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

We develop an integrated optical packet and circuit switching node in which signaling via optical packet switching is implemented. We demonstrate 80 (8λ × 10) Gbit/s optical packet switching with <;1E-4 packet-loss-rate, 8-lightpaths establishment, and dynamic wavelength-resources control.

We propose an asynchronous optical packet switching node architecture, where congestion resolution is based on shared optical buffers and tuneable wavelength converters. We evaluated our switch by simulations and show that decreasing packet loss probability obtained by optical buffers can be efficiently boosted by adding a few shared tuneable wavelength converters, which allows for reduction of all-optical buffer size. The smaller switch size the larger impact of wavelength conversion on packet loss probability was observed. Furthermore it can be noticed that for the proposed node architecture the higher number of buffer positions the larger improvement caused by applying tuneable wavelength converters can be achieved.

An all-optical packet switching using bistable photonic crystal nanocavity memories was demonstrated for the first time. Nanocavity-waveguide coupling systems were configured for 1 × 1, 1 × 2, and 1 × 3 switches for 10-Gb/s optical packet, and they were all operated with an optical bias power of only a few μW. The power is several magnitudes lower than that of previously reported all-optical packet switches incorporating all-optical memories. A theoretical investigation indicated the optimum design for reducing the power consumption even further, and for realizing a higher data-rate capability and higher extinction. A small footprint and integrability are also features of our switches, which make them attractive for constructing an all-optical packet switching subsystem with a view to realizing optical routing on a chip.

All-optical packet switching (AOPS) technology is essential to fully utilize the tremendous bandwidth provided by advanced optical communication techniques through forwarding packets in optical domain for the next generation network. However, long packet headers and other complex operations such as table lookup and packet header re-writing still have to be processed electronically for lack of cost-effective optical processing techniques. This not only increases system complexity but also limits packet forwarding speed due to optical-electronic-optical conversion. Lots of work of improving optical processing techniques to realize AOPS is reported in the literature. Differently, this paper proposes a new networking structure to facilitate AOPS realization and support various existing networks through simplifying networking operations. This structure only requires an AOPS node to process a short packet header to forward packets across it with neither table lookup nor header re-writing. Furthermore, it moves high layer addressing issues from packet forwarding mechanisms of routers. Consequently, any changes in addressing schemes such as address space extension do not require changes in the AOPS nodes. It can also support both connection-oriented and connectionless services to carry various types of traffic such as ATM and IP traffic. This structure is mainly based on the hierarchical source routing approach. The analytical results show that average packet header sizes are still acceptable even for long paths consisting of many nodes each of which has a large number of output ports.

A novel routing method called wavelength-separating in DWDM optical packet switching nodes for two-class priority traffic is proposed. Analysis of the method and a previous buffer-sharing method with special contention control are presented. The optimized results of two methods show that the wavelength-separating method performs better in reducing the packet loss rate (PLR) than the latter in case of with full wavelength conversion and small output buffer length.

All-optical shared-buffer packet switches have been studied intensively in literature and many scheduling algorithms have been proposed. However, these algorithms either suffer from not being able to make resource reservation, or require high time-complexity to compute scheduling assignment for packets. In this paper, we propose a fast scheduling algorithm for all-optical shared-buffer packet switches. In our algorithm, packet scheduling is first formulated as a tree-searching problem. By breaking down the search tree into multiple smaller subsets and assigning each subset to a secondary processor, solutions can be obtained in a much shorter duration since the secondary processors are working in parallel. For instance, a scheduling assignment can be calculated for a packet in 55 ns with 8 processors, and in 25 ns with 64 processors, assuming a processor clock rate of 200 MHz. We show that our algorithm can achieve a loss rate of ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> even at load 0.9 for a 32times32 switch.

Packet-switched routers need buffers during times of congestion. We show that a combined input-output queued router needs no more buffering than an output queued router. Using simulations, we show that 10-20 packet buffers are enough.

We present a 1 × 2 all-optical packet switch. All the processing of the header information is carried out in the optical domain. The optical headers are recognized by employing the two-pulse correlation principle in a semiconductor laser amplifier in loop optical mirror (SLALOM) configuration. The processed header information is stored in an optical flip-flop memory that is based on a symmetric configuration of two coupled lasers. The optical flip-flop memory drives a wavelength routing switch that is based on cross-gain modulation in a semiconductor optical amplifier. We also present an alternative optical packet routing concept that can be used for all-optical buffering of data packets. In this case, an optical threshold function that is based on a asymmetric configuration of two coupled lasers is used to drive a wavelength routing switch. Experimental results are presented for both the 1 × 2 optical packet switch and the optical buffer switch.

All-optical label swapping (AOLS) forms a key technology towards the implementation of all-optical packet switching nodes (AOPS) for the future optical Internet. The capital expenditures of the deployment of AOLS increases with the size of the label spaces (i.e. the number of used labels), since a special optical device is needed for each recognized label on every node. Label space sizes are affected by the way in which demands are routed. For instance, while shortest-path routing leads to the usage of fewer labels but high link utilization, minimum interference routing leads to the opposite. This paper studies all-optical label stacking (AOLStack), which is an extension of the AOLS architecture. AOLStack aims at reducing label spaces while easing the compromise with link utilization. In this paper, an integer lineal program is proposed with the objective of analyzing the softening of the aforementioned trade-off due to AOLStack. Furthermore, a heuristic aiming at finding good solutions in polynomial-time is proposed as well. Simulation results show that AOLStack either a) reduces the label spaces with a low increase in the link utilization or, similarly, b) uses better the residual bandwidth to decrease the number of labels even more.

