Optical Packet Switching Networks Research Articles

Parallel-to-Cascading Optical Code Label Processing in Optical Packet Switching Networks

Parallel-to-cascading optical code (OC) label processing based on fiber Bragg grating is proposed and experimentally demonstrated. With this technique, the length of the multibit OC label is the same as that of the one-bit OC label; only one encoder and one decoder are needed for the multibit OC label's generation and recognition; the relatively low-speed recognition patterns also reduce the complexity of generating the control signal. The experimental results show that both the ratio of autocorrelation peak to cross-correlation peak (ACP/CCP) and the ratio of ACP to maximum autocorrelation wing are higher than 8 dB in the multibit label's decoded signal, so the parallel-to-cascading OC label processing is practical for optical packet switching networks.

Multibit Information Optical Code Label Processing in Optical Packet Switching Networks

Multibit optical code (OC) label and its en/decoder based on fiber Bragg grating is proposed and experimentally demonstrated. The multisampling technique is introduced into the label's encoder, then the maximum number of bits that one label can carry is significantly increased. The label's multibit information can be recognized by a single cascaded decoder. The experimental results show that a higher than 10-dB ratio of autocorrelation peak to cross-correlation peak and a higher than 9-dB ratio of autocorrelation peak to maximum autocorrelation wing can be realized simultaneously for label's recognition, so the multibit OC label is practical for optical packet switching networks.

Metropolitan optical packet bus-based networks: Packet bursting and emulation of TDM services

The volume of network traffic, notably of data traffic, grows continuously and tremendously during recent years with the appearance of new value-added services such as video on demand, interactive video conferencing, peer to peer data sharing, etc. Faced with this challenge, traditional circuit-switched networks become inappropriate and costly. On the other side, optical packet-switched networks, which support best data traffic thanks to their high flexibility, capacity, and cost-efficiency, appear the most appropriate candidate. To optimise the transmission efficiency of packets in optical networks, a new technology, Modified Packet Bursting (MPB), has been studied in the framework of a metropolitan optical packet bus-based network. Also, in order not to degrade the quality of classical circuit-switched Time Division Multiplexing (TDM) services, which still stay the major revenues of telecom operators today, Circuit Emulation Service (CES) on packet-switched networks has been investigated by main standard organizations. This paper presents the performance analysis of the above two technologies applied to a metropolitan optical packet bus-based network. It specially demonstrates the improvement of CES performance thanks to MPB features.

A new performability model for queueing and FDL-related burst loss in optical switching nodes

Optical packet and burst switching have been proposed for networks because of the increased demand for capacity to transport traffic generated by various applications at present and in future. In optical packet switching networks the payload and the header of a packet are conveyed in the same channel, while burst switching networks allow the separate transportation of the payload and the header of bursts. In this paper we propose a queueing model for an optical node with a number of wavelengths and a buffer made from Fiber Delay Loops (FDL). We also apply negative customers in the queueing model in order to account for the loss of bursts due to the limitation related to the FDL (i.e. bursts can stay in a FDL buffer only for a limited period of time). Numerical results based on the analytical model are compared to the results obtained by simulation of optical burst switching nodes with the FDL buffer and input traffic using packet traces from the Internet Traffic Archive, which shows the accuracy of the proposed model.

Quality of Service Aware Call Admission Control in Cell Based Multi-Service Photonic Network

The article tackles the problem of quality of service assurance in photonic networks. The idea of multi-servicephotonic network model with the coexistence of optical circuit and packet switching mechanisms and cell communication is used as a basis for service differentiation in the optical domain. Cell loss ratio as a key performance indicator determines the required optical switching mechanism. Service provisioning is performed using call admission control mechanism with real-time cell loss ratio estimation procedure. Service blocking probability calculation utilizes discrete event simulation of service provision and teardown requests applied to core network topology from COST 266 project. Three simulation scenarios are included in the analysis – pure optical packet switching network, and coexistence of optical packet and circuit switching with and without possibility of communication redirection between the switching mechanisms. Simulation scenarios are additionally altered with the cell loss ratio constraint and number of delay lines.

