Optical amplification and dense wavelength division multiplexing (DWDM) have fundamentally changed optical transport networks. Now that these technologies are widely adopted, the bottleneck has moved from the outside line plant to nodal central offices, where electrical switching equipment has not kept pace. While OEO technology was (and still is) necessary for grooming and traffic aggregation, the transport network has dramatically changed, requiring a dramatic rethinking of how networks need to be designed and operated. While todays transport networks carry remarkable amounts of bandwidth, their optical layer is fundamentally static and provides for only simple point-to-point transport. Efficiently managing the growing number of wavelengths can only be achieved through a new breed of networking element. Photonic switching systems (PSS) can efficiently execute these functions because they are bit rate, wavelength, and protocol transparent. With their all-optical switch cores and interfaces, PSS can switch optical signals at various levels of granularity wavelength, sub band, and composite DWDM fiber levels. Though cross-connect systems with electrical switch cores are available, they perform these functions at very high capital costs and operational inefficiencies. This paper examines enabling technologies for deployment of intelligent optical transport networks (OTN), and takes a practical perspective on survivability architecture migration and implementation issues.

It is believed that on-demand dynamic lightpath provisioning will enable service providers to respond quickly and economically to customer demands. One of the challenges involved in designing wavelength-routed networks with dynamic traffic demands is to develop efficient algorithms and protocols for establishing lightpaths. This paper proposes a novel dynamic path-selection algorithm that combines service path link using probability weight with efficient disjoint-path restoration bandwidth sharing to obtain a balanceable traffic distribution during the wavelength route selection, and consider the wavelength bandwidth capability sharing between the disjoint paths for the failure scenario. At the same time, to realize dynamic lightpath establishment, this paper discusses the strategy of lightpath establishment based on Automatically Switched Optical Network (ASON), and also presents the extension of GMIPLS protocols to efficiently collect and distribute the necessary information in ASON architecture frame. Through the distributed IP-centric protocol we can realize link state update and dissemination. To sum up, in this paper we hope to show a full and efficient dynamic path establishment mechanism with ASON control plane function and GMPLS principle.

Optical transport service providers need control and optimization strategies for wavelength management, network provisioning, restoration and protection, allowing them to define and deploy new services and maintain competitiveness. In this paper, we investigate a game theory based model for wavelength and flow assignment in multi wavelength optical networks, consisting of several backbone long-haul optical network transport service providers (TSPs) who are offering their services -in terms of bandwidth- to Internet service providers (ISPs). The ISPs act as brokers or agents between the TSP and end user. The agent (ISP) buys services (bandwidth) from the TSP. The TSPs compete among themselves to sell their services and maintain profitability. We present a case study, demonstrating the impact of different bandwidth broker demands on the supplier's profit and the price paid by the network broker.

With the recent explosive growth of Internet traffic, optical networks with high connectivity and large capacity are indispensable. This can be achieved by multi-dimensional optical routing networks, which can offer fine bandwidth granularity and a large number of channels. In this paper, a trunk switched model is used to study the performance of multi-dimensional optical routing networks. The closed-form network utilization is derived and compared to that of one-dimensional optical routing networks. The network utilization gain is found to be closely related to the link correlation and be insensitive to the network size. Besides, based on this analytical model, the closed-form conversion gains are derived for both partially and fully convertible cases. These results provide crucial information in performance optimization of multi-dimensional optical routing networks.

A graphical simulation system for the study of the physical performance of optical packet switching (OPS) nodes is accomplished. With the simulation system, the effect on bit error rate (BER) performance caused by a variety of factors, such as the crosstalk parameters of OPS nodes, numbers of cascaded OPS nodes, the length of optical output buffer, the traffic load, the amplitude fluctuation and the delay fluctuation of optical signals, are simulated and studied. The reliability of the simulation system is proved by the agreement between simulation results and analytical results

This paper proposes a novel buffer scheduling algorithm, which considers offset time for burst control packet in optical burst switching (OBS) WDM networks. In the proposed algorithm, a burst control packet (BCP) with short residual offset time is served by the scheduler prior to a BCP with long residual offset time. Our proposed scheme can decrease the data loss due to early arrival problem of the data burst in OBS networks. Finally, we evaluate the performance improvement through the simulation.

