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Whispering gallery mode resonators have been demonstrated to be a great way to achieve superior optical cavities with high quality factor and small mode volume. However, due to the high sensitivity of these modes to the properties of the resonator boundary, they are susceptible to parasitic splitting of clockwise and counterclockwise modes. In this work, we investigate the effect of implantation of an engineered notch into the boundary of a circular microdisk resonator fabricated from colloidal quantum dots, which are particularly sensitive to boundary defects. We observed a strong reduction of parasitic mode splitting with introduction of a large engineered notch, as well as enhanced directionality of laser emission. We further investigate the performance of these resonators in evanescently coupled pairs, where the modal interaction allows modulation of laser behavior through variation of the gain and loss induced by the optical pump. We show that two distinct cases of modal interaction can be achieved by adjusting the size of the engineered notch, providing a bridge between intra- and interdisk modal interactions for laser spectral control.

We present a real-time Truncated Signed Distance Field (TSDF)-based three-dimensional (3D) semantic reconstruction for LiDAR point cloud, which achieves incremental surface reconstruction and highly accurate semantic segmentation. The high-precise 3D semantic reconstruction in real time on LiDAR data is important but challenging. Lighting Detection and Ranging (LiDAR) data with high accuracy is massive for 3D reconstruction. We so propose a line-of-sight algorithm to update implicit surface incrementally. Meanwhile, in order to use more semantic information effectively, an online attention-based spatial and temporal feature fusion method is proposed, which is well integrated into the reconstruction system. We implement parallel computation in the reconstruction and semantic fusion process, which achieves real-time performance. We demonstrate our approach on the CARLA dataset, Apollo dataset, and our dataset. When compared with the state-of-art mapping methods, our method has a great advantage in terms of both quality and speed, which meets the needs of robotic mapping and navigation.

Evanescently coupled pairs of microdisk lasers have emerged as a useful platform for studying the non-Hermitian physics of exceptional points. It remains an open question how scalable and versatile such phenomena can be when carried over to other designs. Here we have studied the effect of gain/loss modulation in an evanescently coupled pair of microdisk optical resonators fabricated from solution-processed colloidal quantum dots. The emission spectra of these structures are sensitive to small imperfections, which cause frequency-splitting of the whispering gallery modes. Despite this inherent disorder, we found that when spatially modulating the optical pump to vary the gain differential between the coupled microdisks, the coupling drives the split parasitic intra-cavity modes into coalescence at an exceptional point of the resulting three-mode system. This unusual behavior is rationalized via a Hamiltonian that incorporates the intra-cavity coupling as well as the anisotropic inter-cavity coupling between modes in the microdisk pair., Pairs of microdisk lasers are one of the most common systems for studying optical PT-symmetry. Here, Lafalce, Zeng et al. study the influence of fabrication imperfections in a disk pair made from colloidal quantum dots and show that the resulting three modes also coalesce at an exceptional point.

Microdisk lasers of quantum dots were fabricated with both unintentional defects from fabrication, and intentional defects engineered with controlled size. The effects of the defects on the spectral and directional emissive properties were studied.

We have fabricated microdisk lasers of colloidal quantum dots in circular and elliptical forms with different aspect ratios. By characterizing the laser emission spectrum under optical pumping and through mode simulation calculations, we demonstrate that the elliptical resonators can display two sets of whispering-gallery modes that interact to varying degrees depending on the aspect ratio. This causes significant mode splitting in the emission spectra when the mode interaction is at maximum. We also performed angular-dependent laser emission measurements for characterizing the emission pattern of the microlasers. We found that the emission pattern becomes less isotropic and more directional as the boundary deviates further from circular symmetry. In addition, we demonstrate that the emission directional properties of these microlasers can be further tailored by coupling pairs of elliptical microcavities together in different manners, where the long or short elliptical axis interacts most strongly.

The stable multicast flow aggregation (MFA) problem in internet protocol (IP) over optical network under the dynamical scenario is studied. Given an optical network topology, there is a set of head ends and access routers attached to the optical network, in which each head end can provide a set of programs (IP multicasting flows) and each access router requests a set of programs, we find a set of stable light-trees to accommodate the optimally aggregated multicast IP flows if the requests of access routers changed dynamically. We introduce a program correlation matrix to describe the preference of end users' requests. As the original MFA problem is NP-complete, a heuristic approach, named most correlated program first (MCPF), is presented and compared with the extended least tree first (ELTF) algorithm which is topology-aware. Simulation results show that MCPF can achieve better performance than ELTF in terms of stability with negligible increment of network resource usage.

