Optical Packet Switching Networks Research Articles

Spectral efficiency analysis of spectral amplitude coding-based optical packet-switching networks using p value approach

Spectral efficiency analysis of spectral amplitude coding-based optical packet-switching networks using p value approach

Operating Characteristic Curves of Optical Packet-Switching Using Optical Code-Division Multiplexing for Label Switching

In this paper, the operating characteristic curves (OCCs) of optical code-division multiplexing (OCDM) technology for label switching of an optical packet-switching (OPS) network was evaluated. A node structure for processing the packets, with spectral-amplitude-coding (SAC) labels, considering a balanced detector and an optical switch, was developed and modeled. The effects of decoding noises on the performance of both M-sequence and stuffed quadratic congruence (SQC) labeling systems were addressed. Hypothesis testing was applied to the decoder to investigate the results of label recognition. The null and alternative hypotheses were, respectively, defined as a decoder receiving the matching and mismatching labels. Due to the noise effects, the decoder output may not reflect the label status correctly. Type I error occurs when the null hypothesis is true while accepting the alternative one. Type II error occurs when the alternative hypothesis is true while accepting the null one. Analytic equations of both errors were given, considering a desired packet that was missed and an undesired packet shown in a switched path. The trade-off between these two errors, regarding the decoder threshold, was demonstrated in operating characteristic curves (OCCs). A better OCC could be found when a packet had more labeled payload bits, or when the utilized label code had a lower auto-to-cross-correlation ratio.

Coflow scheduling and placement for packet-switched optical datacenter networks

Coflow scheduling and placement for packet-switched optical datacenter networks

Analysis of phase estimation for star QAM coherent optical packet switched system

The development of data centers, 5th generation wireless network remote network education and cloud computing is increasingly demanding optical packet switched (OPS) optical interconnect networks. The blind phase estimation algorithm is one of the important phase estimation algorithms in the star QAM OPS network. However, the blind phase estimation algorithm can cause system performance degradation rapidly in the case of low signal to noise ratio (SNR). To our best knowledges, the principle and processing mechanism of the problem have not been analyzed and studied in detail. In this paper, the blind phase estimation is analyzed for the first time based on SNR and phase noise probability model at low optical signal to noise ratio. Based on the analysis, the common single differential and doubly differential coding schemes are explained for blind phase estimation. Then, the performance of the blind phase estimation + single differential and blind phase estimation + doubly differential algorithms for star QAM OPS system be compared in detail, including time-varying phase processing capability, transmission performance and tolerance to laser linewidth. The experiments be performed to verify the performance of the blind phase estimation + single differential and blind phase estimation + doubly differential algorithms.

Dynamic Wavelength Grouping for Quality of Service in Optical Packet Switching

This paper concerns Quality of Service (QoS) provisioning in Optical Packet Switching (OPS) networks. We address the topic by proposing Dynamic Wavelength Grouping (DWG) for OPS, in this technique, available wavelengths are dynamically partitioned and allocated at each network link to particular classes of service. DWG adapts to traffic fluctuations by tracking the load status of every class of traffic and then schedules optical packets over group of wavelengths assigned for each class of service. Performance is examined using an own developed simulator. This simulator models various aspects of OPS in far detail. Two network topologies are studied under various parameter settings and traffic scenarios. DWG clearly outperforms its earlier static counterpart (SWG). It appears as flexible approach, efficiently functional even when the share of the high-priority load is temporarily low. Consequently, it minimizes the total blocking probability while preserving the desired service differentiation. We report also significant improvements in the network throughput.

A Research on Key Technologies in All-Optical Label Switching Networks

With the rapid development of Internet technology, the capacity of communication system is increasing rapidly and traditional switching technology based on optical-electrical-optical (O/E/O) conversion cannot satisfy requirements for information exchange. Construction of a high-speed, large-capacity, high-bandwidth all-optical switching network will be the future direction of communication systems. In this paper, the key technologies in all-optical label switching networks are investigated. First, five kinds of optical label technologies are studied. The principles and implementation methods of them are analyzed and compared. Then, optical switching fabrics based on different kinds of optical switches are discussed. Next, a 160Gb/s Optical Time Division Multiplexing (OTDM) signal 1 × 8 packet switching experiment is introduced. Finally, the research work is summarized, and the design of core nodes in optical packet switching network is prospected.

