Optical Packet Switching Node Research Articles

Architecture and Performance Evaluation of a Novel Optical Packet Switch with Input Concentrators

In this paper, we propose a novel optical packet switch (OPS) architecture with input concentrators, which employ multi-input single-output optical buffers to aggregate all the incoming traffic into a small size switching fabric. Accordingly, the physical size, the number of the needed wavelength converters, and the economic cost of the total OPS node are decreased dramatically. However, the deployment of input concentrators introduces additional packet loss and delay, except from the contention at the switch output. A Markov model is presented to study the packet loss ratio (PLR) and average packet delay given by the input concentrators. The corresponding closed form expressions are given. The model also demonstrates that the system performance can be greatly improved by increasing the buffer size when the traffic load is not larger than 0.69315. The analytical values are compared with the simulation results. All the obtained results show that the proposed model provides satisfactory approximations under different network scenarios. Moreover, the economic cost savings of the proposed OPS node at the present time and its evolution as a function of time are also discussed in detail. The proposed architecture can also be applied in a packet enhanced optical transport network (OTN).

Ultra-High-Capacity Optical Packet Switching Networks with Coherent Polarization Division Multiplexing QPSK/16QAM Modulation Formats

Optical packet switching (OPS) networks and its subsystems, like the burst-mode receiver, are an essential technology currently used in passive optical networks (PONs). Moreover, OPS may play a fundamental role on future hybrid optical circuit switching (OCS)/OPS networks and datacenter networks. This paper focuses on two fundamental subsystems of packetized optical networks: the digital coherent burst-mode receiver and the electro-optical switch. We describe and experimentally characterize a novel digital coherent burst-mode receiver that makes uses of the Stokes parametrization to rapidly estimate the state of polarization (SOP) and optimize the equalizer convergence time. This burst-mode receiver is suitable for optical packetized networks that make use of advanced modulation formats such as quadrature amplitude modulation (QAM). We study the suitability of (Pb,La)(Zr,La)O3 (PLZT) optical switches for amplitude-variable coherent polarization division multiplexing (PDM) 16QAM modulation format and demonstrate a switching capacity of 10.24 Tb/s/port. We demonstrate a full 2 × 2 OPS node with a control plane capable of solving packet contention by means of packet dropping or buffering with a switching capacity of 10.24 Tb/s/port. Finally, we demonstrate the operation of the 2 × 2 OPS node with a record capacity of 12.8 Tb/s/port plus 100 km of dispersion-compensated fiber transmission.

New time-space-time optical packet switching node based on nonlinear polarization rotation of a semiconductor optical amplifier.

In this paper, we establish a simple model to analyze the semiconductor optical amplifier's (SOA) nonlinear polarization rotation (NPR) and acquire the variable curves of phase difference between TE and TM modes with bias current, pump power, probe power, and linewidth enhancement factor (LEF). The results indicate that the optical switch based on the SOA's NPR can be realized by changing the pump's optical power and the main operating parameters, such as bias current and hold beam power, and then the pump power can be determined. On this basis, a time-space-time (T-S-T) optical packet switching node is proposed, in which the SOA's NPR switch is the basic element. Then, the T-S and S-T experimental systems are set up, and the experimental results demonstrate that the proposed switch scheme can implement the optical switching function in accordance with the routing requirement. The signal-to-noise ratio (SNR) exceeds 20 dB, and the extinction ratio (ER) is more than 10 dB after being delayed and switched in the node.

SDN-Enabled OPS With QoS Guarantee for Reconfigurable Virtual Data Center Networks

Optical packet switching (OPS) can enhance the performance of data center networks (DCNs) by providing fast and large-capacity switching capability. Benefiting from the software-defined networking (SDN) control plane, which could update the look-up-table (LUT) of the OPS, virtual DCNs can be flexibly created and reconfigured. In this work, we have implemented and assessed an SDN-based control framework for an OPS node, where the OpenFlow protocol has been extended in support of the OPS switching paradigm. Application flows are switched by the OPS at submicrosecond hardware speed, decoupled from the slower (millisecond timescale) SDN control operation. By the DCN infrastructure provider, the virtual networks become directly programmable with the abstraction of the underlying OPS node. Experimental results validate the successful setup of virtual network slices for intra-data center interconnect and quality of service (QoS) guarantee for high-priority application flows. Data plane resources are efficiently shared by exploiting statistical multiplexing. In addition, the capability of exposing per-port OPS traffic statistics information to the SDN controller enables the implementation and experimental validation of load balancing algorithms to improve the QoS performance.

