All-optical network subsystems using integrated SOA-based optical gates and flip-flops for label-swapped networks

In this letter, we demonstrate that all-optical network subsystems, offering intelligence in the optical layer, can be constructed by functional integration of integrated all-optical logic gates and flip-flops. In this context, we show 10-Gb/s all-optical 2-bit label address recognition by interconnecting two optical gates that perform xor operation on incoming optical labels. We also demonstrate 40-Gb/s all-optical wavelength-switching through an optically controlled wavelength converter, consisting of an integrated flip-flop prototype device driven by an integrated optical gate. The system-level advantages of these all-optical subsystems combined with their realization with compact integrated devices, suggest that they are strong candidates for future packet/label switched optical networks.     

Cascadability study for optical label swapping using synchronous phase modulation

We experimentally investigate the cascadability of optical label swapping using a synchronous phase modulation technique without wavelength conversion in a recirculating loop to emulate multihop networks. We find that the power penalties for both label and payload are below 1 dB at 10/sup -7/ bit-error rate after five hops. We also show that a system penalty can be maintained below 1 dB for an accumulated timing mismatch of 20% of bit period using synchronous phase modulation-based optical label swapping. The results show the potential to save up to 80% of wavelength converters in optical packet switched networks applications.     

High-capacity multiservice optical label switching for the next-generation Internet

This article presents an optical label switching technology geared toward the next-generation Internet, and highlights its promising potential to accommodate packet, burst, and circuit traffic in a unified optical layer. In particular, we provide detailed discussions on an architecture design for a high capacity optical label switching router by considering enabling optical technologies. In pursuit of an effective contention resolution scheme, we investigate an end-to-end solution by incorporating a traffic shaping function at the network edge with wavelength, time, and space dimensions contention resolution in the core network. Experimental results indicate that this scheme is capable of achieving very low packet loss rates. Furthermore, due to its natural compatibility with GMPLS architecture, optical label switching has great potential for a seamless upgrade of today's optical networks toward the next generation Internet.     

All-Optical Processing Based on a Logic xor Gate and a Flip-Flop Memory for Packet-Switched Networks

The routing functionality by all-optically interconnecting semiconductor-based all-optical logic gates and flip-flops is demonstrated in the frame of an all-optical label swapping (AOLS) network. We experimentally show that the output of the all-optical 2-bit correlator is capable of toggling the states of the integrated flip-flop every 2.5 ns via an adaptation stage. High extinction ratios are obtained at the output of the flip-flop, which can be used to feed a high-speed wavelength converter to complete the routing functionality of the AOLS node. The potential integration of these semiconductor optical amplifier integrated Mach-Zehnder interferometer-based devices make the proposed approach a very interesting solution for future packet switched optical networks.     

光互联网与IP over DWDM技术的演进

探讨了光互联网的支撑技术和演进策略,分析了IP over DWDM等关键支撑技术的难点与发展趋势。首先,比较分析了若干种典型的网络层次模型及其性能,指出IP over DWDM是实现未来宽带互联网的关键支撑技术;其次,分析了IP over DWDM的技术难点,指出全光信号处理和多协议标签交换技术是实现IP over DWDM的重要手段,并预言了在相关技术成熟后,光分组网技术将进一步推动光互联网的发展。     

广义多协议标签交换GMPLS

未来的光传输网将由下列网络单元组成：路由器、交换机、DWDM系统、ADM、光交叉连接设备（OXC）等。为使由这些网络单元组成的网络具有很好的鲁棒特性,IETF的IPO工作组提出用广义的多协议标签交换（GMPLS）业动态地配置资源,充分利用保护和恢复技术提高网络的生存性,GMPLS将时隙、波长和光纤端口作为标签用于数据传发,由于各标签之间对应的数据粒度不同,GMPLS采用扩展的MPLS信令和路由来转发标签并建立相应的标签交换路径。     

MPLS Recovery Mechanisms for IP-over-WDM Networks

Due to the fast increase of Internet traffic and the enormous bandwidth potential of all-optical transport networks based on wavelength division multiplexing, an IP-over-WDM network scenario is likely to be widespread in future communication networks. At the same time, IP networks are becoming more and more mission-critical. Hence, it is of paramount importance for IP-over-WDM networks to be able to recover quickly from frequently occurring network failures. This paper explains how multi-protocol label switching (both electrical and optical) recovery mechanisms can be important to reach that goal. Moreover, a novel MPLS recovery mechanism called fast topology-driven constrained-based rerouting is presented. Different MPLS recovery mechanisms are compared to each other. Special attention hereby goes to the additional capacity that is required to recover from frequently occurring failures.     

