Optical Packet Research Articles

Two‐mode multiplexed Fourier‐based labels

AbstractA two‐mode optical packet switching architecture using an optical multiport mode‐division multiplexing label generator and processor is proposed. By combining optical labels on two modes, the number of labels is increased exponentially. Beat noise significantly affects the label error rate, when multimode crosstalk is maximum. This impairment can be mitigated by time shifting the optical labels of the two modes by half of the label duration.

An efficient and improved algorithm for generating an equivalent planar architecture of the data vortex switch

The data vortex (DV) switch was originally designed as an all optical interconnection network for high performance computing (HPC) applications. It was highly scalable with low latency and high throughput, compared to traditional switches used for optical packet switching (OPS) and HPC applications. The equivalent planar (chained MIN) model of the DV, proposed in previous literature, is a planar diagrammatic conversion of a 3-D model of the DV network. In this paper, we will focus on exploring a new, efficient and improved generalized algorithm that enables the arrangement of routing pathways to be implemented as an equivalent planar architecture (EPA, chained MIN) of a DV to find all possible routes between each source and target node pair. The original 3-D architecture of any size can be converted to a planar structure more simply by using the new generalized equivalent planar architecture (EPA) algorithm. To verify the proposed EPA algorithm, it was tested with different input traffic loads and network sizes while keeping the active angle ‘A’ constant. Network performance parameters, including injection rate (throughput) and latency (mean hops), obtained from simulation results are also provided to confirm the validity of the proposed EPA algorithm. This new algorithm is versatile, simple and can be applied to networks of various sizes.

A photonic integrated chip for distinguishing the optical wave packets based on a neural-network

In this work, we use an optical-neural network to recognize a series of optical triangular and square wave packets. This chip is designed based on the reservoir computing, consisting of the directional couplers, phase shifters, Mach-Zehnder modulators, spiral waveguide and grating couplers. The non-linear activation function is obtained by the directional couplers. The optimization of the optical reservoir computing system is performed by tuning the voltage on the phase shifters to obtain the largest extinction ratio of the output signals for different input wave packets. The photonic integrated chip is fabricated on silicon-on-insulator and is characterized at an operation frequency of 3 GHz. The results demonstrate that the photonic integrated chip can efficiently distinguish between optical triangular and square wave packets.

Secure Patient Data Monitoring and Efficient Routing Optimization using a Hyperelliptic Curve Cryptography with Fuzzy-based Priority in WBSN

Aims and Background: Wireless Body Sensor Network (WBSN) technology is one of the major research areas in the medical and entertainment industries. A wireless sensor network (WSN) is a dense sensor network that senses environmental conditions, processes, and outgoing data at the sink node. A WBSN develops patient monitoring systems that provide the flexibility and mobility needed to monitor patient health. In data communications, it is difficult to find flexible optical routing paths, switching capabilities, and packet processing in the composition of optical networks. Information-centric networks (ICNs) are a new network model and are different from information- centric models. The priority of the information-centric model is the communication network. Objectives: In the existing literature, such methods are typically developed using computationally expensive procedures, such as bilinear pairing, elliptic curve operations, etc., which are unsuitable for biomedical devices with limited resources. Using the concept of hyperelliptic curve cryptography (HECC), we propose a new solution: a smart card-based two-factor mutual authentication scheme. In this new scheme, HECC’s finest properties, such as compact parameters and key sizes, are utilized to enhance the real-time performance of an IoT-based TMIS system. Methodology: A fuzzy–based Priority Aware Data Sharing (FPADS) method is introduced to schedule the priority data and monitor the transmission length. The child node adjusts the transmission speed of the cluster head with the help of a fuzzy logic controller (FLC). Results: The proposed model estimated the traffic load of the child node and the priority of the different amounts of data to be transmitted. The principle of scheduling data packets to be developed is based on the precedence of the data with the lowest transmit length in the network. Conclusion: The proposed FPADS performance increases in terms of scheduling time utilisation, traffic distribution, and mean delay. Simulations have been done using NS2, and the outcomes have shown that the proposed methodology is efficient and improves the overall QoS of the system.