A novel contention resolution scheme based on network coding for optical multicast node

Optical buffering using fiber delay lines (FDLs) has been proved to be the best choice to resolve contention for optical packet switching node. Due to the absence of optical RAM, XOR network coding becomes a new packet contention resolution technology in the all-optical networks. In this paper, we present an all-optical node architecture configured with a primary network coding module and a supplementary FDL buffer module for contention resolution. The contending packet is resolved by output shared XOR network coding module firstly without any time delay. The feedback shared FDL buffer is used to resolve the still packet contention after NC module, which is constructed by a FDL buffer loop group. Moreover, the minimum length-cascaded buffer scheduling technique (MLCBST) is designed to schedule the contending packet to available output with minimal transmission delay. The simulation results show that the proposed architecture and the MLCBST have an obvious effect on reducing the packet loss probability and decreasing the average delay for optical packet switching node.

Dynamic Load-Balancing Algorithm Incorporating Flow Distributions and Service Levels for an AOPS Node

An asynchronous optical packet-switching (AOPS) node with load-balancing capability can achieve better performance in reducing the high packet-loss ratio (PLR) and time delay caused by unbalanced traffic. This paper proposes a novel dynamic load-balancing algorithm for an AOPS node with limited buffer and without wavelength converters, and considering the data flow distribution and service levels. By calculating the occupancy state of the output ports, load state of the input ports, and priorities for data flow, the traffic is balanced accordingly. Simulations demonstrate that asynchronous variant data packets and output traffic can be automatically balanced according to service levels and the data flow distribution. A PLR of less than 0.01% can be achieved, as well as an average time delay of less than 0.46 ns.

A Fan-out Splitting Scheduling Algorithm with QoS Difference for Optical Multicast Packet Switching Node

Abstract To improve the optical multicast packet switching node throughput performance, the new multicast scheduling algorithms are need urgently to overcome the entire optical multicast packet discard under the model of “one-shot”. A novel QoS difference optical multicast scheduling algorithm, which supporting the fan-out splitting for optical multicast packet switching node with limited range wavelength converter shared per node and without optical random access memory, is presented in the paper. By dropping partly not all the optical multicast packets which are replicated in the blocking multicast source, the proposed algorithm can improve output port utilization. Moreover, the algorithm is improved to provide service QoS difference for priority different traffic application. The simulation results show that the proposed algorithms remarkably improve the throughput of optical multicast packet switch node in comparison with the existing algorithms and support high priority service with high throughput QoS.

Architecture and performance of optical packet switching router architecture for future Internet networks

This paper describes the architecture, operation and performance of an optical packet switching node prototype with 2 wavelength/channels and label swapping capabilities. Also, the main subsystems of the node to route and forward optical packets at 10 Gb/s NRZ based on the155 Mb/s 18GHz-SCM encoded label are described.

An optical packet contention resolution supporting QoS differentiation with LRWC wavelength converters for OPS

The wavelength conversion is regarded as an effective way to resolve the optical packet contention in the wavelength domain for optical packet switching. An optical packet switching node, based on shared-per-node equipped with limited range wavelength converters and parametric wavelength converters (SPN-LP), is designed to further reduce optical packet loss probability. A novel optical packet contention resolution with priority differentiation wavelength scheduling algorithm to support quality of service (QoS) for the SPN-LP architecture is put forward in the article. The simulation results show that proposed optical packet resolution enables a good QoS differentiation, namely the high priority contending optical packet has the sufficient low packet loss probability.

All-Optical Variable Buffer Based on Semiconductor Optical Amplifier

An all-optical solution for packet buffering in optical packet switching (OPS) nodes is here proposed. Discrete variable delays are obtained by exploiting an optically controlled fiber loop. Semiconductor optical amplifiers (SOAs) are used as switching gates in order to store or route the packet to the buffer output. Cross gain modulation effect is responsible for SOA-based switching, thus allowing for polarization and wavelength independent operation in the whole C-band. A maximum storage time of 50 μs is demonstrated without significant signal degradation. Performances are evaluated in terms of bit error rate measurements for 10 Gb/s non-return-to-zero data payload, providing an optical signal-to-noise ratio penalty lower than 3 dB after 10 rounds. Cross talk measurements confirm the scheme suitability for OPS applications. The proposed solution is particularly attractive in slotted OPS nodes architectures where packet contention would be managed entirely in the optical domain.