Optical networks employing wavelength- division multiplexing (WDM) are prone to failures. In case of a failure, the time to recovery is an important metric, since the amount of lost information and the performance of carried application strongly depends on the time of service interruption. Moreover, as the current trend in network development is moving toward a unified solution providing support for voice, data and various multimedia services, different application and users may tolerate different time of service interruption. Therefore, it is imperative to provide recovery-time guaranteed connections in WDM optical networks. In this paper, we propose a new shared-segment protection algorithm, called AGBSP-QoP, to provision connection requests according to their differentiated recovery-time requirements. Given a working path, AGBSP-QoP first computes all possible recovery-time guaranteed working-backup segment pairs, and then dynamically selects a least-cost eligible subset based on a dexterously constructed auxiliary graph. We conduct simulations under single class of service and multiple classes of service, and compare AGBSP-QoP with other protection algorithms. The results show that AGBSP-QoP yields the best performance and can properly provision connection requests according to their differentiated recovery-time requirements.

In the IEEE 802.17 standard, bridging is suggested to connect multiple resilient packet rings (RPRs). However, the inherent bridging technology may not be a feasible solution because too many resources and too much overhead would be occupied or needed to transmit packets across multiple RPR networks. Therefore, extended definitions of a standard RPR frame, transmission technology, and multi-ring based auto- topology discovery are described and analyzed in this paper. These extensions and new mechanisms particularly support interconnected resilient packet rings (IRPRs), and although different, they are compatible with the standard RPR. We show that the proposed solution can overcome the shortcomings of connecting multiple RPRs by a new technology, and thus facilitate the RPR technology to match WAN applications.

This paper studies the routing problems in Internet protocol/wavelength-division-multiplexing (IP/WDM) networks based on the overlay routing algorithm (ORA) and the integrated routing algorithm (IRA), respectively. Although IRA usually outperforms ORA in terms of blocking performance, IRA exhibits disadvantages in control information exchange, network privacy issue, and wavelength port efficiency. In this paper, a new mechanism called the short lightpath establishment approach (SLEA) is proposed for ORA in order to tackle the problems in IRA and achieve similar (or even better) network performance at the same time. The main idea of SLEA is to ensure that each new lightpath created by ORA is restricted by an optical hop constraint when a subwavelength-granularity connection is routed in the optical layer. It follows that SLEA essentially avoids per-connection-based greedy treatment and improves network wide resource utilization by eliminating inefficient long optical bypasses. To implement SLEA in ORA, the Dijsktra's algorithm has been modified based on an extended layered graph model. SLEA does not introduce any additional signaling and computational complexity. The analysis and simulation in this paper show that there exists an optimal optical hop constraint for each particular network configuration such that SLEA-based ORA (SLEA-ORA) can efficiently utilize the network resource of concern. As a result, with the optimal optical hop constraint, SLEA-ORA could outperform ORA and IRA in terms of the bandwidth-blocking ratio (BBR) and the average number of IP hops of label-switched paths (LSPs).

This paper investigates the untraditional approach of contention resolution in Wavelength Division Multiplexing (WDM) Optical Packet Switching (OPS). The most striking characteristics of the developed switch architecture are: (1) Contention resolution is achieved by a combined sharing of Fiber Delay-Lines (FDLs) and Tunable Optical Wavelength Converters (TOWCs); (2) FDLs are arranged in non-degenerate form, i.e., non-uniform distribution of the delay lines; (3) TOWCs just can perform wavelength conversion in partial continuous wavelength channels, i.e., sparse wavelength conversion. The concrete configurations of FDLs and TOWCs are described and analyzed under non-bursty and bursty traffic scenarios. Simulation results demonstrate that for a prefixed packet loss probability constraint, e.g., 10−6, the developed architecture provides a different point of view in OPS design. That is, combined sharing of FDLs and TOWCs can, effectively, obtain a good tradeoff between the switch size and the cost, and TOWCs which are achieved in sparse form can also decrease the implementing complexity.

