Optical Switching Node Research Articles

End-to-End Data Flows Management in the Decentralized 5G/6G Mobile Networks

The evolution of 5G and the anticipated emergence of 6G networks demand significant enhancements in optical backhaul infrastructure to support higher bandwidth, low latency, and increased reliability. Considering a wide range of feasible applications with different quality requirements, the key challenge for the underlying backhaul and optical transport network is in the high load variance in the optical switching nodes and complicated data flows management. In this paper, a novel approach is proposed for end-to-end data flows management in decentralized 5G/6G mobile networks, which are interconnected by the optical burst switching transport infrastructure. The key idea is to train a deep recurrent neural network over a real network statistic obtain at the different network segments and service slices. Then, predictions made by deep neural network are used for predictive resource allocation in each node of the optical burst switching network to ensure a target quality of service for each end-to-end data flow. The experimental results show that proposed approach provides 90% accuracy of predictions and allows to effectively utilize the resources of optical network.

The Design of a Fiber-Coupling Micro-Lens Array for an M × N Wavelength-Selective Switch.

The M × N port wavelength-selective switch (WSS) is a crucial device used for Reconfigurable Optical Add/Drop Multiplexors and optical switching nodes in optical communication systems. The primary function of an M × N port WSS is to simultaneously transmit and switch multiple input optical signals from input fiber ports to output fiber ports through spatial light coupling. The port array module in a WSS that is responsible for coupling the spatial beam with the fiber determines the important parameters of the M × N port WSS, such as the number of input/output ports and insertion loss. In this paper, VirtualLab Fusion software 2023.1 (Build 1.558), as a powerful physical optics simulation tool, is used to design and optimize a silicon micro-lens array that can achieve the high-precision coupling of a fiber array with a pitch of 1143 μm. Finally, the designed micro-lens is manufactured and experimentally demonstrates its good beam focusing ability with a 3 dB insertion loss. The designed micro-lens array coupling system, which delivers 28 focused spots of approximately 1mm in size (the beam has a 1/e2 diameter) after transmitting a distance of around 300 mm, effectively extends the number of WSS ports. This design method of the micro-lens array significantly amplifies the port count of the M × N port wavelength-selective switch, effectively expanding it to encompass an impressive 28 × 28 ports.

Semiconductor Optical Amplifier (SOA)-Driven Reservoir Computing for Dense Wavelength-Division Multiplexing (DWDM) Signal Compensation

Optical signal processing (OSP) technology is a crucial part of the optical switching node in the modern optical-fiber communication system, especially when advanced modulation formats, e.g., quadrature amplitude modulation (QAM), are applied. However, the conventional on–off keying (OOK) signal is still widely used in access or metro transmission systems, which leads to the compatibility requirement of OSP for incoherent and coherent signals. In this paper, we propose a reservoir computing (RC)-OSP scheme based on nonlinear mapping behavior through a semiconductor optical amplifier (SOA) to deal with the non-return-to-zero (NRZ) signals and the differential quadrature phase-shift keying (DQPSK) signals in the nonlinear dense wavelength-division multiplexing (DWDM) channel. We optimized the key parameters of SOA-based RC to improve compensation performance. Based on the simulation investigation, we observed a significant improvement in signal quality over 10 dB compared to the distorted signals on each DWDM channel for both the NRZ and DQPSK transmission cases. The compatible OSP achieved by the proposed SOA-based RC could be a potential application of the optical switching node in the complex optical fiber communication system, where incoherent and coherent signals meet.

Distributed competitive satellite optical burst switching mechanism for satellite networks with ultra-high link delays

The ultra-high link latency of the conventional central reservation switching method in satellite optical networks limits link utilization. In this study, a novel fully distributed competitive satellite optical burst switching (DC-SOBS) mechanism was proposed to overcome the drawbacks of the optical circuit switching method and achieve link multiplexing. Furthermore, the proposed method addressed the low link utilization problem caused by the high link latency of the central-control-related methods. The DC-SOBS mechanism in the ring network of six Geostationary Orbit (GEO) satellites improved link utilization by three orders of magnitude compared with the reservation method. A data conflict processing method was proposed to ensure that the same information was provided to various optical switching nodes, and the same algorithm was used to achieve a consistent scheduling result in each node.