Photonic Network Technologies for New Generation Network

In this paper, we show the recent progress of photonic network technologies for the new generation network (NWGN). The NWGN is based on new design concepts that look beyond the next generation network (NGN) and the Internet. The NWGN will maintain the sustainability of our prosperous civilization and help resolve various social issues and problems by the use of information and communication technologies. In order to realize the NWGN, many novel technologies in the physical layer are required, in addition to technologies in the network control layer. Examples of cutting-edge physical layer technologies required to realize the NWGN include a terabit/s/port or greater ultra-wideband optical packet switching system, a modulation-format-free optical packet switching (OPS) node, a hybrid optoelectronic packet switching node, a packet-based reconfigurable optical add/drop multiplexer (ROADM) system, an optical packet and circuit integrated node system, and optical buffering technologies.

Performance analysis of a scalable optical packet switching architecture

We carry out the analysis of a scalable switching architecture for all-optical packet switching networks. The underlying switch is based on a 2×2 two-stage multibuffer switched delay-line-based optical switching node. By incorporating an additional bypass line and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. In this work, we develop an exact queueing model from a discrete time Markov chain (DTMC) to evaluate the system performance under bursty, nonbursty, symmetric, and asymmetric traffic conditions. The accurate deflection probability and mean packet delay are obtained from this analytical model. Furthermore, we derive an approximate analysis to calculate the lower bound of deflection probability without the heavy computational complexities incurred by the exact analytical model. Simulation results are performed to confirm the validity of our analytic models.

160-Gb/s Optical Packet Switching Subsystem With a Monolithic Optical Phased-Array Switch

1 × 8 and 1 × 16 optical packet switching (OPS) node subsystems are demonstrated. The OPS node consists of a 1 × N monolithically integrated InP optical phased-array switch, an electronic switch controller, and a label extractor/eraser that utilizes cascaded reflective fiber Bragg gratings. In-band parallel labels are employed to encode the address information. 160-Gb/s optical time-domain-multiplexed packets are dynamically switched to 8 and 16 outputs with power penalties of 0.5 and 0.7 dB, respectively.

160 Gb/s/Port 2$\,\times\,$2 OPS Node Test-Bed Performing 50 Gchip/s All-Optical Active Label Processing With Contention Detection

A 160 Gb/s/port 2×2 optical packet switching node test-bed is implemented by exploiting semiconductor optical amplifier-based label extraction and contention detection. Optical packed switched networks are attractive because they allow packet switching without conversion of the data in the electronic domain, making the nodes transparent to the data format and improving the network scalability. Despite the control of the switching and of the contentions in the network nodes can be implemented in the electronic domain, the use of all-optical processing also in the subsystems devoted to the control can increase the node performance by leading to a reduced packet latency time and to a possibly more efficient implementations. Nevertheless integrated realizations are required to make the all-optical approach attractive and effective also in terms of power consumption and footprint. SOA technology represents a mature and reliable technology suitable for hybrid integrated implementations. The implementation of active label processing in a real testbed with discrete devices demonstrates the validity of the proposed approach. Error-free operations are obtained with a 50 Gchip/s label. To the best of our knowledge this is the first demonstration of active label processing at a chip rate as high as 50 Gchip/s.

Optical Packet Switching Architecture based on Traffic Load Selective FDL Buffer Mode

Contention resolution is one of the key issues for optical packet switching (OPS). An all optical fiber delay line (FDL) shared buffering architecture based on traffic load selective FDL buffer mode was brought forward to resolve the optical packet time contention. This traffic load selective FDL buffering architecture worked as expanded output shared buffer when the traffic load of incoming OPS input port is light. When the incoming traffic load is heavy, the proposed buffering architecture worked as feedback shared buffer to allow contended packet reenter the fiber delay line to reduce packet discarded. The analysis and simulation results show that the proposed FDL buffer architecture can decrease OPS node optical packet loss probability effectively and reduce required FDL number largely.