We describe the dimensioning and benchmarking of packet transport networks with aggregated link capacities up to the Tbit/s range, using a circuit-switching (cross-connect) infrastructure below packet-switching nodes. The different network solutions to be evaluated are designed to carry large numbers of high-definition video and other data streams, with upper bounds on packet latency and packet loss rate for all flows. Trends of evolution are analyzed, based on a performance and cost comparison of several node architectures with different associated transport technologies (packet and circuit layers). Simulations of packet-switch nodes under pseudo-self-similar traffic, extraction of analytical models for latency and loss, end-to-end best path selection, and constrained optimization of crossconnect and packet-switch resources are combined to derive the dimensioning of all the network elements. As a result of this study, photonic cross-connects associated with carrier-grade Ethernet switches appear as the most efficient architectures, thanks to cost savings for transit traffic. Single-layer solutions involving for example only packet-switch routers turn out to be more expensive.

Since the underlying demand for network capacity can be satisfied only by extremely increasing transmission bit rate, processing speed, and switching capacity, it definitely will lead to increased power consumption of network nodes. Energy crisis is global crisis nowadays and it has brought up many problems. Power consumption is becoming a crucial issue in designing high-performance network devices. This paper studies the power consumption model of a kind of Optical Packet Switching (OPS) node based on Semiconductor Optical Amplifiers (SOA). Our results show that by dynamically adjusting the bias current of SOAs, the power consumption on an OPS node can be reduced considerably, especially when the traffic distribution across multiple ports is not balanced and inter-nodal distances vary. The total electrical power consumption can be cut off significantly. We also show the power consumption can be further reduced by jointly optimizing the thermoelectric cooler current.

Since the underlying demand for network capacity can be satisfied only by extremely increasing transmission bit rate, processing speed, and switching capacity, it definitely will lead to increased power consumption of network nodes. Energy crisis is global crisis nowadays and it has brought up many problems. Power consumption is becoming a crucial issue in designing high-performance network devices. This paper studies the power consumption model of a kind of Optical Packet Switching (OPS) node based on Semiconductor Optical Amplifiers (SOA). Our results show that by dynamically adjusting the bias current of SOAs, the power consumption on an OPS node can be reduced considerably, especially when the traffic distribution across multiple ports is not balanced and inter-nodal distances vary. The total electrical power consumption can be cut off significantly. We also show the power consumption can be further reduced by jointly optimizing the thermoelectric cooler current.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Photonic integration of an all-optical packet switch (AOPS) is a crucial issue since it leads to a great reduction of volume, power consumption, and costs. Recently, a 1<formula formulatype="inline"><tex Notation="TeX">$\, \times \,$</tex></formula>4 AOPS was successfully demonstrated by using an all-optical label extractor/eraser. The label extractor/eraser was implemented by means of fiber Bragg gratings and optical circulators that prevent the photonic integration of the AOPS. Here, we demonstrate a passive and asynchronous photonic integrated all-optical label extractor/eraser by using narrowband silicon–nitride add–drop ring-resonators. By exploiting the narrow bandwidth of the drop port and pass-through port error-free simultaneous separation/erasing of the in-band labels from the 160-Gb/s packet payload was demonstrated without noticeable pulse-shape distortions. </para>

All-optical packet switching can overcome limitations of electronic switches in terms of power consumption, speed, cost, and footprint. Switch architectures combining wavelength converters and fiber delay lines provide tunable routing and contention resolution when used with an N×N arrayed waveguide grating (AWG), a key passive optical component to bypass electronic processing limitations. An AWG passively routes either single or multiple input port wavelengths to output ports. A single wavelength per port strategy reduces crosstalk within the AWG, but drastically increases the dimensionality of the device. AWG design constraints due to bandwidth limitations and fabrication processes limit the port number for the foreseeable future to under 100. In order to scale optical switches to emerging network requirements, we must use multiple wavelengths per port. In this paper, we examine several optical router architectures for data center applications using multiple wavelengths per port, and quantify the physical layer impairments. We consider not only the AWG crosstalk, but also Q-factor degradation caused by the multiple wavelength conversions occurring when a packet is buffered for contention resolution. We present the results as a function of the number of recirculations for on–off-keying (OOK) signal formats. While previous work has addressed this issue in terms of accumulated loss, we focus on accumulated intensity noise due to crosstalk and amplified spontaneous emission (ASE). We compare the routing performance of each architecture, and we point out that the AWG crosstalk and accumulated ASE noise during packet recirculation are both critical to the routing performance.

With emerging trends for ubiquitous data services, the IP-optical convergence networks are gradually becoming a preferred technology. In optical transport networks (OTNs), a major obstacle in realizing all-optical switched IP network is due to the large processing delays of optical switching nodes that still need OEO conversion at the optical header (label) processing. The proposed labeling scheme requires neither table lookup nor label replacing in the stateless all-optical switching node, labeled packets/bursts will be forwarded through self-routing, and the only operation in optical switching nodes is to strip off its label part which represents the output port. Thus, the whole processing has been completed in the optical domain. The purposes of this paper are to shed light on a very active field of research on next generation all-IP photonics telecommunication and Internet, as well as to contribute on everyone’s modern style of living.