Scheduling approach for optical burst switching nodes based on hybrid multipriority algorithm

Optical burst switching (OBS) is a technique involving a switched mechanism for upcoming all-optical backhauls. However, data bursting congestion may occur as a considerable problem due to the increasing amount of light passing through interconnections and the overall system range. Moreover, the lack of restricted buffers for the infrastructure and normal one-way resource signaling exacerbates the conflict, resulting in the deletion of some contesting bursts as a response. In these types of networks, concerns related to contention can be handled by reducing congestion. In response, the quality of service (QoS) and internet connections provided must be precise and consistent. We propose a scheduling approach for satellite excitation and OBS nodes. The proposed method can satisfy the present program’s QoS, requiring a combination of duration, width hybridization limits, and prioritization scheduling. We use a dynamic barrier scheduling approach that incorporates several levels and enhances the changing efficiency compared with a particular threshold approach. To execute this design, a Xilinx xc7vx690tffg1927-2 field-programmable gate array comprises the bulk of a satellite OBS edge module. The scheduler is implemented in Verilog hardware description language and evaluated with ModelSim SE 10.6d using simulated data.

Demonstration of a Hybrid Analog–Digital Transport System Architecture for 5G and Beyond Networks

In future mobile networks, the evolution of optical transport architectures enabling the flexible, scalable interconnection of Baseband Units (BBUs) and Radio Units (RUs) with heterogeneous interfaces is a significant issue. In this paper, we propose a multi-technology hybrid transport architecture that comprises both analog and digital-Radio over Fiber (RoF) mobile network segments relying on a dynamically reconfigurable optical switching node. As a step forward, the integration of the discussed network layout into an existing mobile infrastructure is demonstrated, enabling the support of real-world services through both standard digital and Analog–Intermediate- Frequency over Fiber (A-IFoF)-based converged fiber–wireless paths. Emphasis has been placed on the implementation of a real-time A-IFoF transceiver that is employed through a single embedded fully programmable gateway array (FPGA)-based platform that serves as an Ethernet to Intermediate Frequency (IF) bridge for the transmission of legacy traffic over the analog network segment. The experimental evaluation of the proposed concept was based on the dynamic optical routing of the legacy Common Public Radio Interface (CPRI), 1.5 GBaud analog-intermediate frequency-over-fiber (A-IFoF)/mmWave and 10 Gbps binary optical waveforms, showing acceptable error vector magnitude (EVM) values for the complex radio waveforms and error-free operation for binary optical streams, with Bit Error Rate (BER) values less than 10−9. Finally, the end-to-end proof-of-concept demonstration of the proposed solution was achieved through the delivery of 4K video streaming and Internet Protocol (IP) calls over a mobile core network.

All optical metropolitan quantum key distribution network with post-quantum cryptography authentication.

Quantum key distribution (QKD) provides information theoretically secure key exchange requiring authentication of the classic data processing channel via pre-sharing of symmetric private keys to kick-start the process. In previous studies, the lattice-based post-quantum digital signature algorithm Aigis-Sig, combined with public-key infrastructure (PKI), was used to achieve high-efficiency quantum security authentication of QKD, and we have demonstrated its advantages in simplifying the MAN network structure and new user entry. This experiment further integrates the PQC algorithm into the commercial QKD system, the Jinan field metropolitan QKD network comprised of 14 user nodes and 5 optical switching nodes, and verifies the feasibility, effectiveness and stability of the post-quantum cryptography (PQC) algorithm and advantages of replacing trusted relays with optical switching brought by PQC authentication large-scale metropolitan area QKD network. QKD with PQC authentication has potential in quantum-secure communications, specifically in metropolitan QKD networks.

The Construction of High-Performance Optoelectronic Interconnection Network and the Realization of Cloud Computing for Traffic Data Recognition

Due to the problems of congestion, insufficient scalability, and high cost in the network core layer link, the network interconnection architecture needs to be optimized. The photoelectric interconnection technology has attracted the attention of many researchers with its high bandwidth, low latency, and low power consumption. In this study, after fully considering the requirements of optoelectronic switching on network node degree and processing delay and corresponding to different transmission characteristics of circuit switching and optical circuit switching, an optoelectronic interconnection architecture supporting heterogeneous network topology, namely THtop, is proposed. According to the optical circuit switching/circuit switching characteristics of the Internet, the corresponding topology structure is designed respectively in this architecture to enhance the system integration and reduce the cost. At the same time, in order to meet the requirements of wavelength and number of hops of optical circuit switching, distributed control is designed in THtop, and the design method of heterogeneous optical switching unit is introduced in the switching equipment, so that the optical switching node can further reduce the cost while playing its role. The use of high-speed optoelectronic networks will cause a large amount of traffic on the channel. In this study, the traffic identification is analyzed on the proposed THtop architecture. The Map Reduce framework in cloud computing is used as the identification model, and the K-means algorithm is taken as the identification algorithm. According to its characteristics, the W_K-means algorithm is proposed for the type identification of traffic. The results show that under the OpenNet Internet simulation environment, when the traffic is set to a certain level, more than 90% of the non-blocking network switching can be realized under the THtop architecture, and the completion time of the mouse flow and elephant flow can be significantly improved. Therefore, under the Map Reduce model, the proposed W_K -means algorithm can quickly identify different traffic types.