Exact Analysis of Single-Wavelength Optical Buffers With Feedback Markov Fluid Queues

Optical buffering via fiber delay lines is used for contention resolution in optical packet and optical burst switching nodes. This article addresses the problem of exactly finding the blocking probabilities in an asynchronous single-wavelength optical buffer. Packet lengths are assumed to be variable and modeled by phase-type distributions, whereas the packet arrival process is modeled by a Markovian arrival process that can capture autocorrelations in interarrival times. The exact solution is based on the theory of feedback fluid queues for which we propose numerically efficient and stable algorithms. We not only find the packet blocking probabilities but also the entire distribution of the unfinished work in this system from which all performance measures of interest can be derived.

Advanced Subcarrier Multiplexed Label Swapping in Optical Packet Switching Nodes for Next Generation Internet Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents the recent achievements and main results of the optical packet switching node with label swapping capabilities that was developed in the framework of the IST-LABELS project. The implemented functionalities allows the routing and forwarding of optical packets at 10 Gb/s based on the information conveyed in the 18 GHz-subcarrier multiplexed (SCM) label at 155 Mb/s. Specific functions of the optical packet switching demonstrator such as label extraction and rewriting are based on high-performance fiber Bragg grating filters (FBG) whereas semiconductor optical amplifier (SOA) based wavelength conversion allows payload 2R regeneration. Advanced aspects implemented in the high speed electronic control unit such as traffic shaping, multicast, and for the first time to our knowledge, a contention resolution algorithm with priority processing are thoroughly described in this paper. This paper also presents simulations exploring the effect of these advanced features in the global performance of an optical packet switched network. In particular, we found that the contention resolution algorithm based on parallel converters with 16 wavelengths contributes to improve up to four orders of magnitude the packet loss rate for low traffic loads whereas the improvement from traffic shaping policies was of 1 order of magnitude for both low and medium traffic loads. Along with the experimental results, the feasibility of the approach as the basis for the next generation internet networks is demonstrated. </para>

ACK Packet Void Filling Priority Scheduling for Variable Length Optical Packet Switch

The excess voids are produced in the export channel with first-fit-void-filling (FF-VF) algorithm for the variable length optical packet switch (OPS). The character of void occurred in the OPS channel scheduling is analyzed. The void filling scheduling algorithm based-on ACK short length packet first is presented to decrease the average waiting time in the queue for short packet. For reducing the size of void, the hybrid buffers solution with electronic memory and fiber delay line (FDL) is used in the OPS node. The ACK packet with short length is buffered in the electronic memory, while the non-ACK packet is buffer in the FDL. When the void size on the FDL is fit for the ACK packet, the ACK packet is scheduled to FDL immediately. The results of simulation show that the proposed scheduling makes use of ACK packets first void filling scheduling mechanism to reduce FDL excess load, increases output utilization and reduce packet loss ratio for asynchronous optical network. This approach is shown to minimize the FDL numbers with the feature of high stabilization and photonic integration and to improve real time TCP traffic.

一种改进的基于反馈光缓存和反馈波长变换器的光分组交换(OPS)节点结构

The performance of an optical switching network is mainly determined by its core node structure. An improved optical packet switching (OPS) node structure based on recirculation optical fiber delay line (FDL) and feedback tunable wavelength converter (TWC), and a specific scheduling algorithm for the node structure are presented. This switching structure supports both point-to-point and point-to-multi-points broadcasting transmission with superior capacity expansion performance. Its superiority in packet loss probability is proved by simulation.

Performance Study of Optical Packet Switching Node based on Shared Wavelength Conversion

Contention resolution is one of the key issues for optical packet switching (OPS). Wavelength converter is an effective contention resolution for the contending optical packet. In this paper, an architecture model equipped with a band of shared tunable wavelength converters for optical packets node is put forward. Shared wavelength conversion corresponds to the case of a number of converters shared amongst a larger number of wavelength channels. For studying the packets blocking, we assumed packet arrivals at the optical switch with Poisson process to cope with very general traffic patterns whereas packet lengths are assumed to be exponentially distributed. The analysis and simulation results show that this architecture reduces both the packet loss ratio and the number of wavelength converters.