The rate equations and power evolution equations of erbium/ytterbium codoped phosphate fiber amplifiers are solved numerically and its results are compared with measured data in literature. Based on the numerical analysis, optimal erbium and ytterbium codoping concentrations are supposed, and with a pump power of 224 mW and a fiber length of 3.6 cm, the internal gain of 31.0 dB and gain per unit length of 8.6 dB/cm may be achieved in the fiber with the optimal codoping concentrations.

This letter provides a scalable slotted ring network architecture with nodes using one fixed transmitter, one tunable transmitter and multiple fixed receivers. Furthermore, the novel access protocol with efficient slot reuse is proposed. Theoretical analysis and simulation results show that protocol can achieve high node throughput and low queuing delay.

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.

This paper focuses on dynamic integrated routing in multifiber Internet protocol/wavelength-division multiplexing (IP/WDM) networks, which can be implemented through either one-step routing (OSR) or two-step routing (TSR) approach. Based on an extended layered-graph, two resource assignment strategies, termed channel-level balance (CLB) and link-level balance (LLB), are proposed to balance the traffic in the network at different levels. To further improve the performance, a parameter K is introduced to make a dynamic tradeoff between the logical-layer links and the optical-layer links. Simulation studies are carried out for various topologies. The results show that LLB is better than CLB in most cases, and LLB combined with OSR has the optimal performance. Also, we find that the routing approach and the resource assignment strategy individually play different roles with different values of r/sub l/ that is introduced to indicate the resource richness of the network. As a multifiber network is functionally equivalent to a single-fiber network with limited wavelength conversion, we investigate the effects of wavelength conversion by studying the multifiber IP/WDM networks. The analysis shows that, when the granularity of each connection request is much smaller than the wavelength granularity, wavelength conversion may increase the request blocking probability in the network.

In this paper, we study the problem of multi-layer integrated survivability (MLIS) for efficiently provisioning reliable traffic connections of arbitrary bandwidth granularities in the integrated optical Internet. We decompose the MLIS problem into three sub-problems: survivable strategies design (SSD), spare capacity dimensioning (SCD), and dynamic survivable routing (DSR). First, a review of network survivability in multi-layer IP/WDM networks is provided. Then, multi-layer survivability strategies are proposed and it is observed how these strategies could be applied to the integrated optical Internet architecture. We also present an enhanced integrated shared pool (ISP) method for solving the static MLIS problem (i.e., the SCD sub-problem) and the priority-based integer programming formulations are also given. Moreover, we design a novel scheme called the differentiated integrated survivability algorithm (DISA) to solve the dynamic MLIS problem (i.e., the DSR sub-problem), which employs flexible survivable routing strategies according to the priority of the traffic resilience request. Performance simulation results of DISA show that our adaptive survival schemes perform much better in terms of traffic blocking ratio, spare resource requirement, and average traffic recovery ratio compared with other solutions in the optical Internet.

A new online multi-layer integrated routing (MLIR) scheme that combines IP (electrical) layer routing with WDM (optical) layer routing is investigated. It is a highly efficient and cost-effective routing scheme viable for the next generation integrated optical Internet. A new simplified weighted graph model for the integrated optical Internet consisted of optical routers with multi-granularity optical-electrical hybrid switching capability is firstly proposed. Then, based on the proposed graph model, we develop an online integrated routing scheme called differentiated weighted fair algorithm (DWFA) employing adaptive admission control (routing) strategies with the motivation of service/bandwidth differentiation, which can jointly solve multi-layer routing problem by simply applying the minimal weighted path computation algorithm. The major objective of DWFA is fourfold: 1) Quality of service (QoS) routing for traffic requests with various priorities; 2) blocking fairness for traffic requests with various bandwidth granularities; 3) adaptive routing according to the policy parameters from service provider; 4) lower computational complexity. Simulation results show that DWFA performs better than traditional overlay routing schemes such as optical-first-routing (OFR) and electrical-first-routing (EFR), in terms of traffic blocking ratio, traffic blocking fairness, average traffic logical hop counts, and global network resource utilization. It has been proved that the DWFA is a simple, comprehensive, and practical scheme of integrated routing in optical Internet for service providers.

