Optical packet switching and buffering by using all-optical signal processing methods

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.

Modeling and performance analysis of a data center network (DCN) combining optical packet switching (OPS) and agile optical circuit switching (OCS) in a unified platform are presented. Hybrid optoelectronic packet routers which combine optical switching fabric and electronic buffers are used, supporting 100 Gbit/s (25 Gbit/s × 4 wavelengths) optical packets. OCS transmission is implemented by a novel “express path,” (ExP) an instant wavelength path on demand, which enables certain flows following the ExP with no packet contention, whereas ordinary OPS packets are switched with a deflection routing algorithm and buffering for contention resolution. This architecture can support OCS for large and reliability-sensitive data transferring and OPS for latency-sensitive applications. The performance of the network is investigated via numerical simulations of top-of-rack switch (ToR)-to-ToR traffic in an N-dimensional (up to 4096 node) torus topology. We have made the following observations: 1) torus topology results in high throughput and can be scaled out by increasing the dimension; 2) contention resolution between OPS and agile OCS is needed and our proposed strategies enhance the overall performance; and 3) in a lightly to moderately loaded case of OPS traffic, more than 100 ExPs can be supported simultaneously with acceptable affect on OPS.

Optical Burst Switching and Packet Switching require the adoption of suitable contention resolution mechanisms at the optical nodes due to multiple packets/bursts attempting to access the shared output channel at the same time. Contentions can be solved by exploiting the space, wavelength and time domain. The many alternatives possible call for suitable scheduling policy aiming at an optimal system performance. This paper provides an assessment of the role of key parameters for an optical packet/burst contention resolution scheme and the resulting node cost estimation in terms of CAPEX, footprint and power consumption. Feasibility tradeoffs due to limited optical buffering and wavelength conversion capability are also taken into account.

The service evolution and the rapid increase in traffic levels fuel the interest toward switching paradigms enabling the fast allocation of Wavelength Division Multiplexing WDM channels in an on demand fashion with fine granularities (microsecond scales). For this reason, in the last years, different optical switching paradigms have been proposed (Sabella et al., 2000): optical-packet switching (OPS), optical-burst switching (OBS), wavelength-routed OBS, etc. Among the various all-optical switching paradigms, OPS attracts increasing attention. Owing to the high switching rate, Semiconductor Optical Amplifier (SOA) is a key technology to realize Optical Packet Switches. We propose some Optical Packet Switch (OPS) architectures and illustrate their realization in SOA technology. The effectiveness of the technology in reducing the power consumption is also analyzed. The chapter is organized in three sections. The main blocks (Switching Fabric, Wavelength Conversion stage, Synchronization stage) of an OPS are illustrated in Section 2 where we also show some examples of realizing wavelength converters and synchronizers in SOA technology. Section 3 introduces SOA-based single-stage and multi-stage switching fabrics. Finally the SOA-based OPS power consumption is investigated in Section 4.

Among all proposed structures for optical networks, the optical packet switching (OPS) scheme, due to its practical implementation of IPs in an optical configuration and the consequent advantages, is a prizeworthy candidate for being employed in metropolitan area network and local area network communication levels. One of the few problems frequently met using the OPS structure in the fiber-optics realm is the lack of optical buffers, thus deteriorating the system's flexibility and quality of service. For example, optical label switching networks that have been developed recently based on the generalized multiprotocol label switching protocol, profoundly suffer from this setback which is considered as a great hurdle in their evolution. In this paper, we first introduce the input and output buffer switching models while deducing their blocking probability formulations. Then, by utilizing codes in the OPS structure, we closely examine the potential of code and/or wavelength switching in packet switching networks and also determine their blocking probability. Due to close similarities between different scenarios, we present the prospect of virtual optical buffers using codes, which have close performance to input and output buffers in sight of block probability. The most significant distinction in using virtual buffers is the fact that due to their substantial nature, they happen to exhibit some error probability. However, on account of the advantageous features of codes, the simulated and formulated error probability for both coherent and noncoherent optical code division multiple access (OCDMA), such as Spectrally phase encoded OCDMA and optical orthogonal codes, using virtual buffers, tends to be negligible. Two main code and wavelength switching schemes are also brought to attention in this work, the intelligent and random methods. These scenarios demonstrate an even greater behavioral performance to that of the mere code switching scenario, leading into a more reliable adaptation of virtual buffers. In addition, simulations results happen to provide clear verifications to our analytical approach.