<inline-formula><math display="inline" overflow="scroll"><mrow><mn>1</mn><mo>×</mo><mn>2</mn></mrow></math></inline-formula> switching cell for optical packet-switched networks

We demonstrate a 1×2 optical switch using LiNbO3 modulators for optical packet switching. The switch can be used to construct N×N optical switches for optical packet-switched networks. The optical switch has a fast response time and high on/off switching ratio. The behavior of the switching device is investigated with numerical simulations and experimental measurements.

Blocking probability computation in reversible Markovian bufferless multi-server systems

We study the blocking probability in a Markovian bufferless queuing system with a finite number of servers when the packet arrival process is a Markov-modulated Poisson process (MMPP), a superposition of a finite number N of independent MMPPs. We present an algorithm to compute the blocking probability in the system. The algorithm is exact if some related Quasi-birth-and-death (QBD) processes are reversible. We prove that the complexity of our algorithm scales linearly with N , whereas that of the standard solution does it exponentially. We illustrate the use of our algorithm in a bufferless multi-server system receiving long-range dependent (LRD) input traffic. This problem finds applications in the study of the blocking probability in bufferless optical packet switching (OPS) and optical burst switching (OBS) networks. We emulate LRD traffic with an MMPP, a superposition of N independent ON/OFF sources, which are also MMPPs. Our algorithm is in this case approximative since the reversibility condition is not fulfilled with the proposed MMPP. An extensive numerical analysis suggests that our algorithm can accurately approximate the blocking probability in the original queueing system with LRD input traffic. We provide an insight into the reason why our approximation is accurate.

A novel scheme of two-dimension time-stacked wavelength–time optical code label for optical packet switching network

A novel scheme of time-stacked optical code label based on optical code division multiple (OCDM) technique for optical packet switching network is proposed, in which two-dimensional wavelength–time OCDM code is used as the optical label. Packet loss rate and system characteristic based on the proposed scheme are studied. Results show that less packet loss rate of proposed scheme can be achieved as compared with that of one-dimension time-stacked optical code label system.

Packet Pacing in Small Buffer Optical Packet Switched Networks

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

Optical Code Label Stripping based on SOA-MZI in Optical Packet Switching Networks

As an alternative to label swapping, an all-optical label stripping scheme based on SOA-MZI is proposed. The stripping process is self-controlled without any synchronization process. Simulation results show that high-quality stripping can be achieved, with no more than 0.09 dB of power fluctuation and 0.05 dB of phase fluctuation in stripped and remaining label. A power contrast ratio of 28 dB between the remaining and residual stripped label, and 30-dB signal-to-noise ratio can be reached, respectively. Parameters tolerance analysis shows that the stripping performance deteriorates little when considering the devices' imperfection in practice. The multihop simulation results also show that our scheme is applicable to large-scale optical packet switching networks.

Integrated 1 $\times$ 8 Optical Phased-Array Switch With Low Polarization Sensitivity for Broadband Optical Packet Switching

An InP/InGaAsP integrated 1 times 8 optical phased-array switch is designed, fabricated, and characterized for high-throughput broadband wavelength-division multiplexed (WDM) optical packet switching application. With a single stage of phase shifters utilizing carrier-induced refractive index change, switching to the eight output ports is demonstrated successfully. The polarization-dependent loss is 2.2 dB in the worst case, and the wavelength-dependent loss is less than 2.5 dB across the entire C-band (1520-1580 nm) with the average extinction ratio of 17.7 dB. The measured reconfiguration time is shorter than 6 ns. Low-penalty transmission of a 40-Gb/s non-return-to-zero signal is also demonstrated for the first time. These features make the integrated phased-array switch an attractive candidate to be deployed in the future high-capacity optical packet switching networks.