An optically clocked transistor array with dual serial-to-parallel and parallel-to-serial conversion capability for optical label swapping

We propose an optically clocked transistor array optoelectronic integrated circuit (OEIC) for both serial-to-parallel and parallel-to-serial conversion (demux/mux), enabling an interface between high-speed asynchronous burst optical labels and CMOS circuitry for optical label swapping. Dual functionality of the OEIC reduces size, power, and cost of the optical label swapper. The capability for greater than 20-Gb/s conversion operation is demonstrated.     

A concurrent two-layer restoration scheme for GMPLS WDM networks

Next generation backbone networks will likely consist of IP routers as well as optical cross connects (OXCs) and will deploy an optical control plane protocol. Generalized Multi Protocol Label Switching (GMPLS) has been proposed as the candidate of choice for the control plane. Optical fibers may carry large volumes of traffic and therefore adequate mechanisms must exist to enable the network to automatically recover from failures of fiber. In mission critical networks survivability becomes very important. We investigate the problem of autonomous recovery in such networks. The literature contains work in this area that investigates the problem of multilayer recovery. Such recovery had only been sequential in the sense that the published work recovers first in the optical domain, assuming the availability of redundant resources, and then proceeds to recover packet label switched paths. We report a recovery procedure for recovering packet label switch paths (packet LSPs) and lambda label switch paths (λLSP) concurrently. We have conducted an OPNET-based simulation study that compares the performance of the concurrent scheme with the previously published sequential two-layer recovery scheme. The study shows that the concurrent two-layer recovery scheme performs as much as forty-four percent faster than the sequential two-layer recovery scheme.     

An optical IM/FSK coding technique for the implementation of a label-controlled arrayed waveguide packet router

In this paper, we present a new concept of optical packet/burst switching suitable for generalized multiprotocol label switched (GMPLS)-based optical networks. In such networks, optical labeled switched paths are being established in a similar way as label-switched paths in MPLS. We use a wavelength label as well as an orthogonally modulated label, with respect to the payload modulation format, and which is encoded using either frequency-shift keying (FSK) or differential phase-shift keying (DPSK). Wavelength is used for switching in the node, whereas the orthogonal label defines the label-switched path. We present both simulation and experimental results to assess transmission performance of the proposed combined modulation scheme. In addition, we propose a suitable optical node architecture that can take advantage of this stacked label concept. Toward this, we use widely tunable wavelength converters to efficiently route IM/FSK (or IM/DPSK) optically labeled packets in an arrayed-waveguide grating (AWG)-based node structure. We present performance simulation results in terms of packet loss ratio and internal block probability. Internal blocking is an inherent problem of AWG optical routers, and a specific wavelength assignment algorithm has been developed to minimize it. Finally, the feasibility of IM/FSK transmission is experimentally demonstrated over an 88-km single-mode fiber span, and novel aspects of FSK generation and detection techniques are presented.     

On polarization sensitivity of all-optical label swapping using synchronous phase modulation

Polarization sensitivity degrades the performance of many optical devices in optical packet switched networks. We investigate the polarization sensitivity for all-optical label swapping for the first time. We propose and demonstrate a polarization-insensitive phase modulator for all-optical label swapping. The polarization sensitivity of the power penalty for the label swapping is less than 0.3 dB.     

Architectures and protocols that enable new applications on opticalnetworks

This article first discusses how advances in networking architectures and protocols can complement advances in optical communications research to increase the overall value of optical networks by enabling more applications. A review of existing optical networking solutions is then provided along with a classification of different types of optical networks. Finally, we show how single-hop and multihop wavelength-routed networks can be used efficiently for fast end-to-end file transfers when these networks are equipped with a hardware-implementable signaling protocol, a routing protocol, and a simple transport protocol     

Next-generation optical networks as a value creation platform

In this article we discuss the role of the next-generation optical networks and introduce enabling technologies that support network evolution. The role of networks is undergoing change and is becoming a platform for value creation. In addition to providing new services, networks have to accommodate steady traffic growth and guarantee profitability. We envision a next-generation optical network as the combination of an all-optical core and an adaptive shell operated by intelligent control and management software suites. Possible technological innovations are introduced in devices, transmission technologies, nodes, and networking software, which will contribute to attain a flexible and cost-effective next-generation optical network. New values will be created by the new services provided through these networks, which will change the ways we do businesses and go about our private lives.     

A 1+1 protection architecture for optical burst switched networks

High-capacity optical backbone networks protect their premium customers' information flows by routing two copies of the customer's data over disjoint paths. This scheme, known as 1+1 protection, provides extremely rapid recovery from network failures. We propose an architecture by which 1+1 protection can be extended to optical burst switched (OBS) networks. This architecture is designed by modifying the diversity routing architecture that was originally proposed for nonoptical packet networks and recently applied to networks employing the generalized multiprotocol label switched (GMPLS) architecture. We extend the architecture developed for just-in-time OBS signaling to support 1+1 protection. We also examine design issues that are raised by a difference in the propagation delays of the two disjoint paths across the OBS network. We show that a sufficiently large difference in the propagation delays can cause performance degradations that may result in an unsatisfactory quality-of-service on the protected connection. We examine the impact of this delay mismatch on restoration performance, probability of burst loss, and jitter. Through analysis and simulations, it is discussed how these negative effects can be eliminated.     