Based on the combined model of erbium-doped waveguide amplifier with high erbium ion concentration, the rate equation and evolution equation is solved numerically. The waveguide parameters such as doping concentration, waveguide length are optimized in this paper. With pumping power of 150 mW , the optimal erbium doping concentration and waveguide length is 6×10 26 m −3 , 15 cm or so, respectively. The amplifier with these optimal parameters may reach gain more than 35 dB .

Based on the homogenous model and inhomogeneous model of concentration quenching of erbium-doped fiber amplifier with high doping concentration, the rate equation and power evolution equation of erbium-doped phosphate fiber are solved numerically and analyzed. The dependence of the calculated gain and noise figure on pump power is compared with experimental data, and the results indicate that the combined model of the two models is in good agreement with experimental data. The relative number of clusters in erbium-doped phosphate fibers is estimated from the numerical analysis, and the optimal doping concentration and length of erbium-doped phosphate fibers are proposed in this paper. By numerical analysis, the results show that with 200-mW/980-nm pump power, an erbium-doped phosphate fiber amplifier with a doping concentration of 4.0/spl times/10/sup 26/ ion/m/sup 3/ and length of 10 cm may reach 27.0-dB gain.

In this paper we design a 120 nm bandwidth erbium-doped fiber amplifier using a seed light injection method for the first time. It is shown that when the wavelength of the seed light varies from 1520 to 1570 nm , the gain at 1610 nm reaches maximum near 1553 nm and increases as the seed light power. Based on the method, a novel split-band EDFA configuration is designed. The split-band architecture employs a 1550/1610 nm waveband multiplexer/demultiplexer and two independent sub-bands which pass in parallel through separate branches of the optical amplifier. The signals at independent sub-bands are combined and flattened before output, resulting in a broadband gain-flattened optical amplifier with 120 nm bandwidth.

Network survivability is a crucial requirement in WDM mesh networks. In this paper, we systematically consider the problem of dynamic survivability with dynamic single link failure in WDM networks under dynamic traffic demands. Specifically, we investigate various protection schemes, such as dedicated path protection (DPP), shared path protection (SPP), dedicated link protection (DLP), shared link protection (SLP), and two restoration schemes, path restoration (PR) and link restoration (LR). Moreover, two new shared protection methods are proposed, i.e., SRLG-based shared link protection (SRLG-SLP) and SRLG-based shared path protection (SRLG-SPP). The SRLG (shared risk link group) constraint defines the availability of protection resources to a working path, which requires that any two working paths sharing the same risk of failure (or in the same SRLG) cannot share the same protection resources. Furthermore, in our study, we consider a more practical dynamic single-link failure model, in which the link-failure-interarrival time and link-failure-holding time are considered as two independent parameters. Based on this link-failure model, extensive simulations are done to analyze and compare the dynamic survivable performance of various protection and restoration schemes. Resource utilization, protection efficiency, restoration efficiency, and service disruption ratio are employed as survivable performance metrics versus traffic load, link-failure frequency, and link-failure reparation time to evaluate the survivable performance. Many meaningful results are given. In addition, we show that the developed SRLG-SLP and SRLG-SPP protection schemes perform very well in terms of protection efficiency and service disruption ratio, while sacrificing some performance in terms of resource utilization.

This study reports a facile on-chip fabrication of CdSe/Cd1−xZnxSe1−ySy quantum dot microdisk lasers and their large-area arrays via a pattern-assisted layer-by-layer assembly process. This approach combines the versatility of colloidal semiconducting nanoparticles (bright emission, solubility, and high stability) with the spatial precision of optical lithography to create robust large-area optical lasing arrays (up to a few thousand disks). Specifically, microdisk lasers with high quality factors (within 1000–2000) are fabricated with predefined size and shape (as controlled by master templates) with high consistency and throughput, essentially providing a new approach to fabricate difficult-to-control on-chip optical cavities in a low-cost and effective manner. Notably, the number of longitudinal cavity modes in the microdisk laser can be precisely controlled by varying the microdisks' diameter, allowing for either near-single mode or multimode operation while preserving high quality factors. Furthermore, the cross-linking of quantum dots imparts high chemical resistance and mechanical robustness that helps retain the structural integrity under harsh processing conditions (such as sonication or direct exposure to various solvents). As such, these quantum dot microdisk laser arrays are promising candidates for advancing the development of large-area, low-cost on-chip photonic structures with controlled lasing modes.