Even Slot Transmission in Slotted Optical Packet-Switched Networks

The issue of transmitting optical packets (called slots in this paper) smoothly toward an egress switch appears to be overlooked in bandwidth access schemes proposed for optical packet-switched (OPS) networks. Here, we explain the benefits of providing an even (smooth) slot transmission and propose four basic metrics and three hybrid metrics to achieve an even slot transmission from an ingress switch of a multiwavelength/fiber slotted OPS network. The even slot transmission can help improve network performance parameters required for Internet applications. An index parameter is also introduced for each method, and a formulation is provided to gauge how even a transmission is among different combinations of frame periods, wavelengths, and fibers. These formulations can provide us with a new approach to relatively compare different bandwidth access schemes in order to determine which scheme can provide an even transmission of traffic to an OPS network. An example is provided for the comparison of two existing bandwidth access schemes in terms of even transmission of traffic.

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

We developed novel network interfaces, for example 10 Gbit Ethernet to 80 Gbit/s optical-packet (10 GbitE-80 GbitOP) or 80 Gbit/s optical-packet to 10 Gbit Ethernet (80 GbitOP-10 GbitE) converters (collectively called as 10 GbitE/80 GbitOP converters), to connect optical packet switching (OPS) networks with IP technology-based networks. By using newly developed arrayed burst-mode optical packet transmitters/receivers together, the 10 GbitE-80 GbitOP converter at the ingress edge node of the OPS network encapsulates an IP packet into an 80(8lambda×10) Gbit/s dense wavelength division multiplexing (DWDM)-based optical packets and generates an optical label based on a lookup table and the destination addresses of the IP packet. The 80 GbitOP-10 GbitE converter at the egress edge node decapsulates the IP packet from the optical packet and generates a 10 GbitE frame accommodating the IP packet according to a lookup table. By using these network interface devices and OPS system based on multiple optical label processing, we achieved, for the first time, 74-km single-mode fiber transmission, switching, and buffering of 80(8lambda×10) Gbit/s DWDM-based optical packets encapsulating almost 10 Gbit/s IP packets with error-free operation (IP packet loss rate < 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> ).

Guaranteeing packet order in IBWR optical packet switches with parallel iterative schedulers

AbstractThe input‐buffered wavelength‐routed (IBWR) switch is a scalable switch fabric for optical packet switching (OPS) networks. In synchronous operation, when optical packets are of a fixed duration and aligned at switch inputs, the scheduling of this architecture can be characterised by a type of bipartite graph matching problem. This challenges the design of feasible algorithms in terms of implementation complexity and response time. A previous work presented and evaluated the insistent parallel desynchronized block matching (I‐PDBM) algorithm for the IBWR switch. I‐PDBM is a parallel iterative scheduler with a good performance and a simple hardware implementation. However, the algorithm does not maintain the packet sequence. In this paper, we present the I‐PDBM algorithm with packet ordering (OI‐PDBM), which prevents mis‐sequencing and behaves as I‐PDBM in terms of delay, buffer requirements and convergence speed. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Stacked optical code label for multicasting in optical packet switching networks

Stacked optical code (OC) label and its en/decoder based on fiber Bragg gratings (FBG) are proposed and experimentally demonstrated. This kind of label can carry several nodes' address information simultaneously in optical packet switching networks, so it can be employed in optical multicasting and simplify the node's structure a lot. The en/decoder is fabricated with high precision by our FBG techniques, and the experiment results show that the stacked OC label can support optical multicasting very well.

A Novel Packet Switch Node Architecture for Contention Resolution in Synchronous Optical Packet Switched Networks

Packet contention is a key issue in optical packet switch (OPS) networks and finds a viable solution by including optical buffering techniques incorporating fiber delay lines (FDLs) in the switch architecture. The present paper proposes a novel switch architecture for packet contention resolution in synchronous OPS network employing the packet circulation in FDLs in a synchronized manner. A mathematical model for the proposed switch architecture is developed employing packet queuing control to estimate the blocking probability for the incoming traffic. The switch performance is analyzed with a suitable contention resolution algorithm through the computer simulation. The simulation results substantiate the proposed model for the switch architecture.

