Photonic slot routing: a cost effective approach to designingall-optical access and metro networks

In the backbone network, the high level of traffic aggregation achieved by numerous users is efficiently served by means of optical circuit switched solutions-the so-called wavelength routing approach. In the access and metro networks, on the contrary, the reduced level of traffic aggregation makes wavelength routing solutions inadequate. The finer and more dynamic bandwidth allocation provided by packet-interleaved optical time-division multiplexing is thus advocated in these network areas. This article presents a survey of an OTDM approach, known as photonic slot routing, or PSR. It is illustrated how this approach may provide a cost-effective solution to deploying all-optical access and metro networks with today's technology     

Slot Routing as a Solution for Optically Transparent Scalable WDM Wide Area Networks*

All-optical Wavelength Division Multiplexing (WDM) backbones are believed to be a fundamental component in future high speed networks. Currently, the most pursued approach for Wide Area Networks (WANs) is wavelength routing, in which communication circuits are established between node pairs by means of lightpaths (paths of light) spanning one or more fiber-optic links. This approach has, however, two drawbacks. Since the number of wavelengths and links in a network is finite, not all node pairs can be connected via a dedicated lightpath directly. Consequently, some node pairs will communicate using a concatenation of lightpaths, which requires electronic switching of in transit information, loosing the advantages of optical transparency. Secondly, typically some form of (electronic) traffic grooming will be necessary to make efficient use of the fixed lightpath capacity. This paper proposes to design all-optical WANs using a novel approach, called photonic slot routing. With photonic slot routing, entire slots, each carrying multiple packets on distinct wavelengths, are switched transparently and individually, using available fast and wavelength non-sensitive devices. The advantage of using photonic slot routing is threefold. All node pairs in the network communicate all-optically. Traffic aggregation necessary to efficiently use the capacity of the wavelength channels is optically achieved. The solution is practical as it is based on proven optical technologies. In addition, through the use of wavelength non-sensitive devices the proposed WAN design yields intrinsic scalability in the number of wavelengths.     

An architecture for IP over WDM using time-division switching

This paper proposes an architecture for routing Internet protocol (IP) packets directly on optical networks. The use of label switching is assumed in the IP routers, while a new routing architecture is introduced to transport IP packets across an optical backbone network. The architecture is based on a two-tier multiplexing approach with wavelength division multiplexing (WDM) addressing the number of regional exchanges and time-division switching communicating among the hubs. Such an architecture not only has the advantages of simple network management and high efficiency with low latency; it also is scalable by addition of regional exchanges, hubs, and fibers     

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.     

A generalized framework for analyzing time-space switched opticalnetworks

The advances in photonic switching have paved the way for realizing all-optical time switched networks. The current technology of wavelength division multiplexing (WDM) offers bandwidth granularity that matches peak electronic transmission speed by dividing the fiber bandwidth into multiple wavelengths. However, the bandwidth of a single wavelength is too large for certain traffic. Time division multiplexing (TDM) allows multiple traffic streams to share the bandwidth of a wavelength efficiently. While introducing wavelength converters and time slot interchangers to improve network blocking performance, it is often of interest to know the incremental benefits offered by every additional stage of switching. As all-optical networks in the future are expected to employ heterogeneous switching architectures, it is necessary to have a generalized network model that allows the study of such networks under a unified framework. A network model, called the trunk switched network (TSN), is proposed to facilitate the modeling and analysis of such networks. An analytical model for evaluating the blocking performance of a class of TSNs is also developed. With the proposed framework, it is shown that a significant performance improvement can be obtained with a time-space switch with no wavelength conversion in multiwavelength TDM switched networks. The framework is also extended to analyze the blocking performance of multicast tree establishment in optical networks. To the best of our knowledge, this is the first work that provides an analytical model for evaluating the blocking performance for tree establishment in an optical network. The analytical model allows a comparison between the performance of various multicast tree construction algorithms and the effects of different switch architectures     

Approaches to optical Internet packet switching

Wavelength-division multiplexing is currently being deployed in telecommunications networks in order to satisfy the increased demand for capacity brought about by the explosion in Internet use. The most widely accepted network evolution prediction is via an extension of these initial predominantly point-to-point deployments, with limited system functionalities, into highly interconnected networks supporting circuit-switched paths. While current applications of WDM focus on relatively static usage of individual wavelength channels, optical switching technologies enable fast dynamic allocation of WDM channels. The challenge involves combining the advantages of these relatively coarse-grained WDM techniques with emerging optical switching capabilities to yield a high-throughput optical platform directly underpinning next-generation networks. One alternative longer-term strategy for network evolution employs optical packet switching, providing greater flexibility, functionality, and granularity. This article reviews progress on the definition of optical packet switching and routing networks capable of providing end-to-end optical paths and/or connectionless transport. To date the approaches proposed predominantly use fixed-duration optical packets with lower-bit-rate headers to facilitate processing at the network-node interfaces. Thus, the major advances toward the goal of developing an extensive optical packet-switched layer employing fixed-length packets are summarized, but initial concepts on the support of variable-length IP-like optical packets are also introduced. Particular strategies implementing the crucial optical buffering function at the switching nodes are described, motivated by the network functionalities required within the optical packet layer     