An Application of Spectral-Amplitude-Coding Labels in Optical Signal Buffering Over Optical Packet-Switching Networks

Optical buffering is one of the essential functions in optical packet switching (OPS) network. This letter employs optical code-division multiple-access (OCDMA) signals of spectral-amplitude-coding (SAC) in a packet-buffering architecture. In the proposed scheme, the original OCDMA label of the incoming packet is identified and converted to a new label by a code-switching system. As multiple packets overlap in the time domain in a single device, SAC is adopted for packet encoding to avoid multiple access interference (MAI). The concepts of queuing system and Gaussian approximation are employed to model the buffer architecture. Simulations were conducted to demonstrate the tradeoff between packet dropping probability and the signal variations in the label identification process. The buffering performance in terms of bit-error rate (BER) is examined. The results show SAC labels perform well on packet buffering.

Complimentary code keying of spectral amplitude coding signals in optical buffering with increased capacity

Signal buffering services such as contention resolution and congestion avoidance are essential in optical packet switching networks. In this paper, an optical memory scheme based on spectral amplitude coding (SAC) and complementary code keying (CCK) is proposed to increase the buffer capacity. CCK is applied to packet buffering by selecting an available code set and encoding the payload bits with either an SAC signal or its complementarity. The capacity constraint is effectively released, as the usable codes for queuing packets are twice those for the conventional code-domain buffers. To minimize system costs by reducing the codec number, a shared structure based on an arrayed waveguide grating (AWG), which is capable of processing both the typical and complimentary coded signals simultaneously, is also investigated.

Experimental Demonstration of a Photonic Frame Based Packet-Switched Optical Network for Data Centers

This article reports on the design and the experimental realization of packet-switched optical network (PSON) for a data center network. In PSON, an optical interconnect consists of a combination of a fast tunable laser (FTL), an arrayed waveguide grating router, and a burst mode receiver (BMR). The conventional FTL transmitters can only accommodate short fixed-size photonic frame (PF) of tens of microseconds rather than variable-size PF due to the short-term wavelength stability. By using the FTL with a thermal compensation method, the PSON can support variable-size PFs with extended size to minimize the switching overhead in the optical switch domain. Our PSON system can achieve up to 96% throughput of 10 GbE service as the end-to-end optical switching time is reduced to 1.94 $\mu$ s that requires only 3 $\mu$ s guard-time in a 45 $\mu$ s time-slot. Total switching time includes wavelength conversion time of FTL, response time of BMR and burst mode-clock and data recovery (BM-CDR). Our PSON will achieve near non-blocking scheduling by use of a centralized scheduler running a grant-aware (GA) scheduling algorithm, which can be further improved to be non-blocking scheduling with a novel algorithm called C-RRP. The C-RRP scheduling algorithm is designed especially for the non-uniform distribution. Simulation results show that C-RRP improves the throughput and latency performance in hot-spot conditions.

Two-Code Keying and Code Conversion for Optical Buffer Design in Optical Packet Switching Networks

Buffering management is a crucial function in current optical packet switching (OPS) networks. To avoid packet blocking due to competition for the same switched path, optical buffering is required to queue packets after a router makes the forwarding decision. In this paper, the author proposed a buffering scheme based on optical code-division multiple access (OCDMA), where each packet is encoded with an optical signature code. An optical coding technique combining spectral-amplitude coding (SAC) and two-code keying (TCK) is introduced to advance the buffering performance regarding packet loss probability. In TCK, the payload bits “1” and “0” of a stored packet are respectively converted to a SAC signal and its complementarity. As the Hamming distance between the coding signals of bits “1” and “0” is extended, the existing drawback that the OCDMA-based buffer capacity is limited by the decoder noise increased with the number of queued SAC packets is resolved. Moreover, an encoder consisting of a fiber Bragg grating (FBG) array is applied for simplifying the system design. A SAC signal and its complementary counterpart can be generated simultaneously without the need of an extra encoder.