The present work analyzes the performance of photonic switching networks, optical packet switching (OPS) and optical burst switching (OBS), in mesh topology of different sizes and configurations. The “lossless” photonic switching node is based on a semiconductor optical amplifier, demonstrated and validated with experimental results on optical power gain, noise figure, and spectral range. The network performance was evaluated through computer simulations based on parameters such as average number of hops, optical packet loss fraction, and optical transport delay (Am). The combination of these elements leads to a consistent account of performance, in terms of network traffic and packet delivery for OPS and OBS metropolitan networks. Results show that a combination of highly connected mesh topologies having an ingress e-buffer present high efficiency and throughput, with very low packet loss and low latency, ensuring fast data delivery to the final receiver.

We propose and experimentally demonstrate a prototype 160-Gbit/s/port optical packet switch with narrow-band alloptical code-label processing, optical switching, high-extinction-ratio optical buffering, electrical scheduling, and optical MUX/DEMUX. As related technologies, we also propose and demonstrate a novel system for measuring variable-length packet BER and loss and a burst-mode optical packet 3R receiver.

In this paper, an all-optical network composed of the ROADMs (reconfigurable optical add-drop multiplexer), L2/L3 optical packet switches, and the fiber optical cross-connection for fiber scheduling and measurement based on LCoS (liquid crystal on silicon) technologies is proposed. The L2/L3 optical packet switches are designed with optical output buffers. Only the header of optical packets is converted to electronic signals to control the wavelength of input ports and the packet payloads can be transparently destined to their output ports. An optical output buffer is designed to queue the packets when more than one incoming packet should reach to the same destination output port. For preserving service-packet sequencing and fairness of routing sequence, a priority scheme and a round-robin algorithm are adopted at the optical output buffer. The wavelength of input ports is designed for routing incoming packets using LCoS technologies. Finally, the proposed OFS (optical flow switch) with input buffers can quickly transfer the big data to the output ports and the main purpose of the OFS is to reduce the number of wavelength reflections. The all-optical content delivery network is comprised of the OFSs for a large amount of audio and video data transmissions in the future.

Optical packet switch with multicast capability enables a broad range of applications in next generation optical networks. In this paper, we propose a cost-effective scheme to enhance the traffic performance of our earlier reported optical wavelength-routed multicast packet switch by modifying rather than adding multicast modules in the switch. A packet scheduling technique is introduced to substantially reduce the output contention for the switch. The effectiveness of our proposed scheme in conjunction with the scheduling technique is analyzed and validated by evaluation of packet loss performance of the modified multicast packet switch through simulations. The simulation results show that the multicast packet loss probability of the modified multicast switch can be significantly reduced without increasing the number of multicast modules by our proposed scheme. This means that to achieve an acceptable level of the multicast packet loss probability, the modified multicast switch requires fewer multicast modules in comparison with our earlier reported switch.

An optical packet and circuit integrated network (OPCInet) will allow diverse services, enhanced functional flexibility, and efficient energy consumption, as optical packet switching (OPS) and optical circuit switching (OCS) links are provided on the same infrastructure. In this paper, we design and develop a control system consisting of header processing for optical packets, signaling and routing for optical path setup, and wavelength resource control and link switching between OPS and OCS for the efficient use of resources. Our onboard optical packet header processor is capable of 16-bit longest prefix matching by embedding a 0.6W (5% of TCAM technology on the same condition), 200 million search-per-second (equivalent to 100 Gbps) forwarding engine LSI, and a statistical memory LSI for retaining the statistical information of processed headers. Reactive control automatically selects a packet or circuit link according to the statistical traffic information from the header processor and works with signaling for optical paths. We present an experimental demonstration of a new control system using a previously developed OPCInet testbed.