Design and cost performance of the multistage WDM-PON accessnetworks

The advantages of employing passive optical architectures in the access network have been largely recognized. Particularly, recent developments in optical technologies have made the realization of wavelength division multiplexing passive optical networks (WDM PONs) feasible and cost-effective. These networks are more future-proof than conventional PONs, thanks to their intrinsic optical transparency and their extremely high transmission capacity. A very useful optical routing device, called waveguide grating router, is the basic building-block of new PON architectures capable of connecting a large number of users or to improve the use of the optical bandwidth. In this paper, we analyze the connectivity of WDM PONs composed of multiple stages of WGR devices. A design tool is also presented which is able to easily evaluate the connectivity functions of complex WDM PONs. The feasibility of these architectures is discussed by considering the costs and the technological limitations on the optical components     

Wavelength reuse for efficient packet-switched transport in an AWG-based metro WDM network

Metro wavelength-division multiplexed (WDM) networks play an important role in the emerging Internet hierarchy; they interconnect the backbone WDM networks and the local-access networks. The current circuit-switched SONET/synchronous digital hierarchy (SDH)-over-WDM-ring metro networks are expected to become a serious bottleneck-the so-called metro gap-as they are faced with an increasing amount of bursty packet data traffic and quickly increasing bandwidths in the backbone networks and access networks. Innovative metro WDM networks that are highly efficient and able to handle variable-size packets are needed to alleviate the metro gap. In this paper, we study an arrayed-waveguide grating (AWG)-based single-hop WDM metro network. We analyze the photonic switching of variable-size packets with spatial wavelength reuse. We derive computationally efficient and accurate expressions for the network throughput and delay. Our extensive numerical investigations-based on our analytical results and simulations-reveal that spatial wavelength reuse is crucial for efficient photonic packet switching. In typical scenarios, spatial wavelength reuse increases the throughput by 60% while reducing the delay by 40%. Also, the throughput of our AWG-based network with spatial wavelength reuse is roughly 70% larger than the throughput of a comparable single-hop WDM network based on a passive star coupler (PSC).     

Nonblocking WDM switching networks with full and limited wavelength conversion

In previous years, with the rapid exhaustion of the capacity in wide area networks led by Internet and multimedia applications, demand for high bandwidth has been growing at a very fast pace. Wavelength-division multiplexing (WDM) is a promising technique for utilizing the huge available bandwidth in optical fibers. We consider efficient designs of nonblocking WDM permutation switching networks. Such designs require nontrivial extensions from the existing designs of electronic switching networks. We first propose several permutation models in WDM switching networks ranging from no wavelength conversion, to limited wavelength conversion, to full wavelength conversion, and analyze the network performance in terms of the permutation capacity and network cost, such as the number of optical cross-connect elements and the number of wavelength converters required for each model. We then give two methods for constructing nonblocking multistage WDM switching networks to reduce the network cost.     

The scalable lightwave network

In principle, an optical network employing wavelength routing, wavelength reuse, and multihop packet switching is modularly scalable to very large configurations in both the hardware and software sense. As such, it is a viable architecture for a new ATM-based telecommunications infrastructure The network architecture considered for a new, scalable, broadband telecommunications infrastructure is based on (1) the use of wavelength division multiplexing (WDM) and wavelength routing; (2) the translation of signals from one wavelength to another at the access stations; and (3) the use of multihop ATM packet switching. These principles permit networks to be built whose size is essentially unlimited     

Large-scale WDM star-based photonic ATM switches

This paper describes the large-scale photonic asynchronous transfer mode (ATM) switching systems being developed in NTT Laboratories. It uses wavelength division multiplexing (WDM) techniques to attack 1 TB/s throughput. The architecture is a simple star with modular structure and effectively combines optical WDM techniques and electrical control circuits. Recent achievements in important key technologies leading to the realization of large-scale photonic ATM switches based on the architecture are described. We show that we can obtain a 320 Gb/s system that can tolerate the polarization and wavelength dependencies of optical devices. Our experiments using rack-mounted prototypes demonstrate the feasibility of our architecture. The experiments showed stable system operation and high-speed WDM switching capability up to the total optical bandwidth of 12.8 nm, as well as successful 10 Gb/s 4×4 broadcast-and-select and 2.5 Gb/s 16×16 wavelength-routing switch operations     

自适应TDM/WDM光网络结构

WDM(波分复用)技术极大地利用了光纤的巨大带宽潜力，为此介绍了一种运用WDM技术的光网络结构，其中心局之间通过光交换设备的控制进行自适应的时分交换，同一中心局内的光交换机之间通过预约的时分复用共享所有可用波长，IP(因特网协议)数据包可以直接在该网络中透明传输。该网络结构具有组网灵活，带宽利用率高，扩容性好以及路由方法简单的优点。     