Hardware implementation of contention aware optical switching node for data center networks

AbstractIn the multistage bidirectional networks, the same node is accessed multiple times in the same time slot resulting in contention. In this article, we experimentally demonstrate the contention resolution with minimum electronics. This is verified in the experimental testbed and the data is switched from one node to other node without contention. The results are verified in terms of eye diagram in both the directions.

Finite/Infinite Queueing Models Performance Analysis in Optical Switching Network Nodes

In optical switching networks, optical information (packets/bursts) that are forwarded from an optical switch to another through the network could entering a queue of a certain length in each node and may be waiting inside this node before it will be transmitted to the next node. Various queueing models have been widely applied as the main tool in optical switching networks for modeling and performance evaluation analysis of the switching nodes. In this paper, studying the performance analysis of an optical switching node is discussed at Finite and Infinite queueing models to have the optimum queueing model for optical core node switch design. The waiting delay time, the average expected number of optical packets and the loss probability of packets in the optical switch are estimated at variable traffic loads and different wavelength channels.

Energy-efficient optical switching nodes based on banyan-type switching fabrics

The paper shows the possibility to reduce energy consumption in banyan-type switching fabrics working under different control algorithms. This can be done by adopting the structure of switching fabric to the intensity of traffic offered, providing lossless operation of the switching fabric at the same time. An analytical model determining the number of planes which is required for lossless servicing the offered traffic is also presented. Results obtained from the model are compared with simulation result showing high accuracy of the proposed model. The paper demonstrates also that, when using the proposed model, the amount of saved electrical energy, consumed by a switching fabric composed of switching elements based on Mach-Zhander interferometers, starts from a few watts (for switching fabric with 64 inputs) up to 1kW (for switching fabric with 1024 inputs).

Optimization of strict-sense nonblocking wavelength-space-wavelength elastic optical switching fabrics

The paper considers the optimization of strict-sense nonblocking three-stage wavelength-space-wavelength switching fabrics for elastic optical switching nodes. Strict-sense nonblocking conditions for such switching fabrics have recently been presented. A brief analysis of the number of switches required to construct such fabrics was also presented in that paper. In this paper, we present a detailed estimation of the number of elements in these switching fabrics of different capacities. To find the switching fabric with the lowest number of switching elements, all possible configurations have been checked. Such an exhaustive search was possible, since the final parameters of the switching fabric of a given capacity were found within less than a minute. The results obtained for networks of several capacities allow us to draw more general conclusions about the parameters of optimal switching fabrics.

A multicast contention resolution scheme based on shared spectrum converter for elastic optical switching node

The replication and forwarding of multicast traffic make spectrum contention probability significantly increase in elastic optical switching node. Spectrum conversion is considered as a very appealing solution to resolve spectrum contention without additional delay and traffic reordering at the receiver. In this paper, we propose a multicast switching node architecture configured with limited range spectrum converter (LRSC) and full range spectrum converter (FRSC) for elastic optical switching node. The proposed optical node architecture adopts a group of feedback shared LRSCs and a small number of output shared FRSCs to resolve optical multicast contention in frequency domain. To reduce the bandwidth blocking probability and node cost, a double weights maximal clique scheduling algorithm is designed. The number of frequency slots required by the traffic and the number of used LRSCs are considered as two weights, and graph coloring algorithm is introduced to select the scheduling scheme which uses the minimum number of LRSCs for achieving the maximum total number of frequency slots of output traffics. Simulation results show that the proposed node architecture and scheduling algorithm greatly improve the bandwidth blocking probability performance with relatively lower node cost.

Demonstration of a 3 × 4 tunable bandwidth WSS with tunable attenuation using compact spatial light paths.

