Optical Packet Research Articles

Optical Packet and Circuit Integrated Networks

Optical Packet and Circuit Integrated Networks

All-optical ripple carry adder based on SOA-MZI configuration at 100 Gb/s

Ripple carry adders are broadly used for the addition of n-bit input sequences in arithmetic and logic units and for performing packet-header processing in all optical packet switched networks. In this paper, we have proposed the novel design of 2-bit ripple carry adder based on semi-conductor optical amplifier- Mach Zehnder Interferometer (SOA-MZI) configuration at 100Gb/s. The XOR, OR and AND gates have been employed as basic gates in the design of ripple carry adder. The four input signals of the adder circuit and the resultant outputs attained are at the same wavelength. The performance of the proposed device has been analyzed in terms of extinction ratio(ER), contrast ratio(CR), quality factor(QF) and amplitude modulation(AM) at the output.

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.

Optimization Technology of Optical Fiber Communication Network Based on Service Classification

Optical fiber has huge bandwidth, as a physical medium, it has good anti electromagnetic interference characteristics and excellent security performance, which is very suitable for the establishment of backbone transmission network. Wavelength division multiplexing(WDM) network based on optical fiber has been widely used. Using optical fiber for information transmission can give full play to the nearly unlimited transmission capacity of optical fiber. With the advent of the information age, data service has become the mainstream business, replacing the original telephone voice service. The great development of data transmission service further promotes the continuous development of WDM network technology. Among all kinds of services in optical network, IP service accounts for the largest proportion. In optical networks, switching is an important technology. Network performance is directly related to switching technology. With the development of optical communication technology, a variety of optical switching devices are introduced into WDM optical network, such as optical packet switching, optical burst switching and so on. This makes WDM layer have the ability of dynamic path establishment and removal similar to IP layer. In order to improve the performance of the optical network and reduce the blocking rate of the network, in WDM optical network, the services are designed in different levels. For some very important services, the highest priority is given, and the optical path channel with better survivability and higher fault tolerance is selected. For general services, it can be designed as a lower level service, and choose the appropriate optical path channel for transmission. The experimental results show that this hierarchical service design method can make more effective use of network resources, reduce the network blocking rate, and improve the overall performance of the network.

Third-order Riemann pulses in optical fibers.

We introduce the concept of third-order Riemann pulses in nonlinear optical fibers. These pulses are generated when properly tailored input pulses propagate through optical fibers in the presence of higher-order dispersion and Kerr nonlinearity. The local propagation speed of these optical wave packets is governed by their local amplitude, according to a rule that remains unchanged during propagation. Analytical and numerical results exhibit a good agreement, showing controllable pulse steepening and subsequent shock wave formation. Specifically, we found that the pulse steepening dynamic is predominantly determined by the action of higher-order dispersion, while the contribution of group velocity dispersion is merely associated with a shift of the shock formation time relative to the comoving frame of the pulse evolution. Unlike standard Riemann waves, which exclusively exist within the strong self-defocusing regime of the nonlinear Schrödinger equation, such third-order Riemann pulses can be generated under both anomalous and normal dispersion conditions. In addition, we show that the third-order Riemann pulse dynamics can be judiciously controlled by a phase chirping parameter directly included in the initial chirp profile of the pulse.

Accelerating and Decelerating Space-Time Optical Wave Packets in Free Space.

Although a plethora of techniques are now available for controlling the group velocity of an optical wave packet, there are very few options for creating accelerating or decelerating wave packets whose group velocity varies controllably along the propagation axis. Here we show that "space-time" wave packets in which each wavelength is associated with a prescribed spatial bandwidth enable the realization of optical acceleration and deceleration in free space. Endowing the field with precise spatiotemporal structure leads to group-velocity changes as high as ∼c observed over a distance of ∼20 mm in free space, which represents a boost of at least ∼4 orders of magnitude over X waves and Airy pulses. The acceleration implemented is, in principle, independent of the initial group velocity, and we have verified this effect in both the subluminal and superluminal regimes.

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.

High-Speed Wavelength Switching at TDA-DFB Laser Based on a Nonlinear Model

In order to realize a high-speed optical switch for optical packet switching (OPS), we have been focused on a wavelength routing optical switch consisting of tunable lasers and an arrayed waveguide grating (AWG), and have studied high-speed wavelength switching of a tunable distributed amplification (TDA)-distributed feedback (DFB) laser. Previously, we achieved high-speed wavelength switching by feedforward control based on linear control theory. In this article, to realize higher-speed wavelength switching, we proposed a more accurate control model based on the nonlinearity of the TDA-DFB laser. We applied our nonlinear model to 400-GHz-wide and 600-GHz-wide wavelength switching and realized high-speed wavelength switching times of 33 ns and 39 ns, respectively.

