architecture is power efficient and capable of accommodating greater number of active users with advantage of shorter code length (i.e., higher bit rate). It is shown that for a maximum bit rate the network performance can be improved by reducing the channel utilization. However, when each user in the network has a fixed bit rate, optimal channel utilization can be set for the overall network performance. Additionally, each IP packet is buffered only at the edge of this network, thus the buffer delay is significantly reduced compared with traditional routing schemes. Since the optical encoder is adjusted for number of packets rather than individually, the encoder adjusting time is also significantly reduced. Analytical results clearly indicate that coherent OCDMA technique can be a fine candidate for the future ultra fast optical IP networks.     

Node pacing for small optical RAM-buffered packet-switching networks

One of the difficulties with optical packet switched (OPS) networks is buffering optical packets in the network. The only available solution that can currently be used for buffering in the optical domain is using long fiber lines called fiber delay lines (FDLs), which have severe limitations. Moreover, the research on optical RAM presently being done is not expected to achieve a large capacity soon. However, the burstiness of Internet traffic causes high packet drop rates and low utilization in very small buffered OPS networks. We therefore propose a new node-based pacing algorithm for decreasing burstiness. We show that by applying some simple pacing at the edge or core backbone nodes, the performance of very small optical RAM buffered core OPS networks with variable-length packets can be notably increased.     

Evaluation of throughput and protection in optically switched metropolitan network architectures

In this study, we investigate the performance of optical packet/burst switched (OPS/OBS) architectures connected as mesh and as ring topologies for future optical metropolitan networks. Network throughput and protection to link failure under uniform traffic distribution for all nodes are investigated to evaluate the sensitivity of OPS/OBSN performance. Our data are based on analytic results and computer simulations that include a comparison between various mesh and ring topologies. We also consider detailed traffic distributions over the network links and the impact caused by failure of more or less loaded links, thus providing a method to select links that require protection, which can be very useful in network planning.     

Traffic models for slotted optical packet switched networks

Optical packet switching (OPS) has emerged as a promising architecture for the future all-optical network scenario. In order to have a successful deployment of OPS networks, several networking issues must be resolved, e.g., how to resolve contentions and how to provide Quality-of-Service (QoS) differentiation. Such networking studies often rely on teletraffic analysis in order to quantify the performance of the OPS network. In this paper, we introduce new and review existing traffic models for slotted buffer-less OPS networks. In particular, we present a novel asymmetric traffic model, suitable for studying the effects of non-uniform traffic. Optical packet switches with and without wavelength conversion are studied. Numerical evaluations and a comparison study of the presented traffic models are reported. The main contributions of this paper are to advance the field of establishing a theoretical framework for slotted OPS networks and to act as a tutorial for teletraffic engineering in such networks. http://www.item.ntnu.no/~haraldov.     

Field Trial of Duplex, 10 Gbps $,times,$8-User DPSK-OCDMA System Using a Single 16$,times,$ 16 Multi-Port Encoder/Decoder and 16-Level Phase-Shifted SSFBG Encoder/Decoders

An optical code-division multiple access (OCDMA) over wavelength-division multiplexing (WDM) system could be one promising solution to the symmetric Gigabit access network with high spectral efficiency, cost effective, good flexibility and enhanced security. A cost-effective OCDMA/WDM system using a single multi-port en/decoder at an optical line terminal (OLT) and superstructured fiber Bragg grating (SSFBG) encoder/decoders at each optical network unit (ONU) in an optical network has been proposed and demonstrated. In this paper, we prepare 16-chip, 16-level phase-shifted SSFBG encoder/decoders and develop the full-asynchronous 10 Gigabit Ethernet (10 GbE) interface OCDMA prototype for the first time. Field trials of duplex, fully-asynchronous, 10 Gbps$,times,$8-user DPSK-OCDMA system over 100 km using hybrid multi-port and SSFBG encoder/decoder are demonstrated.      

The Data Vortex Optical Packet Switched Interconnection Network

A complete review of the data vortex optical packet switched (OPS) interconnection network architecture is presented. The distributed multistage network topology is based on a banyan structure and incorporates a deflection routing scheme ideally suited for implementation with optical components. An implemented 12-port system prototype employs broadband semiconductor optical amplifier switching nodes and is capable of successfully routing multichannel wavelength-division multiplexing packets while maintaining practically error-free signal integrity (BER $ ≪ {hbox{ 10}}^{ - 12}$ ) with median latencies of 110 ns. Packet contentions are resolved without the use of optical buffers via a distributed deflection routing control scheme. The entire payload path in the optical domain exhibits a capacity of nearly 1 Tb/s. Further experimental measurements investigate the OPS interconnection network's flexibility and robustness in terms of optical power dynamic range and network timing. Subsequent experimental investigations support the physical layer scalability of the implemented architecture and serve to substantiate the merits of the data vortex OPS network architectural paradigm. Finally, modified design considerations that aim to increase the network throughput and device-level performance are presented.      

光码分多址多用户系统实验及性能分析

报道采用光码分多分址(OCDMA)技术实现了3用户通信的实验,传输速率为2.5 Gchip/s,传输距离为20 km.给出了OCDMA系统基本参数设计方法,搭建并实现了OCDMA实验,通过设计实验系统与得到的实验结果作了详细的分析,结果表明,我们成功实现了3用户传输2.5 Gchip/s的OCDMA通信实验,并验证了多用户干扰是OCDMA系统下降的主要噪声源.