Non-compatible fully [formula omitted] symmetric Davey–Stewartson system: Localized excitation and folded solitary wave

This paper studies a non-compatible fully PT symmetric Davey–Stewartson system which models the evolution of optical wave packet in nonlinear optics. “Non-compatible” means the first two equations of the system are inconsistent that do not need to comply with extra constraint like the compatible case. We employ the multi-linear variable separation approach to derive variable separation solution for this system. The obtained solutions contain four separated free functions, render enough freedom for us to generate diverse solitons. Firstly, we construct two kinds of localized excitations: lump-lattice and periodic-lattice structure. Secondly, we obtain four typical folded solitary waves, i.e. worm-dromion shaped, fin shaped and octopus shaped waves, by introducing suitable multi-valued functions. Lastly, we systematically analyze the interaction between two and three foldons, and give the classification of it. To our knowledge, this is the first time variable separation solution been reported in PT symmetric system. The basic idea of separating variables that used in this paper can be extended to other symmetric systems.

Next Generation Exabit/s Data Center Network Supporting All Optical Circuit and Packet Switching

Next Generation Exabit/s Data Center Network Supporting All Optical Circuit and Packet Switching

Scalable and low server-to-server latency data center network architecture based on optical packet inter-rack and intra-rack switching

In this work, we introduce an efficient data center network (DCN) architecture using optical packet switching for the inter-rack and intra-rack packet networks. We investigate the end-to-end communication in a server-to-server (S2S) base, implementing the east-west networking scenario across the whole intra- and inter-rack DCN. As opposed to other optical or hybrid optical–electrical DCN studies that focus on either the intra-rack or inter-rack part of the DCN, our study proposes and investigates a unified DCN architecture that consists of three separate optical network models: the intra-rack, the inter-rack, and the bridge that connects the intra- and inter-rack networks. Particularly, the intra-rack optical network is a passive-coupler-based single-hop wavelength division multiplexing (WDM) network for the communication among servers of the same rack, following bandwidth-efficient synchronous transmission WDM access (WDMA) and time division multiplexing access (TDMA) rules. The bridge optical network is designed as a passive-optical-network-based network to connect the rack servers with the above-placed top-of-rack (ToR) switch, bridging the intra- and inter-rack optical networks and following a greedy TDMA scheme. Finally, the inter-rack optical network connects the different ToRs in a 2D torus topology over optical fibers, offering all-to-all connectivity via lightpaths that rely on a combination of spatial and wavelength paths. In our study, the DCN traffic is classified into several priority classes, each representing distinct service delay requirements, as occurs in existing DCNs. The DCN architecture design, i.e., the server and ToR switch architectures as well as the TDMA/WDMA algorithms for the intra-rack, inter-rack, and bridge optical networks, takes into consideration the traffic variability aiming to serve it into a considerably low end-to-end latency time of the order of few µs, even under high congestion conditions. The proposed DCN performance is evaluated under the scenario of 400 Gbps and 8 Tbps total capacity in the intra-rack and whole end-to-end networks, respectively, while its limitations are extensively explored. Simulation results demonstrate that our proposal achieves 90% and 100% bandwidth utilization in the optical intra- and inter-rack networks, respectively, and 91% for end-to-end S2S communication across the whole DCN. Also, the maximum end-to-end packet latency experienced across the whole DCN under highly loaded conditions is only 0.98 µs, 27 µs, and 218 µs for the highest, medium, and lower priority traffic classes, respectively, fully complying with the rigid latency requirements of various modern cloud applications such as Industry 4.0 and the Internet of Things. The proposed DCN architecture is scalable and can accommodate more than 10,000 servers. In addition, it provides a low energy footprint ensuring up to 50% power consumption reduction as compared to existing Fat-Tree DCN architectures. Finally, it provides lower end-to-end latency across the whole DCN up to high loads, as compared with other relative studies.

Congestion control analysis of optical packet switch for optical data center applications

Abstract Optical data centers serve as the backbone of modern networking, facilitating seamless connectivity for users across the globe. The connection between users and the optical data centers is established through various network topologies, which play a critical role in determining the traffic characteristics. The design and implementation of these network topologies, along with the assortment of applications hosted on optical data centers, significantly influence the flow of data within the network. The advent of cloud computing has further revolutionized optical data center operations, leading to the coexistence of a wide range of applications on different optical data center switches. As a result, the traffic characteristics observed on each optical data center switch vary significantly. This diversity in traffic patterns necessitates a comprehensive understanding of how data arrival is managed and handled by the networking infrastructure. In this paper, we explore the concept of a random traffic model for data arrival on Top of Rack (ToR) switches, which represent a crucial component of optical data center networking. In the modeling, small world model is considered. The effect of buffering and packet priorities is observed on traffic shaping. Finally, to evaluate the effectiveness of the traffic shaping techniques, we measure the packet loss performance of ToR switches and found to be as low as 10−4 even at the higher loads. Blocking performance provides valuable insights into how effectively the optical data center network manages incoming data and avoids congestion or bottlenecks.

