Wavelength Path Research Articles

Photonic Gateway accommodating all types of wavelength paths for digital-coherent and IM-DD user terminals in all-photonic metro-access converged networks

In access and metro networks, there is increasing demand for guaranteed wide-bandwidth and stringent/deterministic end-to-end latency characteristics. Converging these networks by expanding dense wavelength-division-multiplexed metro networks to access areas is a promising approach to satisfy this demand. An All-Photonics Metro-Access Converged Network (APN) dynamically and flexibly provides a wavelength connection between any two points including user premises. This evolution in network architecture presents some technical challenges. First, from the access-node architecture viewpoint, conventional reconfigurable optical add/drop multiplexers (ROADMs) do not have functions for remote and in-channel user-terminal (UT) control or turn-back connection within the access area. Therefore, the APN cannot be achieved by simply adopting ROADMs as access nodes, which are defined as Photonic Gateways. Remote and in-channel UT controls are required to control the endpoints of a wavelength path beyond the carrier control-plane network. These types of control should be independent of the protocol and modulation/detection method for the main signal. In addition, the Photonic Gateway must flexibly and efficiently support a new type of wavelength path, specifically a turn-back connection within the access area, due to metro/access convergence. Second, from the viewpoint of the process for dynamic wavelength-path provisioning, the APN controller should autonomously discover physical connectivity between a UT and the Photonic Gateway connected via field access fibers. This paper proposes a novel Photonic Gateway architecture that flexibly and scalably provides various UTs with direct optical connections including turn-back configurations. This paper also proposes a method that autonomously recognizes physical connections between newly connected UTs and the Photonic Gateway. The proposed architecture and method are experimentally verified based on all types of wavelength-path provisioning that take at most 72 s using Photonic Gateway prototypes, 100-Gb/s digital-coherent UTs, and 10-Gb/s intensity-modulation direct-detection UTs. All types of wavelength paths that are provided over the APN architecture are considered including a turn-back connection between two UTs within the same access area and connections between two UTs that traverse the metro area with or without optical/electrical conversion.

Obtaining the circular polarization in a nano-dielectric resonator antenna for photonics applications

A technique is implemented for obtaining the circular polarization in a nano-dielectric resonator (DR) antenna. A cylindrical DR has been excited by a nanostrip feedline. The application of input Gaussian pulse at the corner of feedline splits the field components into two parts. These field components travel at the edges of the feedline with a quarter wavelength path difference between them. The coupling of these field components to DR provides the circularly polarized response. The antenna is designed for operating in the optical C-band. The proposed antenna provides the 10 dB impedance bandwidth of 11.58% (187–210 THz) and 3 dB axial ratio bandwidth of 5.72% (188.5–199.6 THz).

Resource optimization of optical aggregation network for efficient software-defined datacenters

Software-defined datacenters (SDDCs) have recently received much attention for rapid delivery of cloud-based applications. In this paper, we consider the design of an optical aggregation network for cost-efficient software-defined datacenters (SDDCs). Here, an optical aggregation network connects a server accommodating virtual network functions (VNFs) with access gateway nodes (AGNs) via a time-division-multiplexing (TDM)-based point-to-multipoint (P2MP) wavelength path to aggregate traffic from geographically distributed end users to cloud datacenters. Each VNF must be placed on an adequate server in consideration of the efficiency of wavelength paths to reduce network cost for cloud access. However, existing VNF placement algorithms determine VNF placement without considering the efficiency of wavelength paths, which deteriorates network performance and increases network cost. To solve this problem, VNFs must be placed so that a P2MP wavelength path can be efficiently shared by multiple AGNs to reduce network cost. For this purpose, we propose a VNF placement algorithm, called the decomposition-based VNF placement algorithm (DVA), in a TDM-wavelength-division-multiplexing (WDM)-based optical aggregation network for cost-efficient SDDCs. DVA can find approximate solutions of sufficient quality within practical computation time.