Multiple-Code Technique for Multi-Rate Transmissions in Optical Packet Switching Networks Based on OCDMA Labels

Supporting multi-rate transmission is an essential factor in current optical packet switching (OPS) networks. In this paper, the author studied a multi-rate scheme capable of forwarding packets with different signal rates based on label switching. The multiple-code (MC) technique was employed to label a packet by conveying its payload bits to multiple optical code-division multiple-access (OCDMA) labels. Spectral-amplitude-coding (SAC), which represents the chips in an OCDMA code as a set of wavelengths, was introduced to remove the multiple-access interference (MAI) from the overlapping among labels. The author tested the system effectiveness by conducting numerical analysis to formulate bit-error probability (BEP) and spectral efficiency (SE). The simulation results showed that the proposed network had a stable BEP performance when switching the packet flows of multiple data-rates.

Photonic-Frame-Based TCP proxy architecture in optically interconnected data center networks

Optical switching is a good candidate for achieving the key requirements of high scalability, low latency and low power consumption in future large-scale data center networks (DCNs). However, circuit-based optical switching has a disadvantage of a long reconfiguration time. Packet-based optical switching also faces challenges such as the complexity of optical header processing and the difficulty of buffering in optical switches to resolve contention. To address these problems, we present a packet-switched optical network architecture design with a photonic frame wrapper that can generate variable-size photonic frames for optically interconnected intra-DCN. The proposed architecture forms hybrid DCN architecture consisting of a flattened optical switch layer for the data path and a conventional electrical switch layer for the control path. The photonic frame wrapper can increase bandwidth utilization by minimizing guard-time insertion in the optical switch domain. We also introduce a photonic frame wrapper with proxy solution to fully exploit the gain of the proposed architecture even in inter-DCN communication with long delays, which is compliant with standard TCP instances at end nodes. In intra-DCN, the average queuing delay is analyzed to find the efficient combinations between the guard time and time-slot length for the variable-sized photonic frame. We also analyzed the bandwidth overhead of guard time, to show it is comparable to that of Ethernet based DCN. In inter-DCN, the proxy solution demonstrates a noticeable TCP performance enhancement compared with the photonic frame wrapper in terms of bandwidth efficiency and end-to-end delay by theoretical and OPNET simulation analyses.

AWG-based WDM ring networks: High-performance and low-cost system designs

Optical packet switching (OPS) ring networks are regarded as being promising solutions for future optical metropolitan area networks. In this paper, we propose novel arrayed-waveguide grating (AWG)-based wavelength division multiplexing (WDM) ring network systems that are aimed at achieving low-cost, scalable, and high-performance systems. By exploiting the cyclic routing properties and spatial wavelength reuse of a passive 2*2 AWG device, we redesign the ring network into a two-subring network, connected through the AWG device. The network is governed by a novel distributed medium access control (MAC) scheme, and we further derive a highly efficient and fair bandwidth allocation in accordance with a quota. A previously proposed experimental optical packet-switched WDM metro-ring network, called HOPSMAN, has shown to have exceptional performance among the OPS ring network studies. We show simulation and analytic results to demonstrate that our proposed system have achieved enhanced performance of the TT (tunable transmitter)-TR (tunable receiver)-based HOPSMAN by 1.5 times but have used only low-cost TT-FR (fixed-tuned receiver) or FT (fixed-tuned transmitter)-FR optical devices. Thus, the proposed networks achieve exceptional network throughput and also greatly reduce system costs.

Recirculating Buffer and Arrayed Waveguide Grating-Based Switch for Optical Data Centers

Abstract Recently, an explosive growth has been observed in data traffic, which restricts the speed of exiting data communication network. To solve such problem, fiber optical-based optical communication is preferred choice. In this paper, a switch design is proposed to tackle contention problem in Optical Packet Switching (OPS) and data center networks. The proposed switch is compared with recently proposed switch design and advantages of proposed design are presented. To show superiority of the proposed design over earlier one, mathematical modeling is presented and expressions for noise figures and Bit Error Rate (BER) are derived. Using the mathematical framework, switch analysis is done in terms of BER and packet loss probability, and it has been found that power required for correct operation of the switch is lesser in comparison to earlier one. The effect of recirculation count on packet loss probability is detailed. The network layer analysis in terms of packet loss probability is also done using Monte Carlo simulation, and relation between physical and network layer parameters is also discussed.