For support of multimedia applications in Internet, at least four service classes are normally outlined. We expect optical packet switching to be of special interest in terabit capacity networks with a high number of wavelengths. Our analysis shows that when the wavelength dimension is used for contention resolution, and number of wavelengths is 32 or higher, node-delay is negligible. However buffering in optical packet switches is a scarce resource which use should be minimized. Based on the requirement of the future network, and on our packet switch performance analysis, we suggest reducing the number of service classes to two: A normal class (NCT) with medium low packet loss and a low need for buffering, and a high class (HCT) with a minimum of packet loss. Performance of a buffer reservation scheme is analyzed by simulation. Assuming the network of today with 10 % HCT traffic, assigning four buffer inputs to the HCT traffic, a difference in optical packet loss ratio of three orders of magnitude can be obtained. The same difference in optical packet loss ratio can be obtained if 50 % HCT traffic is assumed (network of tomorrow), by assigning a higher number of buffer inputs.

Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over WDM. In this paper, we describe the basic concept of OBS and present a simulation model. The objective of our simulation is to estimate the throughput and the burst loss probability in such a network of OBS nodes. The traffic characteristics and reservation schemes are essential on burst loss probability. We give some comparison of these schemes by using our simulation model, as we can see, while low self-similarity traffic distribution and JET (just enough time) reservation schemes may have a potential positive effect on the overall blocking probability of the OBS network.

This paper reviews the current status of various optical monitoring techniques for DWDM networks. The parameters to be monitored include optical frequency, signal power, optical signal-to-noise ratio, and optical path, etc.

Today, Wavelength Division Multiplexing (WDM) transmission systems are deployed extensively in transport networks. They are used mainly for static point-to-point connections. With the availability of fast reconfigurable Optical Cross Connects (OXC) and the introduction of a control plane in the Optical Transport Network (OTN), optical channel based logical networks can be built for dynamic WDM networks. Resilience in current transport networks is mainly based on static SONET/SDH dedicated and shared protection. Distributed control planes allow new, flexible protection mechanisms (e.g. GMPLS reroute and fast reroute). To evaluate future distributed control concepts and new resilience schemes in transport networks, we have implemented a dynamic OTN simulation model. Several case studies have been performed using different protection and restoration methods. Different failure scenarios (single or multiple link failures) were used. The paper evaluates the case studies in terms of scalability, recovery time criteria, capacity use (efficiency) and availability. It is shown that the new and flexible resilience schemes are a promising alternative to traditional statically preplanned protection in transport networks. Furthermore, they provide increased network availability in multiple failure cases.

This Paper presents a Priority Based Recovery Scheme (PBRS) improving the utilization of limited resource- i.e. light-paths- which is necessary when recovery mechanism occurred in the IP Over Optical Networks. PBRS is used in the RLG (Recovery Link Group) made by priority number of LP (Light path). We assumed there are three kinds of LPs by their traffic characteristics Mission-Critical, Best-Effort and Low-priority -in the RLG. When the LP faults are detected, primary LPs classified by the order of traffic priority choose recovery mechanism by their priority number value. In the priority based RLG, Each LP has its own recovery mechanism priority 1 LP (Mission-Critical traffic) use dedicated protection scheme, priority 2 LP (Best-effort traffic) uses preplanned restoration scheme and Priority 3 LP (Low-Priority traffic) uses dynamic restoration scheme. After recovery mechanism is accomplished, new LP Setup information based on the given priority information is transferred to ingress OXC (Optical Cross Connect) for the purpose of making new light path. OXC has structure capable of making new light paths or releasing light paths via signaling control to maintain consistent recovery capability, regardless of fault count, based on priority scheme. The PBRS has some advantages expanding availability of LPs that is limited resources in the optical network and designing the network that has consistent recovery capability. In this paper, we also present a Router and OXC structures, LP failure detection mechanism, and signaling procedures that are necessary to adopt PBRS. The performance and effectiveness of PBRS is demonstrated by means of statistical simulations on randomly generated mesh network topology.