Compact acoustic lens composed of annular cavities covered by a membrane

A thin planar acoustic lens composed of concentric annular slits on a circular steel plate covered by a membrane made up of aluminum foil is numerically designed, and its performance in focusing low-frequency sound in air is experimentally demonstrated. Resonant fundamental modes of the membrane-backed cavities are calculated via the Finite-Element Method. By carefully adjusting the radii of the concentric cavities, the phase discontinuity across the cavities can be employed to achieve constructive interference of sound waves at a focal length of 200 mm, which is close to the acoustic wavelength, at 2190 Hz. The designed lens has an overall radius which is approximately one fourth of the radius of a conventional acoustic Fresnel lens employing a wavelength path length difference between adjacent cavities.

A VCSEL-based backbone extended-reach optical fibre network: Supporting up to 10 Gbps flexible access networks for Africa

Abstract In this paper, using vertical cavity surface-emitting lasers (VCSELs) and Raman amplification, a low power consuming, energy-efficient and cheap technique to transmit high speed data signals over optical fibre is experimentally demonstrated. Several channels are joined through dense wavelength division multiplexing (DWDM) technique and transmitted over a single fibre link. With a 24.7 dBm forward Raman pump, a 8 dB flat gain is distributed over a spectral width of 5.2 nm (650 GHz). Moreover, different wavelength paths are realized by tuning the emission of the VCSEL from 1546.8 nm to 1552 nm while adjusting its bias currents. In realizing extended-reach, two DWDM/flexible channels spaced at 50 GHz and with each transmitting at 10 Gbps have been transmitted for 76.8 km while incurring a 3.2 dB power penalty as measured at a bit-error-rate (BER) threshold of 10−9. In a typical network, the wavelength adjustment of the VCSEL avoids incidences of denial of service whenever there is either fibre-cuts, increased network traffic or channel collisions. Finally, by combining Raman amplification and chromatic dispersion mitigation using negative dispersion shifted fibres, this work presents robust VCSEL-based technique that is tailored to provide 10 Gbps per channel for backbone optical fibre supporting long-haul access networks in Africa.

TSDX: Enabling Impairment-Aware All-Optical Inter-Domain Exchange

Optical transmission systems exist ubiquitously in data center, access, metro and long-haul networks, and are divided into different autonomous domains based on different carrier ownership, network equipment manufacturers, geographical location, etc. Software-defined Internet exchange methods have been proposed to solve the long-standing problem of inter-domain routing and enable control flexibility in layer-3 networks, and software-defined networking (SDN) has also been introduced to optical networks and much progress has been made to enhance optical network control capability. In this paper, we investigate a transparent software-defined exchange (tSDX) with real-time impairment-aware service level agreement (SLA) guarantees for multidomain optical networks. An SDN-based hierarchical control architecture is designed and implemented. End-to-end, impairment-aware wavelength path provisioning is experimentally realized in a multidomain network. Real-time optical signal to noise ratio based optical performance monitoring, together with inter-domain negotiation enabled by our proposed SDN control architecture, serves as an SLA guarantee for 100-Gbps polarization-multiplexed quadrature phase-shift keying signals in dense wavelength division multiplexed transmission.

Energy Efficient Dynamic Optical Routing for Mobile Metro-Core Networks Under Tidal Traffic Patterns

In general, humans follow highly predictable daily movements. We commute from residential to working and/or educational areas in a daily basis, and we have a selection of commercial and recreational areas for the nights and weekends. We also use the mobile phone at regular hours, for example when commuting, during lunch break and at night. Such regular behavior creates predictable spatio-temporal fluctuations of traffic patterns, which in analogy to the periodical rise and fall of the sea levels, its known as tidal traffic phenomenon. In this paper, we propose a suite of on-line matheuristics to reduce energy consumption of optical layer in mobile metro-core networks, while providing 1 + 1 protection of the aggregated traffic. The proposed matheuristic dynamically optimizes resource allocation by effectively adapting to predictable tidal traffic variations. The optimality of on-line decisions is achieved by generating optimal weighted graphs from the interaction with an off-line optimization phase. In the off-line phase either a wavelength path (WP) or a virtual-WP problem is solved using the regular tidal traffic patterns. Our results display energy savings of more than 20% by introducing load adaptive network operation, while the matheuristic closely follows the optimal results. We also introduce a heuristic method to reduce service disruption due to routing changes, while preserving energy saving capability. The heuristic allows us to reduce service disruption in the range of 38–80% with a small penalty on energy saving of less than 5%.