Based on traffic prediction, a new reservation method is proposed to reduce delay and void filling ratio at edge node of optical burst switching networks. Simulation studies show that our method achieves an important improvement and has a dynamic optimum weight value in a certain offset time.

To achieve higher resource utilization in IP/WDM networks, this paper develops an approach called hop-constraint lightpath establishment approach (HCLEA) to improve existing routing algorithms. HCLEA prevents the routing algorithm from creating long lightpaths with low efficiency. Simulation results show that HCLEA can achieve a significant improvement in terms of resource utilization and bandwidth blocking ratio.

The most important feature of the Raman-gain spectrum is that the peak-gain wavelength only depends on the pump wavelength (fixed shift about 100 nm). Using this feature, a new optimal algorithm for multipump sources of a distributed fiber Raman amplifier is designed. The numerical analysis results show that the optimal algorithm is simple and effective.

In WDM optical networks, a low speed traffic is often multiplexed or switched into a high speed lightpaths. In common measures, a lightpath established in traffic grooming does not consider transmission impairment. It transports traffic optically as long as possible. But optical medium is not ideal, transmission impairment like ASE noise, which degrades the signal to noise ratio, exists. To maintain an acceptable SNR level at the receiver side, the number of optical amplifiers in a lightpath should not exceed a Maximum value (M). A segment between two optical amplifiers referred as a span. In this paper, we adds span constraints to the traffic grooming problem, and present an heuristic algorithm to bring up a series of lightpaths explicitly to accommodate such traffic. From the numerical result, it could be found that it guarantees each traffic to be successfully routed. It also achieves good performance of wavelength efficiency and lightpath efficiency.

We propose a novel distributed reservation scheme in which signaling packets collect OXCs configuration status of each available wavelength. It will minimize the number of switch fabrics reconfigured and significantly shorten the connection setup time.

The proposed scheme for multi-granular grooming presents a distinctive approach of dividing granularities into special tunnels for effective treatment. We first introduce the new optical switching fabric based on lambda-group model, as well as algorithms under dynamic environment. Results and figures from experiments show that the particular channel partition not only is helpful to port reduction significantly, but also improves the SNR of signal and blocking performance for dynamic connection requests.

The performance analysis of distributed connection management for WDM optical networks with different nodal degrees is proposed in this study. In our previous study, we proposed a distributed wavelength reservation scheme with switch fabrics status. We consider the reconfiguration information of switch fabrics in the signaling protocol, which designated as the signaling with switch fabric status (SWFS). Distributed reservation algorithms will reserve the wavelength with minimum of reconfiguration times of OXCs along the route to shorten the connection establishment time. In this paper, we analysis the reservation schemes with or without SWFS for FAXC or FBXC modes, especially the performance with different nodal degrees. The simulation results indicate that schemes with SWFS have the shorter setup time, lower switching ratio than those without SWFS. The schemes for FBXC mode have the better blocking performance than those for FAXC mode. The switching ratio, the blocking probability and connection setup time decrease with the increase of nodal degrees for S-RM. The increase of the nodal degree from 2 to 3 and from 6 to 7 leads to higher nodal degree gains.

A new scheme to mitigate the connection setup time and minimize the reconfiguration times of optical cross- connects (OXCs) for WDM optical networks is proposed in tins study. In tins new scheme, we consider the reconfiguration information of switch fabrics in the signaling protocol, winch designated as the signaling with switch fabric status (SWFS). Distributed reservation algorithms will reserve the wavelength with minimum of reconfiguration times of OXCs along the route. Simulation results indicate that our proposed schemes with switch fabrics status have the shorter setup time, lower switching ratio as well as better blocking performance than those of the classic schemes. Especially, the reservation schemes all have constant switching ratio under the environment on different switching delay of OXCs or different requests. Moreover, the proposed schemes with SWFS significantly reduce the number of switch fabrics that need to be reconfigured.

The impact of IP over optical two-layer multicasting on the performance of channel zapping is discussed through two simple experiments and evaluated by an large scale concurrent video delivery testing in the 3TNet testbed in Yangtze River Delta, China. The results of 1040 concurrent users testing are reported.