In IP over WDM networks, when a failure (a link failure) occurs, the service restoration can be implemented by dynamic routing in IP layer. But it needs the virtual topology remains connected after any physical link failure. Otherwise, IP layer cannot find an alternate path to restore the service. The problem of routing logical links (lightpaths) on a physical network in a way that the logical topology remains connected in the event of single physical link failure is called survivable routing. Our aim is to find out the minimum wavelength requirement for survivable routing. In short, we address the survivable routing problem by proposing a new ILP algorithm which works well with sparse-connected logical topologies. The necessary and sufficient conditions for survivable routing are simplified, which greatly reduces the number of survivable constraints. Based-on the simplified conditions, a new ILP formulation with K-shortest paths as alternate paths for a logical link is presented, which mainly reduces the number of variables needed to be solved. It will be demonstrated that the time needed to solve such an ILP is relatively small. Finally, numerical results are given and discussed to show the effectiveness of our algorithm.

A Wavelength Division Multiplexing (WDM) network offers a flexible networking infrastructure by assigning the route and wavelength of optical transparent channels (also known as lightpaths). We can construct an optimal logical topology, by properly setting up the lightpaths. Furthermore, setting up a backup lightpath for each lightpath improves network reliability, i.e., tolerance against failures of network components. Most studies on methods to design a logical topology provide optimization formulations (e.g., Mixed Integer Linear Problem) and their solutions under the assumption that the traffic requirements are known in advance. In practice, traffic demand changes due to new services. When it does, a new optimal (or sub-optimal) topology should be obtained by again applying the formulation. Then, we can reconfigure the running topology to the logical topology obtained. However, during this reconfiguration, traffic loss may occur due to the deletion of older lightpaths. In this paper, we consider reconfiguring the logical topology in reliable WDM-based mesh networks, and we propose five procedures that can be used to reconfigure a running lightpath to a new one. Applying the procedures one by one produces a new logical topology. The procedures mainly focus on utilizing free wavelength resources and the resources of backup lightpaths, which are not used usually for transporting traffic. The results of computer simulations indicate that the traffic loss is remarkably reduced (in the worst case, more than 50% reduction in traffic loss) in the 14-node network we used as an example.

Optical performance monitoring is an import issue for the design, operation and maintenance of optical transport networks (OTN). Pilot tone detection is one of the monitoring techniques used in all-optical WDM networks [1]. This technique is very simple and could monitor both the optical paths and switch failures in a large-scale WDM transport networks. But the effect of Stimulated Roman Scattering (SRS) could product ghost tone that will suppress the capability of pilot-tone based monitoring technique. We give a simple model to analyze the effects of Stimulated Raman Scattering on pilot-tone base WDM supervisory technique.

The paper considers the performance as well as the effectiveness of multi-token based access protocol for supporting IP over WDM ring network. Both normal ring topology and multi-connected distributed loop such as wheel topology are considered for network simulation and performance optimization.

Link management protocol (LMP) is proposed in generalized MPLS in order to manage the links between adjacent nodes. IETF specifies four basic functions in relevant drafts: control channel management, physical connectivity verification of the data links, link property correlation, downstream alarms and link failure localization. In this paper we discuss LMP and bring forward two new functions: link protection and restoration, and service-relational links. The extension makes the optical network more reliable and more flexible to different kinds of services.

Optical label processing including optical SCM label reading, writing, erasing and transmitting is discussed in this paper. Optical erasing based on a proposed Lylot-Sagnac filter is investigated experimentally. And transmission performance of the SCM label is also analyzed.

Photonic networks using Optical Burst Switching (OBS) emerged as an attractive choice for building the next generation Photonic Internet. In burst switched photonic networks, contentions caused by multiple bursts intending to use the same wavelength of the same link at the same time, remarkably increase burst dropping probability and degrade network throughput. As efficient contention resolution methods, the previously presented deflection routing and priority-based wavelength assignment (PWA) work individually but are not compatible with each other. It is therefore desirable to combine these two methods together to make further performance improvement. In this work, we revamped PWA to support deflection routing and show the improved performance of deflection routing-compatible PWA through simulation results.

