Optical Mesh Research Articles

Environmental Surveillance through Machine Learning-Empowered Utilization of Optical Networks.

We present the use of interconnected optical mesh networks for early earthquake detection and localization, exploiting the existing terrestrial fiber infrastructure. Employing a waveplate model, we integrate real ground displacement data from seven earthquakes with magnitudes ranging from four to six to simulate the strains within fiber cables and collect a large set of light polarization evolution data. These simulations help to enhance a machine learning model that is trained and validated to detect primary wave arrivals that precede earthquakes' destructive surface waves. The validation results show that the model achieves over 95% accuracy. The machine learning model is then tested against an M4.3 earthquake, exploiting three interconnected mesh networks as a smart sensing grid. Each network is equipped with a sensing fiber placed to correspond with three distinct seismic stations. The objective is to confirm earthquake detection across the interconnected networks, localize the epicenter coordinates via a triangulation method and calculate the fiber-to-epicenter distance. This setup allows early warning generation for municipalities close to the epicenter location, progressing to those further away. The model testing shows a 98% accuracy in detecting primary waves and a one second detection time, affording nearby areas 21 s to take countermeasures, which extends to 57 s in more distant areas.

Empowering high-dimensional optical fiber communications with integrated photonic processors

Mode-division multiplexing (MDM) in optical fibers enables multichannel capabilities for various applications, including data transmission, quantum networks, imaging, and sensing. However, high-dimensional optical fiber systems, usually necessity bulk-optics approaches for launching different orthogonal fiber modes into the optical fiber, and multiple-input multiple-output digital electronic signal processing at the receiver to undo the arbitrary mode scrambling introduced by coupling and transmission in a multi-mode fiber. Here we show that a high-dimensional optical fiber communication system can be implemented by a reconfigurable integrated photonic processor, featuring kernels of multichannel mode multiplexing transmitter and all-optical descrambling receiver. Effective mode management can be achieved through the configuration of the integrated optical mesh. Inter-chip MDM optical communications involving six spatial- and polarization modes was realized, despite the presence of unknown mode mixing and polarization rotation in the circular-core optical fiber. The proposed photonic integration approach holds promising prospects for future space-division multiplexing applications.

Theory of hydrodynamic phenomena in optical mesh lattices

Theory of hydrodynamic phenomena in optical mesh lattices

Graph wavelets for fault localization in optical mesh networks

• Real-time fault detection and localization mechanism in Elastic Optical Networks (EONs). • Alarm correlation strategies fail in the face of static threshold settings. • Detects and localizes silent network failures. • Multi-resolution analysis based on graph wavelets to address fault detection and localization problems. • Exceeds alarm based engines for fault detection and localization accuracy. EONs (Elastic Optical Networks) form the backbone of web-scale cloud infrastructure. These networks should deal with network faults and restoration in real-time with high accuracy and scalability. Thus, fault management functions to detect and localize such failures, play a critical role in modern day EONs. Network impairments are complex in nature in optical networks such as fiber losses, NLI (Non Linear Impairments) and ASE (Amplified Stimulated Emission). Currently, pre-engineered thresholds are used to detect failures in optical networks. Traditional alarm correlation strategies fail in the face of these static threshold settings. In this work, we introduce a real-time fault detection and localization mechanism, which is agnostic to such pre-engineered threshold settings. We apply multi-resolution analysis based on graph wavelets to address fault detection and localization problems. Thus, we propose to use spectrograms and wavelet coefficients to identify the irregularities in an otherwise smooth graph signal. We present a real-time fault localization analysis based on a novel Wavelet Coefficients Trail (WCT) algorithm to root-cause a client signal failure due to OSNR (Optical Signal to Noise Ratio) degradation. We apply the proposed techniques and algorithms to simulated and actual network data. Our results indicate that the proposed methods can root-cause OSNR degradation to major/minor deviations in received power on optical spans. In conclusion, we present a fault localization framework based on graph wavelets in optical mesh networks.

Supervised graph convolution networks for OSNR and power estimation in optical mesh networks

The optical signal-to-noise ratio (OSNR) and received optical channel power are critical parameters in determining the quality of transmission. The OSNR and received optical channel power are influenced by network impairments such as fiber loss, amplified stimulated emission noise, and nonlinear impairments. Furthermore, environmental effects and routing, modulation, and spectrum assignment schemes influence the OSNR and thus the reach of the optical channels. These impairments and effects vary with the spectral loads that are hard to predict in brownfield networks. Several deep neural network (DNN)-based methods have been explored to estimate the OSNR and nonlinear noise. However, these methods ignore the network topology. This paper bridges this gap by leveraging supervised graph convolution neural networks (GCNs), which operate directly on graphs for OSNR and received power estimation in an optical mesh network. We also develop and implement a novel graph windowed neural network (GWinN) to reduce the over-smoothing effects of a GCN and thus learn localized behaviors like fiber cuts. We apply a DNN, GCN, and GWinN in practice to a testbed of 8 reconfigurable optical add-drop multiplexers and 22 amplifiers. Our procedure accurately estimates the OSNR with a prediction error mean and a standard deviation of ( − 0.02 d B , 0.35 dB) for a reference OSNR ranging from (16 dB) to (24 dB).

