Optical Packet Switching Node Research Articles

The designs of a scalable optical packet switching architecture

This paper proposes a new switching architecture to be used in all optical packet switching networks. The proposed switch is derived from an original 2 × ?2 two‐stage multi‐buffer switched delay line based optical switching node, known as an M‐Quadro node. By incorporating bypass lines into the M‐Quadro architecture and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. Furthermore, we show that such architecture is scalable for a generic multiple stages optical packet switch with a larger number of input/output ports.

Optimization of a Switching Node for Optical Multistage Interconnection Networks

In this letter, we demonstrate a 2 times 2 switching node optimized for optical multistage interconnection networks. The optical packet-switched node is improved by making use of comparators with dual-threshold action to regenerate the routing header signal. The switching node is shown to correctly route packets with the presence of glitches in the header information. We employ a hybrid integrated semiconductor optical amplifier in the switching node that reduces packet guard times enabling a 67% increase in the number of stages for large-scale multistage networks.

Placements of Shared Wavelength Converter Groups Inside a Cost-Effective Permuted Clos Network

The Clos network is used for optical cross-connect and optical packet switch node, and has a large number of cross-points if the number of wavelengths per fiber is more than that of fibers per node. In this letter, we propose a cost-effective permuted Clos network to reduce the number of crosspoints. We further investigate the placement of fixed wavelength converter groups (WCGs) shared inside the permuted Clos network. On the contrary, a normal Clos network has to be equipped with expensive tunable WCGs. The simulation result implies that equipment of about 50% WCGs achieves similar performance as the full wavelength interchanging node does.

Gain uniformity optimization of SOA-based optical packet switching nodes for performance and scalability improvements

A design methodology is proposed that can potentially provide effective bandwidth and scalability improvements to optical packet switching environments utilizing semiconductor optical amplifiers as broadcast-and-select switching elements. The design achieves added uniformity in the nodal gain-loss spectrum. The methodology is tested and verified using a commercial device with measurements performed on the gain, noise figure, optical signal-to-noise ratio, and power penalty.

Service category-to-wavelength selection technique for QoS support in connection-oriented optical packet switching

This paper considers an optical packet-switched node subject to asynchronous, variable-length packets and connection-oriented operation. We firstly address the problem of setting up the optical virtual connections and properly configuring the forwarding table at the node. We do not deal with routing aspects, but with the efficient mapping of the virtual connections to the wavelengths of the output ports. In this context, we suggest a wavelength assignment procedure that improves the node performance in comparison with simple random or balanced schemes. We then address the QoS provisioning problem. While existing solutions focus on applying some forms of resource reservation on top of the contention resolution algorithm, here we propose a method based on the well-known ATM scheme of defining different service categories. In particular, we define a case study with three OPS service categories, and for each category a specific contention resolution algorithm is applied. With such a strategy the algorithms present the problem of a different performance alignment; we solve it by designing an ad hoc optical buffer architecture based on non-degenerate delays. The performance of the final node architecture is evaluated by simulation. The results obtained indicate the merits of this method, which opens up interesting future developments for a whole optical network scenario.

Measurements of very low bit-error rates for an optical packet switching node

An improvement in the accuracy of the sinusoidal interference method used to extract bit-error rates (BERs) that cannot be easily measured with conventional laboratory equipment is proposed. This technique is then used to estimate the very low BER performance of a multiple-wavelength photonic switching node for a 16-wavelength packet payload. The switching node contribution to the estimated BER is determined to be no worse than 4/spl times/10/sup -18/ from an extrapolated q-factor of 8.6.

Correction to "Ultra-Low Latency Optical Packet Switching Node"

Correction to "Ultra-Low Latency Optical Packet Switching Node"

Architecture, design, and modeling of the OPSnet asynchronous optical packet switching node

An all-optical packet-switched network supporting multiple services represents a long-term goal for network operators and service providers alike. The EPSRC-funded OPSnet project partnership addresses this issue from device through to network architecture perspectives with the key objective of the design, development, and demonstration of a fully operational asynchronous optical packet switch (OPS) suitable for 100 Gb/s dense-wavelength-division multiplexing (DWDM) operation. The OPS is built around a novel buffer and control architecture that has been shown to be highly flexible and to offer the promise of fair and consistent packet delivery at high load conditions with full support for quality of service (QoS) based on differentiated services over generalized multiprotocol label switching.