Optical Internet carries IP traffic over a WDM optical network by taking advantage of huge bandwidth of optical network. The optical burst switching (OBS) was proposed to enhance the low utilization problem of a wavelength routing (or optical circuit switching) and at the same time, relax the technical difficulty in implementing optical packet switching. The optical burst switched networks consists of the edge routers and the core routers. In particular, the edge routers perform the adaptation function, which interfaces between the electronic layer (IP, ATM, SONET) and the optical layer (OBS networks). One of the key functions of the edge router is the burst assembly, in which the data from the electronic layer assembled into a super packet (called a burst). In this paper, we compare three burst assembly schemes: constant assemble time (CAT), variable assemble time (VAT), and adaptive assemble time (AAT). The performance of burst assemble schemes are compared based on the extensive simulations.

To deliver reliable differentiated services in optical networks, GMPLS requires a set of procedures to provide protection for the traffic carried on the light paths. In this paper we propose a hierarchical path protection mechanism that is simple, scalable, fast, and efficient. We describe in detail our design considerations, the communication of fault information to appropriate forwarding or/and switching elements, and the fault detection protocol. In particular, we propose a new notification protocol for efficient and fast distribution of fault notification messages. A new Hierarchical Path Protection (HPP) improves the utilization of network resources- Label Switched Paths (LSPs) such as Electrical LSP (E-LSP), Lambda-LSP (L-LSP), WaveBand-LSP (WB-LSP), Fiber-LSP (F-LSP), bandwidth etc.- that are necessary when recovery mechanism occurred in the GMPLS networks. The HPP is used in the multiple-layer networks made by priority number of paths. We assume that there are three kinds of priorities on LSPs by their traffic characteristics of multimedia services, real time, mission-critical and best-effort services in the GMPLS networks. When the faults of LSPs are detected, primary LSPs classified by the priority of multimedia traffic choose recovery mechanism according to their priorities. In the priority based LSPs, each LSP has its own recovery mechanism that the LSP of priority 1 (real-time traffic) has the dedicated protection scheme, the LSP of priority 2 (mission-critical traffic) has the preplanned restoration scheme and the LSP of priority 3 (best-effort traffic) has the dynamic restoration scheme. After recovery mechanism is accomplished, the information for setting up on LSP based on the given priority is transferred to the ingress Optical Cross Connect (OXC) for the purpose of making new LSP. The OXC has the structure capable of setting up new LSPs or releasing LSPs via a signaling to maintain the consistent recovery, regardless of fault count, based on the priority scheme. The HPP has some advantages expa

A new structure for star shaped ring networks that features high-speed channel bit-rate and long communication distance is demonstrated. A novel protection scheme using narrow range tunable laser diode is successfully implemented in this architecture.

ABSTRACT A major challenge of survivable wavelength-division multiplexing (WDM) network design is deciding how much spare capacity there should be and where it should be placed, so that interrupted traffic can be recovered within a very short time. Protection, including link protection and path protection, is the main way to solve this problem and to prevent huge losses. Link protection and dedicated path protection currently dominate this fault recovery field. Both have short recovery time and low resource efficiency. Shared path protection is also resource efficient with acceptable recovery time. More and more industries recognize that shared path protection is the trend and are trying to find good methods to design shared protection paths. This paper proposes a new efficient algorithm-Predetermined Protection Path Design (PPD), which can design maximum sharing protection paths. We describe in detail how PPD works, and compare it with the existing protection algorithms. Simulation results show that PPD can design maximum sharing protection paths and achieve 28% better resource efficiency than dedicated path protection as well as 12% better resource efficiency than the current shared path protection algorithms, with acceptable recovery time. PPD also has good generality, scalability and restorability.

In a wavelength-routed WDM optical network, having regeneration and wavelength conversion at every node is not cost-effective. However, in a nation-wide backbone network, regeneration is required for some lightpaths. With shared-mesh protection, wavelength-conversion is helpful in increasing the wavelength sharing among protection paths therefore can improve resource-utilization. In this work we study the problem of selecting wavelength-conversion and regeneration sites in such a network. We show that the wavelength converter placement problem can be formulated as an integer linear program and propose several heuristics for solving the sparse wavelength conversion and regeneration problem.