传送网络技术演进的思考

Driven by an ever-increasing number of new services and applications, transport networks have been undergoing significant changes. In this paper, we describe several exciting technology directions associated with future optical transport networks. We review the status of 100G, which is now commercially available and entering volume deployments, and its applications in China. Beyond 100G is considered as the primary technology for the expansion of both channel and fiber capacity in the near term, and several enabling techniques are introduced. Then, key technologies, products, and future evolutionary options of Optical Transport Networks (OTNs) are extensively discussed. Compared to fixed bandwidth and coarse granularity of current WDM network, a flexible grid architecture is a desirable evolu-tion trend, and key technologies and challenges are described. Finally, we illustrate the multi-dimension convergences in terms of IP and optical, Packet OTN (P-OTN), as well as Electronic Integrated Circuits (EICs) and Photonic Integrated Circuits (PICs). Transport networks are therefore in the process of be-coming more broadband, robust, flexible, cost-effective and lower-power-consumptive.     

Reliable Multipath Provisioning for High-Capacity Backbone Mesh Networks

We investigate reliable multipath provisioning of traffic in high-capacity backbone mesh networks, e.g., next-generation SONET/SDH networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths, a feature that may lead to significantly improved performance over conventional single-path provisioning. Other mesh networks such as those employing optical wavelength-division multiplexing (WDM) and multiprotocol label switching (MPLS) can also benefit from this multipath provisioning approach. We propose effective multipath bandwidth as the metric to provision a connection while satisfying its reliability requirements (measured in terms of availability). We demonstrate that effective multipath bandwidth provides more flexibility and lower blocking probability without the cost and the complexity associated with traditional protection schemes developed for optical WDM and MPLS networks. We also investigate the practical problem of provisioning effective multipath bandwidth with cost constraints. We analyze the tractability of the problem and present a heuristic which results in significantly reduced number of blocked connections due to cost constraints.     

支持区分服务的全光网络设计和实现

随着光层业务对传送服务质量的要求趋于多样化以及全光网络的智能化演进，光服务等级协定被提出。为了适应各种业务的不同传送需求，未来的光网络碰具有支持区分服务的能力。在多业务环境下。处理好满足业务的不同服务需求和优化网络资源之同的矛盾。需要传送网络流量工程各个功能子模块具有集成多种实现机制的能力，从而在光层实现区分服务的集成化。目前，支持区分服务的光网络流星工程方案还只是研究领域的成果，需要对现有控制平面的协议进行扩展和标准化，从而使光服务等级协定走向实用。     

Demonstration of all-photonic spectral label-switching for optical MPLS networks

All-photonic label-switching of weight four spectral packet labels (concurrent quadruple wavelength conversion) is demonstrated for optical multiprotocol label-switching networks. The experimental setup is based on cross-gain modulation in a fiber ring laser using a semiconductor optical amplifier gain medium and uses commercially available components. Static transfer functions and step response measurements for various input-output label-switching combinations show that a noisy input label with small extinction ratio can be switched to a clean, amplified, output label.     

Framework for MPLS-based control of optical SDH/SONET networks

The suite of protocols that defines multiprotocol label switching is in the process of enhancement to generalize its applicability to the control of optical networks. One area of prime consideration is to use these generalized MPLS protocols in upgrading the control plane of optical transport networks. This article describes those extensions to MPLS directed toward controlling SDH/SONET networks. SDH/SONET networks are ideal candidates for this process since they possess a rich multiplex structure, and a variety of protection/restoration options are well defined and widely deployed. We discuss the extensions to MPLS routing protocols to disseminate information needed for transport path computation and network operations and the extensions to MPLS label distribution protocols needed for provisioning of transport circuits     

All-Optical Label Swapping of Scalable In-Band Address Labels and 160-Gb/s Data Packets

Scalability and photonic integration of packet switched cross-connect nodes that utilize all-optical signal processing is a crucial issue that eventually determines the future role of photonic signal processing in optical networks. We present a 1 $times$ 4 all-optical packet switch based on label swapping technique that utilizes a scalable and asynchronous label processor and label rewriter. By combining $N$ in-band labels at different wavelengths (within the bandwidth of the payload), up to $2^{N}$ possible addresses can be encoded. The proposed label processor requires only $N$ active devises to process the $2^{N}$ addresses that makes this label processing technique scalable with the number of addresses. Experimental results showed error-free packet switching operation at 160 Gb/s. The label erasing and new label insertion operation introduces only 0.5 dB of power penalty. These results indicate a potential utilization of the presented technique in a multi-hop packet switched network.