A new splitter-and-delivery (SAD) switch having multicasting capability is proposed. It is best implemented in a single silicon board using planar silica waveguide technology. Less than -40-dB crosstalk is achievable by an auxiliary action of the optical gate. Three optical cross-connect architectures employing the SAD switch are proposed. They are strictly nonblocking and have multicasting capability. Furthermore, they have wavelength or fiber modular structures and are expandable when the number of the fibers and the wavelengths increase a few or by a few times. The expanding method and other important issues are discussed in detail.

A new scheme to mitigate the connection setup time overheads in distributed wavelength reservation schemes for WDM multi-fiber optical networks is proposed in this study. In this scheme, we consider the reconfiguration delay of switch fabric in distributed signaling protocols, which designated as signaling with switch fabric status (SWFS). Protocol realization selects and reserves the available wavelength that has the least switch fabric reconfiguration times along the path to shorten the connection establishment time. In this paper, we proposed four wavelength reservation schemes with SWFS for multi-fiber optical networks, which are S-FW-FF, S-FW-RF, S-RW-FF, and S-RW-RF. Simulation results indicate that schemes with SWFS have the shorter setup time, lower switching ratio as well as better blocking performance than those of without SWFS. Especially, the proposed schemes significantly reduce numbers of switch fabric that need to be reconfigured.

In IP over WDM networks, when a failure (such as a fiber cut) occurs, the service restoration can be implemented by dynamic routing in IP layer. But it needs the logical 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 (light paths) on a physical network topology in a way that the logical topology remains connected in the event of single physical link failure is called survivable routing. In this paper, we address the survivable routing problem by proposing a new ILP algorithm. The necessary and sufficient conditions for survivable routing are simplified, which greatly reduces the number of survivable constraints for sparse-connected logical topologies. 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 ILP variables. Finally, numerical results are given and discussed to show that most survivable routing solutions can be found by our algorithm. Further more, comparing with other similar methods, our algorithm can find out a survivable solution in much smaller time, and it works especially well with sparse-connected logical topologies. The factors that influence the probability to find out a survivable solution are also discussed in this paper.

Optical Burst Switching (OBS) has been developed as an efficient switching technique to exploit the capacity provided by Dense Wavelength Division Multiplexing (DWDM) transmission technology for the next generation optical Internet. Segmentation is proposed in literatures to resolve contention, a major concern in optical burst switched networks. As far as segmentation is concerned, nearly all the methods introduced in the literatures adopt tail-dropping policy. In this paper, we will demonstrate, however, that tail-dropping policy may not be a feasible solution to resolve contention. Based upon this, a modified head-dropping solution is proposed. In this method, when the overlap part is no more than the entire contending burst arriving late, the head part of contending burst will be discarded, otherwise the entire contending burst will be dropped. In order to alleviate disorder resulted from head dropping and support Differentiated Services well, we also present a priority-based proportional mixed segment assembly technique to encapsulate burst at edge node. A burst consists of several segments, each of which is a group of same priority packets and has it's own assembly information. We suggest that the priority-based proportional mixed segment assembly be used integrated with modified head-dropping contention resolution policy in OBS networks. The main objective of our segment scheme is to improve the utilization of resource, decrease the packet loss probability, and afford a better Differentiated Services support as well. Experiment results prove that our integrated segment scheme performs well on decreasing packet loss probability and Differentiated Services.

This paper investigates the traffic properties before and after assembly in edge node of Ethernet over optical burst switching (OBS) network for the first time. The features of the edge access system are that (i) Forty Ethernet sources aggregate into optical burst edge node. Moreover they all generate self-similar traffic and have the same parameters. (ii) The packet size of sources follows Pareto distribution with the range from 64 to 1518 bytes. (iii) Packets are assembled into bursts according to four classes and fifteen output ports. Burst and interarrival time distributions are simulated under time-based and length-based assemble schemes. Self-similar traffic Hurst parameter is compared through R/S and V/T plot. Finally three self-similar traffic generating methods are given. Simulation results demonstrate that, multi-source traffic increases self-similar degree, however after assembly, time-assembly scheme can decrease self-similar degree, and aggregated burst size is close to Gaussian distribution. Length-assembly method has no effect on the self-similarity of input traffic. RMD is fit for study of burst network with large self-similarity.