According to the previous researches, all-optical converters based on FWM and XGM conversion schemes at present are well suited for system use. Both performances of optical networks with FWM and XGM conversion are examined in this paper. From the results, we find that the benefit obtained by full range conversion can be achieved by using FWM conversion with the degree of conversion d=1 or 2, when the number of wavelengths on a fiber is small. But with the increase in number of wavelengths, higher conversion degree is required to achieve the performance of full range. As for the case of XGM conversion, our results show that the performance of XGM is worse distinctly than full range conversion because of its asymmetric conversion, no matter the number of wavelengths is large or small. In order to improve the performances of the networks with limited range conversion in the case of large number of wavelengths, three simple wavelength assignment algorithms (FUWC, LUWC and MSW) are proposed. We apply these algorithms to the case of Ring and Mesh-torus. Through simulation, we find that our algorithms do greatly reduce the blocking probabilities of networks with limited range conversion.

A novel multistage optical cross-connect (OXC) that combined the advantages of three technologies of Space Division Switching (SDS), Wavelength Division Switching (WDS), and Optical Time-Division Multiplexing (OTDM) has been proposed. The structures of the first and second stages of a 2 X 2 and a 4 X 4 OXC have been presented. By means of the splitter and delivery (SAD) switch, it is cost-effective and fully modularized and very convenient to scale to n X n OXCs suitable for large-scale backbones.

Internet backbone network is undergoing a large-scale transformation from the current complex, static and multi-layer electronic-based architecture to the emerging simplified, dynamic and single-layer photonic-based architecture. The explosive growth in the Internet, multi-media services, and IP router links are demanding the next generation Internet that can accommodate the entire traffic in a cost-effective manner. There is a consensus in current industries that IP over WDM integration technologies will be viable for the next generation of the optical Internet where the simplified flat network architecture can facilitate the networking performance and the networking management. In this paper, we firstly propose a novel node architecture-Terabit Optical Router (TOR) for building the next generation optical Internet and analyzes each key function unit of TOR including multi-granularity electrical-optical hybrid switching fabrics, unified control plane unit and so on. Secondly, we discussed the unified control plane unit of TOR in detailed Thirdly we describe our cost vs. performance analysis for various application of TOR. According to our evaluation carriers can get a cost reduction of more than 60 percent by using the TOR. Finally, we reach conclusions that TORs rather than OBS or BFR(Big Fat Router) routers, a cost effective multi-granularity switching and routing technique, are feasible to build the next generation Internet.

Blocking has been the key performance index in the design of an all-optical network. Existing research demonstrates that an effective routing and wavelength assignment (RWA) strategy and a proper wavelength converter placement algorithm are the two primary vehicles for improving the blocking performance. However, these two issues have largely been investigated separately in that the existing RWA algorithms have seldom considered the presence of wavelength conversion, while the wavelength converter placement algorithms have largely assumed that a static routing and random wavelength assignment algorithm is employed. In this paper we present some strong evidences that these two issues need to be considered jointly, and call for the re-examination of both RWA and wavelength converter placement. This article is divided into two parts. First we demonstrate that the conventional RWA algorithms do not work well in the presence of wavelength conversion since they usually only take into consideration the distribution of available wavelengths, and do not explicitly consider the lengths of routes. Through extensive simulation over a variety of topologies, we demonstrate that a weighted least-congestion routing and first-fit wavelength assignment (WLCR-FF) RWA algorithm can achieve much better blocking performance than static routing, fixed-alternate routing, or least-loaded routing algorithms in the environment of sparse or full wavelength conversion. Secondly, using simulation we show that a heuristic-based converter placement algorithm called Weighted Maximum Segment Length (WMSL) algorithm proposed for a simple dynamic RWA (i.e., the least-loaded routing algorithm) under sparse wavelength conversion, not only outperforms existing wavelength converter placement algorithms by a large margin, but also can achieve almost the same performance as that of full wavelength conversion using the same RWA algorithm.