Superfluidity of Light and Its Breakdown in Optical Mesh Lattices.

Hydrodynamic phenomena can be observed with light thanks to the analogy between quantum gases and nonlinear optics. In this Letter, we report an experimental study of the superfluid-like properties of light in a (1+1)-dimensional nonlinear optical mesh lattice, where the arrival time of optical pulses plays the role of a synthetic spatial dimension. A spatially narrow defect at rest is used to excite sound waves in the fluid of light and measure the sound speed. The critical velocity for superfluidity is probed by looking at the threshold in the deposited energy by a moving defect, above which the apparent superfluid behavior breaks down. Our observations establish optical mesh lattices as a promising platform to study fluids of light in novel regimes of interdisciplinary interest, including non-Hermitian and/or topological physics.

Multi-hop traffic grooming routing and wavelength assignment using split light trail in WDM all optical mesh networks

For the last few decades, fiber optic cables not only replaced copper cables but also made drastic evolution in the technology to overcome the optoelectronic bandwidth mismatch. Light trail concept is such an attempt to minimize the optoelectronic bandwidth gap between actual WDM bandwidth and end user access bandwidth. A light trail is an optical bus that connects two nodes of an all optical WDM network. In this paper, we studied the concept of split light trail and proposed an algorithm namely Static Multi-Hop Split Light Trail Assignment (SMSLTA), which aims to minimize blocking probability, the number of static split light trails assigned and also the number of network resources used, at the same time maximizing the network throughput. Our proposed algorithm works competently with the existing algorithms and generates better performance in polynomial time complexity.

Application of Machine Learning in Routing and Wavelength Assignment: Literature Survey

This paper presents the survey of the prominent issue in optical networks is Routing and Wavelength Assignment (RWA), due to the heavy traffic in network, there will be a need for wavelength assignment to the track in that network. The RWA problem is resolved using the approach of Genetic Algorithm and Ant Colony Optimization Algorithm, wherein up until now is noticed to be better than other optimization algorithms. By using Deep Q-Networks, a type of reinforcement learning, in optimizing the problem in selection of the routing path and wavelength assignment in an optical mesh network.

Distributed abstraction and verification of an installed optical fibre network

The management of wavelength routed optical mesh networks is complex with many potential light path routes and numerous physical layer impairments to transmission performance. This complexity can be reduced by applying the ideas of abstraction from computer science where different equipment is described in the same basic terms. The noise-to-signal ratio can be used as a metric to describe the quality of transmission performance of a signal propagated through a network element and accumulates additively through a sequence of such elements allowing the estimation of end-to-end performance. This study aims to explore the robustness of the noise-to-signal ratio metric in an installed fibre infrastructure. We show that the abstracted noise-to-signal ratio is independent of the observers and their location. We confirm that the abstracted noise-to-signal ratio can reasonably predict the performance of light-paths subsequently set in our network. Having a robust network element abstraction that can be incorporated into routeing engines allows the network management controller to make decisions on the most effective way to use the network resources in terms of the routeing and data coding format.

Assignment of dynamic light trail in WDM optical mesh networks

Light trail is a unidirectional optical bus between the source and the destination node of a WDM network. In this paper, a novel algorithm is proposed for dynamic light trail assignment, which competently works for unicast dynamic connection requests. The routing is based on Hoffman k-shortest path algorithm. The proposed algorithm is solvable in polynomial time complexity and generates better results when compared with other existing algorithms. The existing algorithms are either dependent on the complex auxiliary graph, or they have a huge run time complexity. This motivated us to lay down our research work, which is free from the complex auxiliary graph and works in lesser time complexity. The aim of the paper is to satisfy the dynamic connection requests by assigning minimum number of dynamic light trails with the objective of minimizing the blocking probability, while maximizing the capacity utilization of each dynamic light trail assigned.