Architectures and technologies for high-speed optical data networks

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters     

A next-generation optical regional access network

We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks     

Toward wide-scale all-optical transparent networking: the ACTSoptical pan-European network (OPEN) project

The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N×10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4×4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s     

Multicast connection capacity of WDM switching networks with limited wavelength conversion

Currently, many bandwidth-intensive applications require multicast services for efficiency purposes. In particular, as wavelength division multiplexing (WDM) technique emerges as a promising solution to meet the rapidly growing demands on bandwidth in present communication networks, supporting multicast at the WDM layer becomes an important yet challenging issue. In this paper, we introduce a systematic approach to analyzing the multicast connection capacity of WDM switching networks with limited wavelength conversion. We focus on the practical all-optical limited wavelength conversion with a small conversion degree d (e.g., d=2 or 3), where an incoming wavelength can be switched to one of the d outgoing wavelengths. We then compare the multicast performance of the network with limited wavelength conversion to that of no wavelength conversion and full wavelength conversion. Our results demonstrate that limited wavelength conversion with small conversion degrees provides a considerable fraction of the performance improvement obtained by full wavelength conversion over no wavelength conversion. We also present an economical multistage switching architecture for limited wavelength conversion. Our results indicate that the multistage switching architecture along with limited wavelength conversion of small degrees is a cost-effective design for WDM multicast switching networks.     

支持灵活谱利用的超大容量全光网体系结构研究

随着超高速光传输技术的发展,支撑100Gbit/s以及更高速率的组网应用成为全光网研究的关键。文章提出支持灵活谱利用的超大容量全光网体系结构。该结构根据端口实际需要编程配置光通道带宽并实现全光交换,突破波分复用（WDM）对通道带宽的限制,解决超高速率光信号的传送问题。同时,支持面向精细颗粒带宽的全光谱域分割和疏导控制与管理,实现光层资源虚拟化与按需配置,提高光纤带宽利用率。     

用MPLS技术实现IP over WDM

提出了一种全新的高速宽带组网技术－基于MPLS的IPoverWDM网络技术,并对其进行了深入研究。这个方案在光联网技术中综合了目前先进的MPLS流量工程控制技术,特别适合于由可重构的OADM和OXC组成的以数据业务为核心的互联网络系统,而且它为最终在IP路由器上直接提供WDM复用功能铺平了道路。     

Breakthrough technologies for the high-performance electrical ATMswitching system

A high-performance electrical asynchronous transfer mode (ATM) switching system is described with the goal of Tb/s ATM switching. The first step system was to use advanced Si-bipolar very large scale integrated (VLSI) technologies and the multichip technique. 1.0 μm bipolar SST technologies and Cu-polyimide multilayer MCM realized a 160 Gb/s throughput ATM system. The performance limitations of the 160 Gb/s system were power supply/cooling and module interconnection. The new ATM switching system, named OPTIMA-1, adopted optical interconnection/distribution to overcome the limitations and achieve 640 Gb/s. The system uses high-performance complementary metal-oxide-semiconductor (CMOS) devices and optical wavelength division multiplexing (WDM) interconnection. Combining OPTIMA-1 with optical cell-by-cell routing functions, i.e., photonic packet routing, can realize variable bandwidth links for 5 Tb/s ATM systems. This paper first reviews high-performance electrical ATM (packet) switching system architecture and hardware technologies. In addition, system limitations are described. Next, the important breakthrough technology of optical WDM interconnection is highlighted. These technologies are adopted to form OPTIMA-1, a prototype of which is demonstrated. The key technologies of the system are advanced 80 Gb/s CMOS/MCM, electrical technologies, and 10 Gb/s, 8 WDM, 8×8 optical interconnection. Details of implementation technologies are also described. Optical cell-by-cell (packet-by-packet) routing is now being studied. From the architectural viewpoint, dynamic link bandwidth sharing will be adopted. In addition, an AWG that performs cell-by-cell routing and a distributed large scale ATM system are realized. Optical routing achieves the 5 Tb/s needed in future B-ISDN ATM backbone systems     

Optical Packet and Burst Switching Technologies for the Future Photonic Internet

This paper reviews advanced optical burst switching (OBS) and optical packet switching (OPS) technologies and discusses their roles in the future photonic Internet. Discussions include optoelectronic and optical systems technologies as well as systems integration into viable network elements (OBS and OPS routers). Optical label switching (OLS) offers a unified multiple-service platform with effective and agile utilization of the available optical bandwidth in support of voice, data, and multimedia services on the Internet Protocol. In particular, OLS routers with wavelength routing switching fabrics and parallel optical labeling allow forwarding of asynchronously arriving variable-length packets, bursts, and circuits. By exploiting contention resolution in wavelength, time, and space domains, the OLS routers can achieve high throughput without resorting to a store-and-forward method associated with large buffer requirements. Testbed demonstrations employing OLS edge routers show high-performance networking in support of multimedia and data communications applications over the photonic Internet with optical packets and bursts switched directly at the optical layer