Traditional approaches to wavelength routing network design divide it into two separate problems: virtual topology design (VTD), in which best connections among nodes are derived from traffic demand, generating requests for connections; and routing-and-wavelength assignment (RWA), in which physical paths are accommodated in the physical topology to support the requested connections. This separation is necessitated by complexity, but it is suboptimal and will only yield the best static solution. For the case of dynamic traffic, one needs to set up a connection for each request as it arrives, and the lightpath is released after some finite amount of time. The routing and wavelength assignments must then preserve enough open capacity to avoid blocking of future requests. Several algorithms have been proposed for this purpose. We consider a loose topology, in which static and dynamic traffic demands share the physical resources of the network. For this purpose, the static assignment problems (VTD and RWA) are solved so that blocking probability is minimized for the dynamic traffic while minimum performance objectives are met for the static demand. The proposed strategy entails the use of the dynamic RWA heuristics to guide the solution of the static VTD/RWA problem.

Fixed routing is favoured because it simplifies physical layer engineering, such as link budget calculations. The use of the fixed routing scheme can achieve fast bandwidth provisioning at the expense of inferior network blocking performance and lack of adaptability to traffic variation. In this paper, a load-balanced fixed routing scheme is proposed. For each source-destination pair, it assigns a fixed path such that the load-balancing requirement is met. This scheme is formulated into an Integer Linear Programming process. Both simulation and analytical methods are used to verify the effectiveness of the proposed planning algorithm. We also modify an analytical model of blocking probability by considering the load-balancing characteristic.

This paper describes a simple parallel signaling protocol for connection management in ASON. The signaling procedure is discussed in detail and the signaling time is tested experimentally and compared to hop by hop signaling protocols. The result shows that the new proposal has a better time performance than the traditional protocols.

The network architecture where each node integrates an IP router and an OXC (optical cross-connect) is an attractive paradigm for the next generation optical Internet. LP wavelength routing or POW (packet over wavelengths) is based on this kind of architecture. The goal of this architecture is to switch as much traffic as possible directly by means of OXCs, because IP forwarding is relatively expensive and causes large end-to-end delay by comparison. Based on analyzing the problems and shortcomings of the previous node structure, a novel node structure is proposed to overcome the problems encountered by the previous scheme. Then two IP switching protocols, IFMP (Ipsilon Flow Management Protocol) and GSMP (General Switch Management Protocol), are extended to support [P wavelength routing networks. Finally, the performance of an IF wavelength routing network is analyzed with self-similar network traffic model. The simulated results show that the higher the network traffic self-similar degree, the higher switching gain the network gets.

Multi-protocol label switching (MPLS) technology is useful for IP Virtual Private Networks (IP-VPNs), guaranteeing bandwidth in IP (Internet Protocol) networks, and carrying out traffic engineering with explicit routing. The advantage of MPLS is its high capability to achieve of reliable networks when used with Fast Rerouting. However, Fast Rerouting requires a lot of network resources. This is because, for the rapid recovery of end-to-end communications after detection of failures, secondary LSPs must already have been reserved as detours in case there are failures on primary node-to-node links. The sharing of bandwidth among secondary LSPs is thus significant as a way of reducing the usage of network resources when Fast Rerouting is applied. In this paper, we propose a new routing algorithm in which bandwidth is shared among the secondary LSPs for multiple primary LSPs. This algorithm produces efficient network-level LSP designs. Three approaches to the dynamical changing of Open Shortest Path First (OSPF) link-cost metrics are applied in the algorithm. Each approach improves efficiency in the sharing of LSPs. The approaches are (1) the broader distribution of primary LSPs to reduce the need for detours in cases of single failures, (2) the concentration of secondary LSPs on links to increase the possibilities for bandwidth sharing, and (3) the distribution of secondary LSPs that cater to a certain failure, thus increasing the numbers of detouring LSPs which are independent of each other on the respective links. The scheme provides a slight improvement over the results of the conventional Dijkstra-algorithm calculation which is used in conventional OSPF. The proposed algorithms are applied with various network models that have been proposed in IETF Internet drafts, e.g.,