Strain Gage Ramifications on Mistuning in As-Manufactured Models and Experimental Testing

Abstract Blade-mounted strain gages are vital during rig and engine development to ensure safe engine operation. However, they also enable a change in dynamics of integrally bladed rotors (IBRs). State-of-the-art IBR dynamic response predictions are accomplished using as-manufactured models (AMMs) generated via optical topography measurements and mesh morphing. Two AMM finite element models (FEMs) are created of a 20-bladed IBR. One FEM has no strain gages present, where the second FEM includes strain gages on six blades. Traditionally, strain gages and lead wires are treated as the same material property as the IBR itself. It will be shown that the inclusion of strain gages in AMM's using this method changes the IBR's predicted mistuning. An alternative AMM approach is developed that changes the material properties of the finite elements attributed to the strain gages. The predicted mistuning for each AMM is accomplished using the fundamental mistuning model identification (FMM ID), where the predicted mistuning will be compared to both traveling wave excitation (TWE) experiments and a rotating, single stage compressor rig. Findings show mistuning predictions of the nonstrain gaged AMM compare far better to the experiments compared to the inclusion of the strain gages in the AMM. Additionally, altering material properties of the strain gages in the AMM improve mistuning prediction compared to treating the strain gages as the parent IBR material. Therefore, AMM should be acquired using clean, nonstrain gaged rotors or the material properties of strain gaged elements need to be altered to more accurately model the component.

Dynamic multicast traffic grooming in light-trail WDM optical mesh networks

A light trail in a WDM optical network is an optical communication channel that allows intermediate nodes to access the channel providing the flexibility for multiplexing traffic of multiple connections into the optical communication channel at intermediate nodes. The technique of multiplexing traffic of multiple connections into a single communication channel is known as traffic grooming. This paper studies the problem of dynamic multicast traffic grooming that deals with dynamically arriving and departing multicast connections in light-trail WDM optical networks. Our objective is to reduce blocking ratio. This paper proposes an auxiliary graph model for light-trail WDM optical networks that can be used for routing and traffic grooming purposes. Based on the auxiliary graph model, two dynamic multicast traffic grooming algorithms are studied. Compared with existing algorithms in the literature, the two algorithms yield significantly better performance.

Maximizing double-link failure recovery of over-dimensioned optical mesh networks

Double-link failure models, in which any two links in the network fail in an arbitrary order, are becoming critical in survivable optical network designs. Optical networks that are over-dimensioned and purposely preplanned for full protection against any single-link failure may not survive well in an event of a double-link failure. It is therefore important to understand how much impact a subsequent second link failure may have upon traffic recovery of both failed links. This paper primarily aims to investigate traffic recoverability when a double-link failure occurs. We propose several methods for improving traffic recovery without using additional backup capacities other than the existing backup resources available for single-link failure recovery. In each proposed method, integer linear programming formulation is derived to optimize the backup resource allocation. Numerical results on various network configurations have shed some light on how network operators can choose one of five alternative methods to better handle a double-link failure. From numerical results, Method 1 offers some improvement on the traffic recoverability of the second failed link without disturbing the recovered traffic of the first failed link. Method 2 reveals that the traffic recoverability of the first failed link can be improved if the backup routes of the unrecovered traffic of the first failed link can be reassigned. Method 3 is useful for maximizing the traffic recoverability of the first failed link. Method 4 further increases the recoverability of the second failed link while maintaining the same recoverability of the first failed link as Method 3. Finally, Method 5 accomplishes the maximum overall traffic recoverability.

Corrections to “Lateral Current Spreading in III-N Ultraviolet Vertical-Cavity Surface-Emitting Lasers Using Modulation-Doped Short Period Superlattices” [Aug 18 Art. no. 2400507

There is an error in Fig. 4 of [1] in the TE 01 optical mode profile. The error is due to the author forgetting to rescale the x-axis when plotting the optical mode profile on the right y-axis. This oversight occurred because the optical mesh is different from the electrical mesh, and the correct figure is shown below. We wish to emphasize that this was merely a plotting error, and hence all of the results and conclusions presented in the manuscript remain unchanged. We sincerely regret the error.

An offline cost-efficient strategy for multicast traffic protection in WDM optical mesh networks to aid rapid recovery

The most effective way of providing popular user services such as high-definition television, video conferencing and distributed gaming over the Internet is multicasting. Protecting multicast sessions against single link failure or a fiber cut in the WDM optical backbone is thus vital. Protection schemes involve reserving resources for backup paths that remain idle during normal fault-free operation. It is thus important to design protection or survivability schemes that consume as few extra resources as possible. A number of protection schemes for multicast sessions exist in the literature but only few can provide rapid recovery. In this paper we propose a new offline strategy for ensuring survivability of multicast traffic that can aid rapid recovery from a link failure. Our strategy is designed to achieve significant resource saving while providing recovery speed comparable to 1:1 dedicated path protection. We first propose an Integer Linear Program formulation to solve the problem optimally for small networks and then a heuristic for large networks. Performance comparisons show that our heuristic performs better than two well-known heuristics and also produces near optimal results. Time complexity analysis further shows that our heuristic runs in polynomial time.