GMPLS-based packet contention resolution in connection-oriented OPS networks

Approaches for contention resolution among packets in the optical domain have been traditionally devised for distributed operation locally within individual nodes, exploiting both the time and wavelength dimensions. In this work, we focus on packet contention prevention in an optical packet-switched network, tackling the problem from the perspective of a network-wide end-to-end label-switched path (LSP) admission control and LSP-to-wavelength assignment. We present two contention-preventing wavelength assignment schemes, called minimum interference (MI) schemes, that can be implemented within a network control plane based on a generalized multiprotocol label switching (GMPLS) protocol suite. MI schemes envision that LSP-to-wavelength assignment is accomplished by a novel ranking policy utilized for the tie breaking of the GMPLS label set (i.e., the available wavelength set). Specifically, the novel GMPLS object named the suggested vector (SV) is populated during forward propagation of the path message, collecting, for each wavelength, the amount of bandwidth not interfering with already-established LSPs. During the backward propagation of the Resv message, the actual LSP-to-wavelength allocation is performed based on the preference level stored in the SV object. Numerical results show that MI schemes are effective in decreasing end-to-end packet loss and wavelength conversion probabilities, compared with the no-preference scheme that does not exploit such optimization.

Continuously Tunable Optical Buffering at 40 Gb/s for Optical Packet Switching Networks

All-pass, wavelength-selective, slowlight optical buffers using cascaded micro-ring resonator filters are theoretically and experimentally studied in the context of optical packet switching router architectures. Two optical buffers fabricated in high-index contrast silica technology are compared: an 8-ring buffer with narrow resonances for wavelength selective delay and a 32-ring buffer for distortion-free delay at 10 and 40 Gb/s. Accurate measurements and configurations of the transmission of the buffers allow for precise simulations that accurately predict pattern dependent distortions, signal integrity and performance extrapolation to higher data rates. Continuously tunable delays are demonstrated up to 8 bits with minimal distortion.

Performance analyses of serial-mode multicasting scheme in optical packet switched networks

The serial-mode multicasting scheme (SM), which can achieve duplication, buffering, and serial export of optical multicast packets in Optical Packet Switched (OPS) networks, is experimentally studied in this paper. Based on the experimental results, several limitations of this scheme, such as the multicast latency and signal impairment, are discussed. In addition, its performance in OPS networks is investigated by computer simulations. From the simulation results, a conclusion can be drawn that compared with the parallel-mode multicasting scheme (PM) producing multiple simultaneous copies of the optical packets by an optical power splitter or other devices, the SM scheme can increase the multicast success ratio and reduce the multicast retransmission times at the costs of some signal impairments and some extra transmission latency.

Improving throughput of long-hop TCP connections in IP over OPS networks

Optical Packet Switching (OPS) can provide the ever-increasing bandwidth required for Internet traffic and new applications for future networks. However, optical packet loss is the major problem for an OPS network. Moreover, by increasing the number of hops between a pair of ingress–egress switches in an OPS network, optical Packet Loss Rate (PLR) between this pair is increased. Therefore, due to a higher PLR for long-hop TCP connections, the throughput of these connections may be much lower than the short-hop TCP connections. To overcome this problem, it is proposed in this paper to use the retransmission idea in the optical domain not only to increase TCP throughput but also to improve the throughput of multi-hop TCP connections, and also to have a loss-free OPS network. Under retransmission in the optical domain, a copy of the transmitted traffic is kept in the electronic buffers of ingress switches and retransmitted in the optical domain whenever required. Note that the TCP layer has its own retransmission at the client packet level as well. By retransmission of lost packets in the optical domain, TCP would be unaware of the lost client packets, and therefore, TCP would not reduce its sending rate. In this paper, TCP throughput is studied in a bufferless slotted OPS network and the effectiveness of the proposed mechanism is evaluated.