The Shared Risk Link Groups (SRLG) concept is an extension of physical-disjoint, e.g. link/node-disjoint. It is defined as a group of links that share a common risk component whose failure can potentially cause the failure of all the links in the group. SRLG can be identified by a SRLG identifier. Different SRLG identifiers can be assigned to each link by network administrator in optical Traffic Engineering (TE) to satisfy connection's reliability requirement. A dependable connection can be achieved by establishing two SRLG-disjoint paths. A new dynamic integrated routing algorithm for shared path-protection based on SRLG-disjoint is presented in this paper. It provides the same level of protection against single SRLG failure as dedicated path-protection scheme. Moreover it is superior to dedicated path-protection scheme in network utilization. Network performance, based on dynamic traffic with different load, is investigated via simulations. The results show that the scheme can improve the performance of the network significantly.

This paper investigates the diverse routing in a wavelength division multiplexing (WDM)-based optical network under SRLG-disjoint constraints. In operational optical networks there are a lot of traffic flows within every lightpath. Any failure of one Iightpath will lead to a great loss. So we should provide path protection for the working lightpath. The concept of Shared Risk Link Groups (SRLG) is introduced in optical networks by IETF, which is defined as a group of links that share a common risk component whose failure can potentially cause the failure of all the links in the group. This concept groups all of the entities, such as wavelengths and links, etc., that are affected by a single failure. Now when path protection is employed, for any lightpath connection request, we compute two SRLG-disjoint lightpaths, one as working path and the other as protection path. There are some literatures, which propose methods for link-disjoint paths pair or node-disjoint paths pair, but few algorithms for SRLG-disjoint paths pair. The SRLG-disjoint constraints entail the general constraint-based path computation algorithms. Since this problem is an NIP-complete problem and there is no algorithm which could be used to solve this path computation in polynomial time. This paper presents a heuristic algorithm, Low-cost Pair of SRLG-Disjoint Paths Algorithm (LPSD), to solve this problem. LPSD can compute two SRLG-Disjoint paths simultaneously, and the total cost of the two paths is near optimal. Analysis and simulation are also given out.

All-optical networks require end-to-end lightpaths to be established for traffic to flow. Given that there are no wavelength converters present in the network, each lightpath only accommodate a single wavelength. It is shown that as the lightpaths traverse more hops, the blocking probability increases.This is causes the Fairness Problem. We introduce the Traffic Classification and Service Method (ClaServ), which optimizes the Fairness Problem, as well as reduce the traffic blocking probability when the networks require lower blocking probability. The combination of the Waveband Access Range (WAR) and the Waveband Reservation (WRsv) methods changes the traffic's distribution among the wavebands on each link of the path to control the degree of the interference among the classified traffic. Under certain traffic load, by setting the range of accessible wavebands and reserved wavebands for classified traffic, the network can achieve both the fairness and low blocking probability for all type of traffic. The simulation results show that for a 4x4 Mesh-Torus network the ClaServ method can greatly reduce the blocking probability for longer lightpaths by a factor of 100. It is also described how the ClaServ method can easily be implemented into a distributed signaling protocol.

In order to improve the processing ability in the switching node, a lot of optical packet switching schemes were proposed, one of them is multi-wavelength label switching. In the scheme, a case of using K bit-long label and W different wavelengths can obtain WK unique labels at most. Here A novel label-coding scheme was put forward, which can produce more labels than before, For an example, if using 2 bit-long label and 2 different wavelengths, we can get 9 different labels, instead of 4 different labels using the old coding method proposed in the paper. At last, we give the design of the transceiver in detail.

Optical burst switching (OBS) is a promising solution for realizing IP over WDM since it combines the advantages of optical circuit switching and optical packet switching (OPS) while overcoming their shortages. In this paper, the mechanisms to implement burst assembly and scheduling in an OBS edge router are discussed. The performance of the output traffic from the edge router, e.g. traffic shape and delay, is analyzed with simulation results. The results show that the traffic shape and the delay are affected by maximum delay specified by different classes of services, the maximum length of the burst, the burstiness of the traffic, and the mechanisms of burst assembly and scheduling. By properly designing, the traffic shape can be improvement while the delay keeping in the bounds.