M × N wavelength selective switch (WSS) is a core component to address wavelength conflict in an optical switching node. In this paper, we design and experimentally demonstrate a performance enhanced 3 × 4 tunable bandwidth WSS (TBWSS) with tunable attenuation across the full C-band, and using compact spatial light paths. Wavelength channels from any input optical fiber port can be switched into any output optical fiber port with best insertion loss (IL) of 8.4 dB and worst IL of 12.5 dB. The attenuation tuning range can reach up to 35 dB. Compared to previous demonstrations, more than 2 dB IL improvement is achieved. Based on the proposed compact spatial light paths, the number of input and output ports can be easily extended to 10 and 20, respectively.

Crosstalk-Aware Routing Spectrum Assignment and WSS Placement in Flexible Grid Optical Networks

Due to crosstalk-induced interactions among different connections, malicious high-power jamming signals can potentially spread widely in a transparent optical network. Moreover, due to imperfect port isolation in wavelength selective switches (WSSs), present within the optical switching nodes, crosstalk also affects the quality of the transmitted signal. Therefore, it is necessary to design an optical network in a way that the effect of crosstalk is minimized, while at the same time keeping the cost and the power consumption of the network low. This is achieved, in this work, by the design of appropriate WSS placement and crosstalk-aware routing and spectrum assignment algorithms in flexible grid optical networks, in the form of an integer linear program formulation and a heuristic algorithm analogous to vertex coloring. The objective of the optimization algorithms is to minimize the impact of the crosstalk effect, thus minimizing the impact to the normal operation of the network. The optimization objective is enhanced with proper functions in order to minimize the capital expenditure and the operational expenditure of the networks investigated in terms of cost and power consumption, respectively. Performance results indicate that the proposed algorithms minimize the number of WSSs required to compensate for the crosstalk effect, while only slightly increasing the spectrum utilization.

Multicast contention resolution based on time-frequency joint scheduling in elastic optical switching networks

Resolving the optical multicast contention in optical switch node is an effective approach to improve the performance of elastic optical multicast switch. An optical node architecture integrating with output shared all-optical Orthogonal Frequency Division Multiplexing (OFDM) network coding technology and shared feedback fiber delay lines (FDLs) buffer is designed. And a time-frequency joint scheduling strategy (TFJSS) is proposed. In TFJSS, the maximal weighted independent set algorithm is used to select the output packets with no overlapping spectrum among the contending multicast packets. The remaining contention packets are compressed by OFDM network coding with all-optical XOR operation. Hence, the contention is avoided in spectrum domain by encoding the contending unicast/multicast packets and changing the carrier frequency of encoded packets. If the network coding cannot successfully resolve the contending packets, the shared feedback FDLs are called to address the contention in time domain. Compared with the existing node architecture and scheduling algorithm, the simulation results show that the proposed architecture and the TFJSS can reduce the packet loss probability with low delay largely.

On blocking time in multi‐class optical burst switching nodes

SummaryRecently, there has been an increasing research interest being directed to optical burst switching (OBS) networks because of its mature electronic processing capability and high‐capacity optical transport capability. The blocking time for an OBS node, representing the time duration in which a certain channel is occupied by some class of bursts, plays an important role in characterizing the performance of an OBS network. In this paper, we analyze this important metric for an OBS node with a horizonal and a single channel theoretically and numerically. On the basis of that, the burst arrivals are assumed to follow the Poisson process and the burst lengths have a phase‐type distribution, we are able to formulate a working mechanism of an OBS node into a multilayer stochastic fluid model. Using a level crossing arguments method, we are able to obtain the Laplace–Stieltjes transforms of the blocking time, from which n‐order moments and the probability density functions of the blocking time can be further derived. We provide a numerical example to illustrate the theoretical analyses, and we further discuss the effects of the offset time and the arrival density on the blocking time through this numerical example. Copyright © 2016 John Wiley & Sons, Ltd.

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.

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.

An Approach to Resolving Contention Problem in an Optical Burst Switching WDM Network

We propose to use a new wavelength allocation (WA) scheme with deflection routing, whilst investigating its influence to the optical burst switching (OBS) node performance. To evaluate the burst blocking probability we have developed the analytical and simulation models of an OBS node performing WA scheme in conjunction with the deflection routing. The results obtained from the analytical and simulation models indicate that the WA scheme yields to decrease the deflected burst blocking probability and reduces the cost of OBS node in WDM optical network. Ill. 6, bibl. 7 (in English; summaries in English, Russian and Lithuanian).