Cascadability analysis of WDM recirculating loop buffer-based switch in optical data networks

Abstract In recent years the development of cloud computing, big data, cell phone application increases day by day and this will increase the work load on the server centers. Once the network traffic increases the power consumption also increases. In recent past, for reducing this power consumption arrayed waveguide grating (AWG) based optical packet switches are proposed. In these switches the physical and network layer analysis has been presented in isolated switch. In the core network to achieve low packet loss probability an effective buffering technique is required into the design of switch. In this paper a recirculating loop buffer based switch is presented, in this switch design for sharing the recirculating buffer, WDM technology is used by the packets. The main advantage of recirculating buffer is that it allows packet priority routing and by using this technique longer duration buffering of packet is achieved. This feature provides the quality of service in optical networks. In this paper, switch is deployed in the network and the performance of switch is measured when multiple switches are cascaded in the network simultaneously. The power analysis of switch is also performed for isolated and cascaded switches. For fixing the size of the switch into the network the concept of graph theory and random graph model is used.

Hybrid buffer‐based optical packet switch with negative acknowledgment for multilevel data centers

Abstract In the present scenario, data centers serve many functionalities like storage, transfer of data, supporting web applications, etc. In data centers, various levels of hierarchy different types of switches are required; therefore, multifunctional data centers are desired. This paper discusses a novel design for optical switch which can be placed at various levels of hierarchy. In the proposed design, multifunctionality contention resolution schemes which consider electronic and optical buffering and all-optical negative acknowledgment (AO-NACK) are considered. In buffering technologies, contending packets are stored in either in electronic RAM or in fiber delay lines. In case of the AO-NACK scheme, contending packets are blocked, and a negative acknowledgment is sent back to the transmitting node and blocked packets are retransmitted. For various considered schemes, Monte Carlo simulation have been performed, results in terms of packet loss probability are presented, and it has been found that the performance of optical buffering is much superior to electronic buffering and AO-NACK schemes. It is found that, in the AO-NACK scheme, the numbers of retransmitted packets due to contention blocking are 33,304 which can be reduced to 7, by using a small amount of buffer at each node.

25.6 Tbps Capacity and Sub-µsec Latency Switching for DataCenters Using >1000-Port Optical Packet Switch Architectures

We discuss the challenges and limitations of current electrical DataCenter switches towards scaling beyond the 25.6 Tb/s capacity-era while meeting a low-latency and high-radix envelope. With the high-power SerDes and required DSP interfaces forming critical scaling factors, we discuss the perspectives and challenges of migrating to Optical Packet Switch (OPS) technologies for avoiding the electronically-induced bottlenecks, while exploiting reliable and practical techniques for overcoming well-known OPS problems, like buffering and high-port connectivity. We demonstrate the feasibility of OPS schemes by reporting experimental results of our Hipoλaos architecture towards extending its line-rate to 25 Gb/s per port and enabling 25.6 Tb/s switch capacities through a 1024-radix layout, while still preserving sub-μs latency metrics. Experimental results are presented for both unicast and multicast packets, employing the 1024-radix Hipoλaos architecture in a fully-fledged FPGA-controlled switching Plane, along with a 32 × 32 Arrayed Waveguide Grating Router (AWGR) device. The unicast performance is validated through BER measurements, while optical multicasting to 5 nodes is also experimentally evaluated at 25 Gb/s, along with an evaluation of the broadband multicast capabilities of the switch. Moreover, a mixed-traffic scenario involving both unicast and multicast traffic is demonstrated. Finally, a discussion about the perspectives and challenges of bringing OPS in DC networks is presented.

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.

A Novel Data-Aided Frame Synchronization Method Based on Hough Transform for Optical Communications

In optical communication systems, frame synchronization is essential for subsequent operations, such as error correction and payload extraction. Various methods, so far, have been proposed in the published literature, but the performance is unsatisfactory under high bit error rate (BER) conditions. We present, in this work, a novel data-aided frame synchronization technique for optical packet transmission systems, in which the transmitter sends a sequence of packets with a specific synchronization word periodically inserted, and the receiver blindly recognizes the synchronization word to attain frame synchronization. The proposed algorithm detects the synchronization word based on Hough transform (HT), a classic method for line detection in digital image processing. The core principle of the algorithm is to exploit the periodicity of the frame synchronization word, which appears as black-and-white spaced stripes on a binary image when the frames are all aligned. Simulations are conducted over a 56Gbps optical QPSK transmission system, and the results show that our algorithm is still effective in attaining frame synchronization at a BER of 0.3. A comparison is also made between our algorithm and existed autocorrelation (AC)-based algorithm. The results demonstrate that our algorithm has a better error resilience performance. When the BER is higher than 0.03, our algorithm outperforms an AC-based algorithm significantly.

Optical combinational circuit for contention detection circuit in all optical router

This paper presented an optical combinational circuit based on nonlinearities of semiconductor optical amplifier (SOA) and its associated configuration. The associated circuits used are semiconductor optical amplifier - Mach Zehnder Interferometer (SOA-MZI) and semiconductor optical amplifier plus dispersion compensation fiber (SOA + DCF) for packet contention detection. The optical combinational circuits include the optical adder connected in 2 × 2 optical node for the optical packet management. All nodes have capability of decisions and processing of incoming optical signals at 1.25 Gbps. The system performance has been evaluated and optimized by varying the SOA parameters. The proposed optical combinational circuit is also suitable for network with 3 × 3 optical node. The proposed optical combinational circuit can be verified at 10 Gbps for the next generation broadband optical network.