Comparative analysis of optical data center switches

Abstract In the recent past, there has been an explosive growth in data traffic within data center systems. This rapid increase in data volume has put significant constraints on the speed of current data communication networks, which are predominantly based on electronic controllers and memory. The speed limitations of electronic devices hinder their ability to process data at higher rates efficiently. To address this issue and enable faster data processing, the use of optical communication emerges as the most promising solution. Optical communication leverages the capabilities of light signals and optical components, which can handle data at much higher rates compared to their electronic counterparts. One key element in optical communication systems is the utilization of fiber delay lines (FDLs) as optical storage for packets. FDLs offer the ability to temporarily store and delay optical signals, providing buffering capabilities within optical networks. These FDLs can be configured in various setups, including feed forward, feed backward, and recirculating configurations, each with its own set of advantages and disadvantages. In this context, this article explores several state-of-the-art arrayed waveguide grating (AWG)-based optical packet switch (OPSW) architectures. These switches are designed to efficiently route and manage optical packets within data center networks. Each architecture is summarized, highlighting its unique features and capabilities. To compare the different AWG-based OPSW architectures, various key parameters are considered, such as the cost, physical losses, bit error rate (BER), and the number of tunable components required. These parameters are critical in determining the performance, efficiency, and cost-effectiveness of the switches.

Enhancement of blue and ultraviolet components in PCF-based supercontinuum generation through inter-modal dispersive-wave radiation.

Broadband supercontinuum (SC) light sources generated through nonlinear effects in solid-core photonic crystal fibers (PCFs) have been widely used in spectroscopy, metrology, and microscopy, leading to great application successes. The short-wavelength extension of such SC sources, a longstanding challenge, has been the subject of intensive study over the past two decades. However, the exact mechanism of blue and ultraviolet light generation, especially for some resonance spectral peaks in the short-wavelength regime, is not yet fully understood. Here, we demonstrate that the effect of inter-modal dispersive-wave radiation, which results from phase matching between pump pulses at the fundamental optical mode and packets of linear waves at some higher-order modes (HOMs) propagating in the PCF core, might be one of the critical mechanisms that can result in some resonance spectral components with wavelengths much shorter than that of the pump light. We observed in an experiment that several spectral peaks resided in the blue and ultraviolet regimes of the SC spectrum, whose central wavelengths can be tuned by varying the PCF-core diameter. These experimental results can be interpreted well using the inter-modal phase-matching theory, providing some useful insights into the SC generation process.

Photonic integrated multicast switch-based optical wireless data center network

Optical wireless data center networks (OW-DCNs), which employ optical wireless technology and optical wired switching technology, are gaining interest as they promise to eliminate cable complexity, as well as to create high bandwidth interconnections and a low-cost and power-efficient system. In particular, the incorporation of optical tunable transmitters (T-TXs) and passive optical beam steering technologies is a promising way to build an OW-DCN benefitting from the potential of fast optical switching speed, low switch control complexity, and easy reconfiguration. However, the practical deployment of such an OW-DCN remains a challenge as fast (nanosecond) T-TX is required for fast optical switching operation. Implementation of fast T-TX can be realized by an array of lasers and optical gates, which are combined with photonic integration technology to achieve a compact, stable, and efficient nanosecond T-TX. In this paper, we propose an OW-DCN based on arrayed waveguide grating routers and fast T-TXs that exploit photonic integrated circuit multicast switches (PIC-MCSs). This PIC-MCS chip not only offers nanosecond-scale fast optical switching but also plays an essential role in enabling multicast operation, T-TX sharing, and dynamic bandwidth allocation between the intra- and inter-cluster networks. A 4×2 PIC-MCS has been designed, fabricated, and characterized in this proposed OW-DCN system. Experimental results validate that the proposed OW-DCN supports lossless, nanosecond, and multicast switching operation. Moreover, the dynamic bandwidth allocation and optical packet switching capability have been experimentally demonstrated. Finally, system performance with this fabricated PIC-MCS chip in a 4×4 rack OW-DCN is experimentally validated for different transmission scenarios and modulation formats. Wavelength division multiplexing multicast transmission with 50 Gb/s non-return-to-zero on–off-keying signals has been verified with less than 1.5 dB power penalty. 58 Gb/s four-level pulse-amplitude modulation transmission has also shown operation below the forward error correction threshold of 3.84×10−3 for all the different transmission scenarios.