This paper presents a routing and wavelength assignment for survivability (RWAS) algorithm in optical networks. The attentions of most previous RWA algorithms focus on traffic balance, blocking performance, and network resource utilization, which are key performances of optical networks. However, with the development of DWDM systems and the increase of traffics in optical network, services survivability and network survivability must be paid much more attentions to. RWAS considers services survivability while routing and assigning wavelength(s) for a set of connections, which perhaps has not better resources utilization and blocking performances, but assures that as many service connections as possible can be restored in the current network in the case of any single link failure.

As many kinds of media converge to the Internet, the backbone will face new demands not only in terms of bandwidth, but also in terms of services. Therefore it is certain that Internet will evolve into IP-over-WDM based all-optical network. Obviously, the optical router will be a crucial network device. In the paper, we propose a practical architecture of optical router. Based on all-optical labeled burst switching, this architecture supports all-optical edge-to-edge data routing and transport services with transparent data rate and format, and simplifying protocol and operations. From the viewpoint of practicality, some key issues during the design have been studied and analyzed, and corresponding feasible solutions to them are put forward respectively. Finally an experimental system and results are shown.

A diffuse hologram was designed, fabricated and tested. The application of this hologram is to create a uniform light distribution environment so that shadowing problem encountered in infrared-red communication could be overcome. Our hologram is a binary-phase level with an array of pixel of 256 x 256 and was computer generated. The hologram was fabricated using both the direct laser writer and electron beam writer technique, and followed by reactive ion etching on quartz substrate. The feature size of the holograms is ~11 mm and ~2 mm for the direct laser writer and e-beam lithography respectively. To evaluate the hologram, it was reconstructed in a dark room of size 4.6m x 3.6m x 2.61m and light distribution across the room was measured.

n this paper, we propose a G1VIPLS-based unified traffic engineering scheme in optical networks to cooperate at both optical layer and IP/MPLS layer achieving high efficiency of resource utilization. In WDM networks, end-to-end all-optical paths, called lightpath, can be setup between two edge optical routers. The set of lightpath comprise of the logical topology of optical networks. In IP/MPLS layer, a LSP is established on the logical topology. With the traffic increasing or decreasing, it is expected that the logical topology can adapt to traffic changes. When the traffic in a lightpath increases and becomes extremely heavy, allotting a new lightpath can partition some traffic and relieve the congestion. On the contrary, when the bandwidth utilization in a lightpath is very low, the lightpath may be released to free up its occupied resources. Based on this idea, a topology-adaptive scheme is proposed and two adjustable thresholds are introduced which are employed to control the frequency of lightpath setup or release. Finally, several key issues in unified traffic engineering are presented

Generalized multiprotocol label switching (GMPLS) has emerged as a very promising technology for the next generation carrier networks. GMPLS successfully combines the best features of IP and ATM in terms of QoS, privacy, flexibility and scalability. Besides, GMPLS introduces enhancements to the existing IP routing and signaling protocols by supporting not only networks that perform packet switching (IP), but also networks that perform switching in the time (TDM), wavelength (DWDM), and space domain (circuit switching). This paper discusses the design and implementation of a simulation-based GMPLS Optical Router (GOR). We build our GOR model on OPNETtm platform with all the necessary GMPLS functionalities of an optical backbone router, for the GOR to behave as a virtual machine. The description on the essential design features and the key implementation elements of the internal mechanism of GOR form the highlight of this paper. Our virtual GMPLS Optical Router has the capability of giving a more integrated and realistic simulation on wavelength routing, wavelength assignment, wavelength switching, dynamic label switching path (LSP) setup, distributed routing table calculation, and blocking mechanism of GMPLS light paths, all within a scenario. Our simulation results include the blocking rate, which is highly comparable to a real GMPLS optical network. In addition, our proposed GOR is able to provide a simulation platform for further development and future enhancement of GMPLS technologies.

Transmission performance of the optical label with the double-sideband subcarrier multiplexing is investigated using Volterra transfer function approach. It is shown that the phase shifts of the two sideband signal is induced jointly by the interaction between SCM component and payload component due to fiber dispersion and nonlinearity. This will cause the SCM label fading, and then harm to system performance.