Hybrid and optical packet switching supporting different service classes in data center network

Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous optical–electrical–optical conversions in electronic switches, but also a decrease in network latencies due to the cut-through nature of packet transmission. However, it is adversely affected by packet contention, preventing its deployment. Solutions have been proposed to tackle the problem: addition of shared electronic buffers to optical switches (then called hybrid opto-electronic switches), customization of TCP protocols, and use of different service classes of packets with distinct switching criteria. In the context of data center networks, we investigate a combination of said solutions and show that the hybrid switch, compared to the optical switch, boosts the performance of the data center network. Furthermore, we show that introducing a “Reliable” service class improves performance for this class not only in the case of the hybrid switch, but also brings the optical switch to performance levels comparable to that of the hybrid switch, all the while keeping other classes’ performance on the same level.

Parallel Modular Scheduler Design for Clos Switches in Optical Data Center Networks

As data centers enter the exascale computing era, the traffic exchanged between internal network nodes, increases exponentially. Optical networking is an attractive solution to deliver the high capacity, low latency, and scalable interconnection needed. Among other switching methods, packet switching is particularly interesting as it can be widely deployed in the network to handle rapidly-changing traffic of arbitrary size. Nanosecond-reconfigurable photonic integrated switch fabrics, built as multi-stage architectures such as the Clos network, are key enablers to scalable packet switching. However, the accompanying control plane needs to also operate on packet timescales. Designing a central scheduler, to control an optical packet switch in nanoseconds, presents a challenge especially as the switch size increases. To this end, we present a highly-parallel, modular scheduler design for Clos switches along with a proposed routing scheme to enable nanosecond scalable scheduling. We synthesize our scheduler as an application-specific integrated circuit (ASIC) and demonstrate scaling to a 256 × 256 size with an ultra-low scheduling delay of only 6.0 ns. In a cycle-accurate rack-scale network emulation, for this switch size, we show a minimum end-to-end latency of 30.8 ns and maintain nanosecond average latency up to 80% of input traffic load. We achieve zero packet loss and short-tailed packet latency distributions for all traffic loads and switch sizes. Our work is compared to state-of-the-art optical switches, in terms of scheduling delay, packet latency, and switch throughput.

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.

Data Processing Platform of Cloud Computing and Its Performance Analysis Based on Photoelectric Hybrid Interconnection Architecture

Data processing platform is the core support platform of cloud computing. The use of electric interconnection architecture will increase the complexity of network topology, while optical interconnection architecture is ideal, so cloud computing platform based on optical interconnection has become a research hotspot. The distributed optical interconnection architecture of cloud computing data processing platform is focused on. Combining the hybrid mechanism of optical circuit switching and electric packet switching, it can meet a variety of traffic requirements. Meanwhile, it improves the switching mechanism, communication strategy, and router structure. Moreover, considering that the hybrid optoelectronic interconnection architecture can improve the network delay and throughput, but there is still a problem of network consumption. Combined with the network characteristics of the data processing platform (wireless mesh structure) of cloud computing, the network topology algorithm is studied, and the relationship between the topology and the maximum number of allocable channels is analyzed. Furthermore, the equation of topological reliability calculation is defined, and the optimization model of topological design is proposed, according to which the data processing platform of cloud computing is further optimized under the photoelectric hybrid interconnection architecture. During the experiment, before topology optimization, by changing the message length, it is found that adding optical circuit switching can help achieving large capacity and new type of transmission, and can effectively reduce the time delay. After topology optimization structure is adopted, the photoelectric hybrid-data processing platform of cloud computing without topology optimization is compared. It is found that under different reliability constraints, the throughput and end-to-end delay of the network are significantly improved, which proves that the data processing platform of cloud computing based on the photoelectric hybrid interconnection architecture is a feasible cloud computing platform.

Generation of spatiotemporal optical vortices with controllable transverse orbital angular momentum

Today, it is well known that light possesses a linear momentum which is along the propagation direction. Besides, scientists also discovered that light can possess an angular momentum (AM), a spin angular momentum (SAM) associated with circular polarization and an orbital angular momentum (OAM) owing to the azimuthally dependent phase. Even though such angular momenta are longitudinal in general, a SAM transverse to the propagation has opened up a variety of key applications [1]. In contrast, investigations of the transverse OAM are quite rare due to its complex nature. Here we demonstrate a simple method to generate a three dimensional (3D) optical wave packet with a controllable purely transverse OAM. Such a wave packet is a spatiotemporal (ST) vortex, which resembles an advancing cyclone, with optical energy flowing in the spatial and temporal dimension. Contrary to the transverse SAM, the magnitude of the transverse OAM carried by the photonic cyclone is scalable to a larger value by simple adjustments. Since the ST vortex carries a controllable OAM in the unique transverse dimension, it has a strong potential for novel applications that may not be possible otherwise. The scheme reported here can be readily adapted for the other spectra regime and different wave fields, opening tremendous opportunities for the study and applications of ST vortex in much broader scopes.