A survey on high-precision time synchronization techniques for optical datacenter networks and a zero-overhead microsecond-accuracy solution

A datacenter, which is a highly distributed multiprocessing system, needs to keep accurate track of time across a large number of machines. Precise time synchronization has become a critical component due to stringent requirements of several time critical applications such as real-time big data analytics, high-performance computing, and financial trading. Our study starts with a survey on the most relevant time synchronization techniques for datacenter networks. Then, we propose a zero-overhead microsecond-accuracy solution to synchronize a packet-switched optical network for datacenters. To achieve the desired time accuracy, we consider precision time protocol to synchronize the server clocks with a central controller clock. Zero-overhead is maintained by using data traffic to carry the time messages instead of a separate control channel. Through simulation, we show that microsecond level of time accuracy can be achieved. We also discuss the dependency of the accuracy on different traffic loads, traffic distributions, and packet lengths.

Recognition of the optical packet header for two channels utilizing the parallel reservoir computing based on a semiconductor ring laser

In this paper, an all-optical parallel reservoir computing (RC) system with two channels for the optical packet header recognition is proposed and simulated, which is based on a semiconductor ring laser (SRL) with the characteristic of bidirectional light paths. The parallel optical loops are built through the cross-feedback of the bidirectional light paths where every optical loop can independently recognize each injected optical packet header. Two input signals are mapped and recognized simultaneously by training all-optical parallel reservoir, which is attributed to the nonlinear states in the laser. The recognition of optical packet headers for two channels from 4 bits to 32 bits is implemented through the simulation optimizing system parameters and therefore, the optimal recognition error ratio is 0. Since this structure can combine with the wavelength division multiplexing (WDM) optical packet switching network, the wavelength of each channel of optical packet headers for recognition can be different, and a better recognition result can be obtained.

Scheduling with Machine-Learning-Based Flow Detection for Packet-Switched Optical Data Center Networks

A scalable, low-latency, high-speed, and energy-efficient data center network is a key element in the deployment of future large-scale data centers, and photonic switching has recently been recognized as a promising solution to fulfill these goals. In this study, we present a packet-switched optical network (PSON) architecture with centralized control for intra-data-center connectivity. For efficient PSON operation, intelligent yet low-complexity bandwidth-scheduling algorithms are critical. To align with realistic traffic flows in a data center, we consider “mice flow,” which occurs frequently but carries a small number of bytes, and “elephant flow,” which occurs occasionally but has a huge number of bytes. To classify traffic flows with different characteristics, we investigate various machine-learning (classification) techniques, such as C4.5 and Naïve Bayes Discretization, and compare their performance in terms of accuracy and classification speed. We also develop a priority-aware scheduling algorithm for packet switching, which is optimized for PSON, and is adaptive to flow classification under a dynamic traffic scenario. Numerical simulations show that our proposed scheduling algorithm assisted by flow-classification techniques can outperform a benchmark algorithm in terms of average delay and packet-loss ratio.

Performance of highly connected photonic switching lossless metro-access optical networks

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.

Programmable OPS/OCS hybrid data centre network

Abstract On the basis of profound understanding of data center (DC) traffic demands and optical switching technologies, we present a hybrid optical network design for future data center network (DCN). Such design integrates optical circuit switching (OCS) and optical packet switching (OPS) schemes via hybrid Top-of-the-Rack (ToR) switches which provide flexible function-switchover between different traffic patterns in the DCN. Simulations of network behaviors under such DC traffic loads indicate that the proposed OPS/OCS DCN can effectively improve the network performance. Moreover, via a preliminary analysis of OCS and OPS network configurations, the construction of hybrid DCN is also proved as the most cost- and energy-efficient way for DCN upgrading while offering a promised quality of service. An experimental demonstration shows a complete implementation of data center virtualization in the proposed hybrid data center network.

A hybrid WDM ring–tree topology delivering efficient utilization of bandwidth over resilient infrastructure

This paper proposed a hybrid WDM ring---tree topology which employs spectrally efficient 60 Gbps non-return-to-zero/polarization shift keying optical orthogonal modulated signals. The reconfigurable optical add/drop multiplexers, optical cross-connects and semiconductor optical amplifiers are utilized to make hybrid ring---tree architecture. Each optical add/drop multiplexer node is connected to tree topology to further increase the number of users. The main contribution of the proposed spectrally efficient hybrid optical network is to support the maximum number of users within limited bandwidth for future communication networks. Also, the proposed resilient ring---tree architecture has advantages such as high optical node density and bandwidth/spectral efficiency as compared to conventional packet-switched optical access network.