Broadband optical packet generation by multiplexing signals using a bias tee

This paper presents a broadband optical packet generation method by multiplexing low- and high-frequency signals using a bias tee. The cut-off frequency of the bias tee, fc is optimized in terms of the eye-opening ratio for optical packet trains with different guard times and intervals. As a result, the optimal condition is observed to be fGT < fc < f1, and fc should be closer to fGT. (where fGT is the guard frequency and f1 is the high-pass cut-off frequency of a low-frequency amplifier). We implemented optical packet generation using a bias tee based on the simulation results and confirmed the effectiveness of this method.

Non-Gaussian quantum state generation by multi-photon subtraction at the telecommunication wavelength.

In the field of continuous-variable quantum information processing, non-Gaussian states with negative values of the Wigner function are crucial for the development of a fault-tolerant universal quantum computer. While several non-Gaussian states have been generated experimentally, none have been created using ultrashort optical wave packets, which are necessary for high-speed quantum computation, in the telecommunication wavelength band where mature optical communication technology is available. In this paper, we present the generation of non-Gaussian states on wave packets with a short 8-ps duration in the 1545.32 nm telecommunication wavelength band using photon subtraction up to three photons. We used a low-loss, quasi-single spatial mode waveguide optical parametric amplifier, a superconducting transition edge sensor, and a phase-locked pulsed homodyne measurement system to observe negative values of the Wigner function without loss correction up to three-photon subtraction. These results can be extended to the generation of more complicated non-Gaussian states and are a key technology in the pursuit of high-speed optical quantum computation.

Non-compatible partially [formula omitted] symmetric Davey–Stewartson system: Rational and semi-rational solution with nonzero background

The Davey–Stewartson (DS) system is an integrable extension of Schrödinger equation derived from 2 × 2 compatible linear pair, which describes the evolution of optical wave packet in nonlinear optics. This paper introduces its PT symmetric version, namely, the non-compatible partially PT symmetric DS system. “Non-compatible” means the first two equations of the system are inconsistent that the potential field does not need to satisfy certain additional constraints like the compatible case, which renders more freedom of constructing soliton solution. In addition, breather, a hybrid of breather and periodic wave are constructed via Hirota’s method. At the same time, the rational and semi-rational solutions are obtained by applying the “long wave” limit to the general form of N-soliton solution. The rational solution can be classified as lump wave, and two-extremum line rogue wave that appears either bright or dark. The semi-rational solution can be classified as a hybrid of lump wave and periodic wave, a hybrid of lump wave and Akhmediev breather, a hybrid of lump wave, Akhmediev breather, and periodic wave. The proposed technique may also help solve other nonlinear systems, and it is worth studying other symmetric reductions.

Ultra-fast broadband access and productivity: Evidence from Italian firms

We study the impact of ultra-fast broadband (UFB) infrastructures on the total factor productivity (TFP) and labor productivity of firms. We use unique balanced panel data for the 2013–2019 period on incorporated firms in Italy. Using the geographical location of the firms, we merge firm-level data with municipality-level information on the diffusion of UFB, which started in 2015. We derive consistent firm-level TFP estimates by adopting a version of the Ackerberg et al.’s (2015) method, which also accounts for firm fixed effects. We then assess the impact of UFB on productivity and deal with the endogeneity of UFB by exploiting the physical distance between each municipality and the closest optical packet backbone node. Our results show an overall positive impact of UFB on productivity. Services companies benefit the most from advanced broadband technologies, as do firms located in the North-West and South of Italy. We further decompose the impact of full-fiber networks from mixed copper-fiber connections and find that the former significantly contribute to enhancing firm productivity. Finally, by exploiting Labor Force Survey data, we provide suggestive evidence that productivity increases from UFB might be related to structural changes at the workforce level.

Origin of spectral rogue waves in incoherent optical wave packets

The rogue wave (RW) is a persistent topic in diverse fields of science including optics, hydromechanics, and electromagnetics. Despite the extensive experimental confirmations, the optical RW in the spectral domain is still elusive in aspects of its origination and evolutionary dynamics. Operating the fiber laser in a noiselike pulse (NLP) state, we observe the spectral RW according to the statistics of the shot-to-shot spectral evolution. Simulations consistent with experiments reveal that the spectrograms of NLPs are constituted by multiple localized speckles in the temporal-spectral domain, which originate from the interferences in the temporal and spectral domains. The collective motion of speckles is dominated by the Kerr effect and group-velocity dispersion. Several speckles can be in alignment at the same frequency, promoting the generation of the spectral RW. This paper sparks interest in the physics of incoherent wave packets widely existing in nonlinear optical systems.