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.

Due to lack of optical RAM buffers in fast optical switches (FOS), statistical multiplexing technologies using FOS like Optical Burst Switching (OBS) or Optical Packet Switching (OPS) are expected to have higher data losses than conventional electronic networks. Consequently, applications transferring data by means of TCP can suffer from a lower throughput. In this paper, we show that this low-throughput problem is mainly an artifact caused by the conventional TCP congestion control algorithms, and can be remedied by using a simple yet effective stop-and-wait congestion control algorithm instead, as long as the propagation delay between TCP source and TCP destination is small compared to the transmission time of an optical packet. We show that such a condition holds for a wide range of scenarios, including fat-tree-based data center networks. We also show that the throughput achieved in a FOS network using stop-and- wait can be the same as, or higher than that in an equivalent, conventional electronic network. I. INTRODUCTION

The huge traffic growth which is currently experienced (traffic nearly doubles every year) and foreseen to continue for several years calls for high capacity networks capable of efficiently handling various types of traffic (voice, video, data). WDM (Wavelength Division Multiplexing) optical networks exploiting also fast optical packet switching are expected to provide the required capacity and flexibility for the next generation of high-speed networks. In this context, the European ACTS KEOPS project (KEys to Optical Packet Switching) has concentrated on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. Optical packets of fixed duration have been considered where the payload bit rate, which is user-dependent, can vary from a few hundred Mb/s to 10 Gb/s whereas the header is at a fixed low bit rate (622 Mb/s) to facilitate processing at the network/node interfaces. The challenge addressed by the KEOPS project was therefore to combine the advantages of the relatively coarse-grained WDM techniques with emerging all-optical switching capabilities to yield a high-throughput optical platform directly underpinning next generation data networks (ATM, IP). The project which involved nine partners (Alcatel Alsthom Recherche (F), France Telecom-CNET (F), CSELT (I), Technical University of Denmark (DK), Alcatel CIT (F), Alcatel SEL (D), University of Bologna (I), ETH-Zurich (CH) and University of Strathclyde (UK)) has addressed both network and system studies as well as demonstration experiments based on advanced optoelectronic components developed in the project in order to validate the proposed concept.

Optical packet switching (OPS) is being considered as one of the switching technologies for a future optical internet. For contention resolution in an optical packet switching (OPS) system, the wavelength dimension is generally used in combination with a fibre delay line (FDL) buffer. In this study, the authors propose to reduce the number of tunable wavelength converters (TWCs) by sharing TWCs for cost-effective design of an asynchronous OPS system with a shared or an output FDL buffer. Asynchronous and variable-length packets are considered in the OPS system design. To investigate the number of TWCs needed for the OPS system, an algorithm is proposed, which searches for an available TWC and an unused internal wavelength, as well as an outgoing channel. This algorithm is applied to an OPS system with a shared or an output FDL buffer. Also, the number of internal wavelengths (i.e. the conversion range of the TWC) needed for an asynchronous OPS system is presented for cost reduction of the OPS system.

We propose and implement an enhanced moving average (MA) based dynamic resource allocation method for optical packet and circuit integrated (OPCI) networks. In the OPCI networks, optical packet switching (OPS) and optical circuit switching (OCS) share the total bandwidth in a fiber by allocating separate wavelength resources to them. In this work, we leverage an exponential moving average (EMA) as an enhanced MA. Every time a signaling process for path establishment or release occurs at a node, the proposed method employs the EMA of number of in-use paths to reallocate wavelengths to OCS and OPS while the conventional method employs the absolute number of in-use paths. When the EMA reaches or becomes less than a threshold value, the dynamic resource allocation is executed. As results of simulations and a verification experiment, we show that the proposed method can reduce the amount of routing processes without suffering from blocking of path establishments in comparison to the conventional method. In addition, it is expected that the proposed method can effectively allocate vaster amount of bandwidth to OPS without suffering from the blocking and achieve better system performances for OPS.