This paper focuses on burst assembly at edge node in optical burst switching networks, which can be implemented to provide the delay QoS guarantee for the whole network. Based on traffic prediction and delay fairness of different classes, a Prediction and delay QoS Burst Assembly (PQBA) mechanism is proposed to reduce the assembly delay and improve the delay fairness especially for high priority service at edge node. We compare the delay, burst size, burst utilization and length error rate of all service classes under different offered load. Simulation studies are carried out for PQBA and the results show that high priority service with relative small burst size achieves a low assembly delay and high burst utilization. Consequently, PQBA realizes the QoS-based delay fairness and service class differentiation at edge node.

A multi-wavelength optical label switching test-bed is introduced. The optical label is constructed by a series of optical pulses with different wavelengths that are in the same WDM optical channel. High speed optical switches and DSP chips are used to process the optical label signal. The four-node programmable optical label switching network is demonstrated by transmitting PC capture signal and multimedia video flow with standard Gigabit Ethernet frame. Furthermore, an optical packet assembly and segmentation method is proposed for Gigabit Ethernet Optical Label Switching networks. Two timers are used to realize the exact timing on microsecond magnitude between optical label and programmable optical Ethernet packet. The experimental system executes the real time process and the Gigabit Ethernet data packets with optical label are switching and transmitting successfully. The optical packet programmable method enhances bandwidth utilization and throughput, increases the intelligence, flexibility and multi-service bearing ability of the Optical Label Switching network.

A kind of optical coarse packet switching based on optical label routing is intrduced. In the switching, the swapping granularity is coarse compared to common optical packet switching, and the header of optical packet is labeled by multi-wavelengths. Some realization techniques on core switching node and edge node with terminator are studied. A principle experiment system is established to perform the optical coarse packet transmitting, switching, and receiving, and verify the feasibility of such optical coarse packet switching.

In this paper, the research interest focuses on the influence of buffer configuration methods on the performance of a shared WDM optical buffer. In order to resolve FDL contention, which often occurs in a shared WDM optical buffer, two improved buffer configuration methods, i.e., duplicated degenerate mode (DDM) and increased degenerate mode (IDM) are proposed. The performances of the proposed buffer configuration methods are evaluated by simulation experiments.

In this paper, a new scheme to mitigate the connection setup time overheads in distributed control schemes for wavelength-routed optical networks is proposed. In this scheme, we consider the reconfiguration delay of switch fabrics in the distributed signaling protocols, which designated as the signaling with switch fabric status (SWFS). Based on the reconfiguration information being carried by signaling messages along with wavelength availability information, distributed wavelength assignment algorithm at the destination node will select a wavelength with the minimal switch reconfiguration delay along the lightpath to shorten average connection setup time. Simulation results indicate that the first-fit algorithm with switch status (S-FF) and random algorithm with switch status (S-RM) have the shorter setup time, lower switch ratio as well as better blocking performance than those of classic schemes. Especially, the proposed scheme significantly reduces the number of switch fabrics that need to be reconfigured. Moreover, we investigate the effect of number of add/drop ports of optical cross-connects (OXCs) on the blocking performance of the scheme. We find that when the number of add/drop ports of OXCs is larger than a base boundary, the network may achieve almost the best blocking performance of the distributed wavelength provisioning.

In this paper, an inner wavelength method (IWM) is proposed to enlarge buffering capacity of shared FDL-buffers. In addition, an optical packet switch called Extended shared buffer type optical packet switch (Extended SB-OPS) is proposed to realize the inner wavelength method. In order to further improve performance of Extended SB-OPS, a greedy algorithm based on inner wavelength method (GA-IWM) is introduced. The performance of Extended SB-OPS is evaluated by simulation experiments.

In the paper, a new optical packet switch is proposed, which uses shared WDM buffers (fiber delay-lines) and shared tunable wavelength converters (TWCs) as contention resolution. In each fiber delay-lines, many wavelengths can be used to buffer packets at the same time. The shared TWCs have two kinds of functions, either as translators for free wavelengths in destination output fibers, or as translators for free wavelengths in the feedback FDLs. Based on this architecture, a lower packet loss rate can be achieved without the need of deploying a large number of FDLs and TWCs. The performance of the new architecture has been extensively studied by means of simulation experiments.

This paper focuses on the problem of buffering performance optimization for optical packet switch with shared WDM (Wavelength Division Multiplexing) optical buffers. For this purpose, several packet scheduling algorithms are proposed to make full use of buffering resources. Influences of these algorithms on optical packet switch are evaluated by simulation experiments. Simulation results show that under different traffic load, different packet scheduling algorithms should be adopted. In addition, the performance of optical buffers also depends on the granularity of FDL.