Hybrid Optical-Electrical Data Center Networking: Challenges and Solutions for Bandwidth Resource Optimization

Fast optical switching (FOS) is the most promising technology for data center networks (DCNs) to meet data rate requirements beyond 800 Gb/s, considering its transparent modulation format, low power consumption and dense port integration. However, FOS, leveraging optical packet switching (OPS) technology, is hardly compatible with the electrical switches that are widely used in the current hybrid optical/electrical switching data center networks (Hoe-DCNs). The diversity of topologies and multi-switching granularity increases the risk of service disruption and reduces bandwidth efficiency. Based on the IP-over-OPS system, we propose bandwidth resource optimization techniques with the aid of hybrid polling contention resolution and microsecond-level load balancing in Hoe-DCNs. We first present an optical switching architecture to show its performance characteristics in the context of nanosecond-level FOSs in terms of resource management and setup optimization. Based on the fabricated FOS structure, we discuss the emerging problem of packet contention and introduce a bufferless scheduling solution. The characteristics of load balancing for Hoe-DCN are then investigated and evaluated by simulating Hoe-DCNs. Finally, the numerical results are given and analyzed based on a large-scale DCN testbed.

160 Gbps capacity and sub-us latency of polarization-independent optical packet switch architecture for free-space optical network using PLZT optical switch

In this paper, we discuss the challenges and limitations of current free-space optical (FSO) networks toward scaling beyond the 100 Gbps switch capacity era while achieving low-latency and high-reliability. Owing to the slowdown of Moore’s law, to avoid electronically-induced bottlenecks, we construct an FSO switch network and experimentally evaluate the feasibility of ultrafast optical packet switch architecture based on polarization-independent plomb lanthanum zirconate titanate (PLZT) switch without buffering. The bit error ratio of 160 Gbps ([Formula: see text]) data was validated based on measurements while still preserving the sub-us latency metrics ([Formula: see text] ns). The experimental results may offer a significant reference for FSO communication and network.

Scalable multicast control-plane for optical packet forwarding engines: A multiway SVRF approach

In control-plane of optical packet forwarding engines (OPFEs), the group-membership query algorithm determines the egress through which a packet should be forwarded. To implement a high-performance multicast-enabled switch/router, a super-fast group-membership query algorithm is the key element within the PFEs which require the following essential properties: high link-bandwidth, high port-density, high forwarding speed, high scalability, and affordable cost. Current group-membership query approaches such as Bloom filter (BF) and Scalar-Pair Vectors Routing and Forwarding (SVRF) still suffer from serious weaknesses in terms of the space/time inefficiency, false-positive error, and low maintainability, etc. To accommodate these weaknesses, we propose an improved forwarding scheme–M-way Scaler-matrix and Vectors Routing and Forwarding (M-way SVRF) by re-examining the idea of the original SVRF. The M-way SVRF divides a ρ-bit port identifier into M-sub-blocks in the memory unit, thus element's keys belonging to distinct sub-blocks are able to reuse relatively smaller identical prime keys. Compared to previous works, simulation results show that the membership queries can be partitioned to leverage task parallelism, and better performance in the aspects of memory consumption and computational complexity, especially when the port-density of optical PFE is sufficiently high.

Space-time wave packets localized in all dimensions

Optical wave packets that are localized in space and time, but nevertheless overcome diffraction and travel rigidly in free space, are a long sought-after field structure with applications ranging from microscopy and remote sensing, to nonlinear and quantum optics. However, synthesizing such wave packets requires introducing non-differentiable angular dispersion with high spectral precision in two transverse dimensions, a capability that has eluded optics to date. Here, we describe an experimental strategy capable of sculpting the spatio-temporal spectrum of a generic pulsed beam by introducing arbitrary radial chirp via two-dimensional conformal coordinate transformations of the spectrally resolved field. This procedure yields propagation-invariant ‘space-time’ wave packets localized in all dimensions, with tunable group velocity in the range from 0.7c to 1.8c in free space, and endowed with prescribed orbital angular momentum. By providing unprecedented flexibility in sculpting the three-dimensional structure of pulsed optical fields, our experimental strategy promises to be a versatile platform for the emerging enterprise of space-time optics.