Architectures and performance of optical packet switching nodes for IP networks

As new bandwidth-hungry Internet protocol (IP) services are demanding more and more capacity, transport networks are evolving to provide a reconfigurable optical layer in order to allow fast dynamic allocation of wavelength-division-multiplexing (WDM) channels. To achieve this goal, optical packet-switched systems seem to be strong candidates as they allow a high degree of statistical resource sharing, which leads to an efficient bandwidth utilization. In this paper, we propose an architecture for optical packet-switched transport networks, together with an innovative switching node structure based on the concept of per-packet wavelength routing. The traffic performance of such node when loaded by a typical IP traffic is evaluated through computer simulation; packet loss probability and average delay performance are shown for various load conditions.

Simulation of the physical performance of optical packet switching nodes

A graphical and visual simulation system for the study of optical packet switching (OPS) nodes is accomplished. With the simulation system, the effect on physical performance — bit error rate (BER) due to a variety of factors such as the crosstalk parameters of OPS nodes, number of cascaded OPS nodes, length of optical output buffer, traffic load and fluctuation of amplitude of optical signals are evaluated. Reliability of the simulation system is proved by the analytical results obtained in all the above cases.

Study of crosstalk property in an optical packet switching node

The effect of queuing delay of output buffer on the crosstalk property in optical packet switching nodes is investigated. The relationship between crosstalk and buffer length is obtained. From the calculation and simulation results, it is concluded that the crosstalk power penalty predominantly depends on the buffer length, the longer the buffer, the greater the penalty, as well as the random range of the penalty. While comparing with the effect of queuing delay, the effect of random routing path delay takes very little proportion in the total power penalty.

Traffic management in photonic packet switching nodes by priority assignment and selective discarding

Photonic packet switching faces a major challenge in providing low packet loss probability under the constraint of shallow optical buffer depth. Although improvements have been gained by exploiting the wavelength domain through the use of WDM and wavelength conversion, performance enhancement through the use of packet priorities have yet to be investigated. This paper discusses the relationship between the inter-networking unit, optical buffering, and node control necessary to apply a reactive method of traffic management to an optical packet switching node. Analytical models, supported by simulations, for the performance of photonic switching nodes supporting packets with two levels of priority are presented. Nodes with and without optical buffers are considered. Buffer sharing among packets with different priorities backed by an early-discard mechanism is studied. The possibility of matching resource to traffic type is introduced, enabling node architectures to be designed using fewer buffers and wavelengths through optical differentiated services.

Reconfigurable optical packet header recognition and routing using time-to-wavelength mapping and tunable fiber Bragg gratings for correlation decoding

We achieve reconfigurable optical header recognition and penalty-free routing of a 2.5 Gb/s packet stream with a 1.6-ns guard time. Our method uses cross-gain compression in a semiconductor optical amplifier for time-to-wavelength mapping, and two fiber Bragg grating arrays for tunable correlation decoding. This technique may be of value in future high-speed optical packet-switching nodes.

Physical and logical validation of a network based on all-optical packet switching systems

The large growth of telecommunication traffic demand generated by multiple new applications and expected to last at least for the next decade will force telecom operators to consider offering more flexible transport services. All-optical packet switching is a powerful technique to provide this flexibility and to support in a cost-efficient way a wide range of bandwidth consuming applications. After a very brief introduction about the packet-switched network architecture studied in the framework of the ACTS KEOPS project, we describe the structure of the packet-switching node we have defined. We then move into physical and logical analysis of the network including more than 40 network sections based on 160 Gb/s throughput optical packet switching nodes could operate error free. In addition, logical simulations have proved that such networks could provide a quality of service (packet loss rate and packet transfer delay per node) compatible with a large variety of service classes. Both results validate the feasibility of the network concept and pace the way toward a flexible network based on all-optical switching techniques.

Transparent optical packet switching: the European ACTS KEOPS project approach

This paper reviews the work carried out under the European ACTS KEOPS (KEys to Optical Packet Switching) project, centering on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. The adopted approach uses optical packets of fixed duration with low bit rate headers to facilitate processing at the network/node interfaces. The paper concentrates on the networking concepts developed in the KEOPS project through a description of the implementation issues pertinent to optical packet switching nodes and network/node interfacing blocks, and consideration of the network functionalities provided within the optical packet layer. The implementation, from necessity, relies on advanced optoelectronic components specifically developed within the project, which are also briefly described.

Transparent optical packet switching: network architecture and demonstrators in the KEOPS project

This paper reviews the work carried out in the ACTS KEOPS (Keys to Optical Packet Switching) project, describing the results obtained to date. The main objective of the project is the definition, development, and assessment of optical packet switching and routing networks, capable of providing transparency to the payload bit rate, using optical packets of fixed duration and low bit rate headers in order to enable easier processing at the network/node interfaces. The feasibility of the KEOPS concept is assessed by modeling, laboratory experiments, and testbed implementation of optical packet switching nodes and network/node interfacing blocks, including a fully equipped demonstrator. The demonstration relies on advanced optoelectronic components, developed within the project, which are described.