Dynamic Path Routing with Maximum Allowable p-Cycle Length and with m-Cycle in Optical Mesh Networks

During modern age, fast communication is an essential requirement of everyone and communication between large distances is mainly provided by optical mesh networks. Network failures even for a small interval lead to large disruptions in providing service of transferring of data. Therefore, for reliable network services, network survivability plays a vital role. Preconfigured protection cycle (p-cycle) combines the benefits of ring as well as mesh-based shared protection schemes which are two fundamental techniques of network survivability. Hamiltonian p-cycles (crosses every node of the network at one time) are mostly selected to achieve the level of optimal redundancy due to which the total length of the protection path may become longer than the length of the primary path, so the signal quality may fall below the desired threshold. In order to maintain required signal quality, the maximum possible length of protection path through p-cycle is to be limited. Shortest path routing (SPR) with restricted p-cycle length is mostly employed in current existing strategies of the optical networks. The monitoring cycles (m-cycles) are used for detection of fault and after that the affected service is protected which was interrupted due to span failure. This paper considers dynamic path routing (DPR) using the restricted p-cycle length with m-cycle against single-link failure. p-Cycles combined with m-cycles are used for identification of the location of the faults and its protection. An integer linear program (ILP) is expressed in optimizing the needed protection capacity with length restriction of p-cycles using DPR, and at the same time m-cycle properties are combined. Numerical results show that the total spare capacity with DPR under the maximum allowed p-cycle length combining m-cycles considering fault localization and protection is lesser than SPR.

A novel auxiliary graph model for effective dynamic traffic grooming in light-trail optical WDM mesh networks

A light trail is a unidirectional bus from a convener node to an end node. The main advantage of a light trail over a light path is that the communication channel of a light trail can be accessed by intermediate nodes providing more flexibility for traffic grooming. Several auxiliary graph models have been developed in the literature for traffic grooming in light-trail optical WDM mesh networks. These auxiliary graph models have one or more drawbacks that do not fully reflect the characteristics of a light trail. This paper develops a novel auxiliary graph model that has none of the drawbacks and is able to reflect all characteristics of a light trail. Based on the auxiliary graph model, two effective dynamic traffic grooming algorithms are proposed. The proposed dynamic traffic grooming algorithms are shown to yield low request blocking ratio.

A Closed-Form Approximation of the Gaussian Noise Model in the Presence of Inter-Channel Stimulated Raman Scattering

An accurate, closed-form expression evaluating the nonlinear interference (NLI) power in coherent optical transmission systems in the presence of inter-channel stimulated Raman scattering (ISRS) is derived. The analytical result enables a rapid estimate of the signal-to-noise ratio (SNR) and avoids the need for integral evaluations and split-step simulations. The formula also provides new insight into the underlying parameter dependence of ISRS on the NLI. The proposed result is applicable for dispersion unmanaged, ultra-wideband transmission systems that use optical bandwidths of up to 15 THz. The accuracy of the closed-form expression is compared to numerical integration of the ISRS Gaussian Noise model and split-step simulations in a point-to-point transmission, as well as in a mesh optical network scenario.

Quasi-Passive Reconfigurable Node for 5G Mobile Optical Backhaul Networks

A novel multi-dimensional quasi-passive reconfigurable (MD-QPAR) node for 5G mobile backhaul optical WDM mesh networks is proposed in this paper. The proposed MD-QPAR is capable of providing dynamic power and wavelength allocations for signals from any input port(s) to any output port(s). Each input/output port is connected to one possible direction or the local wireless nodes, and hence, the data rate, flexibility, robustness, and reliability requirements in 5G backhaul networks can be satisfied. In addition, the MD-QPAR is “quasi-passive,” where it only consumes power during network reconfigurations and there is no power consumption during steady-state operations, to enable high energy efficiency. Three possible MD-QPAR structures are proposed and studied. Simulations under the optical Flow traffic assumption are carried out and the signal blocking probability and the scalability are investigated. Proof-of-concept experiments are also undertaken and the MD-QPAR with Structure II is demonstrated. Results show that dynamic power and wavelength distributions from any input port(s) to any output port(s) can be realized, and the power penalty due to the MD-QPAR is limited to <0.5 dB.

Routing in Optical Mesh Networks - A QoS Perspective

Routing in Optical Mesh Networks - A QoS Perspective