Both protection and restoration are fundamental consideration in designing robust optical networks, especially in challenging GMPLS/ASON architecture. Fast Rerouting technology as one important method of MPLS-Traffic Engineering is an efficient and powerful technology for protecting MPLS-TE LSPs from link and node failures. By supporting locally reparation of the affected LSPs at the point of failure, link and node protection are achieved quickly. The goal of real-time IP applications over native IP unicast/multicast networks or LDP based MPLS networks is to limit the IP packet loss duration in the network to 10s of milliseconds in the event of link/node failures. RSVP signaled LSP is used with explicitly routed path as the re-direct tunnel, while the protected traffic can be either MPLS traffic engineered LSPs, LDP based LSPs, IP unicast, IP multicast traffic or the mix of them. This mechanism can be applied to both point-to-point links and multi-access links in the cases of the link protection and node protection. Besides the above resilience research on IP/MPLS single layer, tests or experiments on multilayer mechanism, i.e. optical and IP/MPLS network layer composing of multi-vendor routers and multi-domain, are carried out by a number of famous organizations and companies where optical dedicated/shared mesh protection/restoration and MPLS fast rerouting survivable techniques are combined to guard against both dual link failures and combined link and IP/MPLS hardware and software router failures. Those techniques used in next-generation backbone network design result in that not only familiar failures such as fiber cuts or amplifier damage but also system failures such as router failures or multiple concurrent failures can be recovered fast and effectively at corresponding layer. In this paper, on the basis of analysis of IETF's internet drafts about fast rerouting algorithm and standards in MPLS-TE and GMPLS, new fast rerouting algorithm and corresponding simulation results are proposed step by step. At the same time, resilient performance in a GMPLS/ASON design especially under mesh optical protection is studied carefully while a few coming function requirements in OXC and router equipments obtained from the above analysis are discussed to some extent. Figures and tables are presented for explaining the enhanced fast rerouting technology reducing confusion of packets and achieving falling delay time of rerouting. Finally, some issues for further work are to identify the importance where to place appropriate resilient mechanism in the next network design.

This paper considers the dynamic routing issues in WDM grooming networks. Given network resources, a major objective of a routing algorithm is to minimize the blocking probability of connection requests. Wavelengths and transceivers are usually limited resources in a network. The way to use these resources directly determines the network performance. So the challenge is how to use wavelength resources efficiently while keeping higher transceiver-utilization efficiency. To solve this problem, we develop an approach called Hop Constrain Lightpath Establishment Approach (HCLEA). The main idea of HCLEA is to guide the routing algorithms not to create inefficient long lightpaths. Simulation results show that HCLEA does improve the network performance in terms of transceiver-utilization efficiency, wavelength-utilization utilization, and bandwidth blocking ratio.

This paper proposes a collision-free access protocol based on scalable slotted ring network architecture. Multiple QoS classes are supported directly in optical layer. The Qos scheme adopts the fixed home slots strategies to satisfy the requirements of services. Furthermore, efficient slot reuse is proposed. Simulation results show that the protocol can achieve good performance to guarantee the quality of traffic.

This paper presents a multicasting extension to OIF User Network Interface (UNI) standard, which allows dynamically setup/teardown/graft/prune a transport network multicasting tree. Transport network multicasting tree means a point-to-multipoint connection that originates from an ingress Transport Network Element (TNE) port and end at multiple egress TNE ports across the transport network for transporting user services. A global multicasting tree ID is defined to identify the transport network multicasting tree. Without addition of any new abstract messages, we just add some new attributes to existing UNI abstract messages to implement the signaling actions needed to support optical multicasting. Experimental results show the performance of our proposal under different strategy.

In this paper, a new type of p-cycles, multi-granularity flow p-cycles (MFP), is presented. A two-step approach is developed for the design of MFP with span failure recovery. Our simulation results show that MFP are more capacity-efficient than conventional span-protecting p-cycles (SP) and flow p-cycles (FP). The impacts of network topology on performance of SP, FP and MFP are evaluated. In this paper, we also propose a new p-cycle pre-selection strategy. Results show that our strategy is more efficient than two existing pre-selection strategy in p-cycle networks.