OPS/Agile-OCS Data Center Network With Flow Management

Modeling and performance analysis of a data center network (DCN) combining optical packet switching (OPS) and agile optical circuit switching (OCS) in a unified platform are presented. Hybrid optoelectronic packet routers which combine optical switching fabric and electronic buffers are used, supporting 100 Gbit/s (25 Gbit/s × 4 wavelengths) optical packets. OCS transmission is implemented by a novel “express path,” (ExP) an instant wavelength path on demand, which enables certain flows following the ExP with no packet contention, whereas ordinary OPS packets are switched with a deflection routing algorithm and buffering for contention resolution. This architecture can support OCS for large and reliability-sensitive data transferring and OPS for latency-sensitive applications. The performance of the network is investigated via numerical simulations of top-of-rack switch (ToR)-to-ToR traffic in an N-dimensional (up to 4096 node) torus topology. We have made the following observations: 1) torus topology results in high throughput and can be scaled out by increasing the dimension; 2) contention resolution between OPS and agile OCS is needed and our proposed strategies enhance the overall performance; and 3) in a lightly to moderately loaded case of OPS traffic, more than 100 ExPs can be supported simultaneously with acceptable affect on OPS.

Sub-lambda and Wavelength Path Reconfiguration in Multi-layer Transport Networks [Invited

We investigate adaptive reconfiguration of sub-lambda and wavelength paths to deal with unpredictable traffic demands. To accommodate traffic effectively, wavelength paths need to be reconfigured cooperatively with sub-lambda paths while minimizing the number of migration sequences. Therefore, we propose a scheme for sub-lambda and wavelength path reconfiguration based on wavelength resource management in multi-layer transport networks. Three steps comprise the proposed scheme: wavelength resource management, reconfiguration trigger, and reconfiguration. First, management of the number of wavelength paths that can be accommodated between all node pairs is calculated for each path accommodated. Second, if that number is less than the threshold value set in advance for some node pair, reconfiguration is performed. Third, the sub-lambda and wavelength paths are reconfigured. In this scheme, we also propose a sub-lambda path reconfiguration algorithm that reconfigures multi-hop sub-lambda paths to single-hop paths first, and two wavelength path reconfiguration algorithms that reduce wavelength fragmentation and the number of migration sequences considering the accommodation rate. Numerical evaluation shows that the number of fibers is suppressed by 12%–14% and that the equipment cost is reduced by approximately 8%–9% compared to when no reconfiguration is used. The results also show that the number of migration sequences for the wavelength defragmentation algorithms is reduced by approximately 23%–35% compared to that for the conventional algorithm.

Interdomain wavelength path control for translucent wavelength switched optical networks: from rationales to experiments

A translucent wavelength switched optical network (WSON), with sparse 3R regenerators to guarantee the signal quality of an optical connection, is a promising paradigm for a metro/ core network. This is because a translucent WSON can achieve performance comparable to that of an all-electronic switching (i.e., opaque) network with far lower network cost and a great reduction in power consumption. Because of its advantages, many recent research and standardization efforts have focused on translucent WSONs. However, most of them study the intradomain case, and issues related to multidomain translucent WSONs are largely open at present. In light of this, in this article, we present two possible strategies to improve interdomain path computation and lightpath establishment in a multidomain translucent WSON. Both approaches are experimentally demonstrated and quantitatively evaluated. Our aim is to provide feasible and efficient solutions for supporting a multidomain translucent WSON, as well as to obtain valuable insight into the proposed strategies through experiments, which will be beneficial for the potential industrial deployment of translucent optical networks.

Load-Balanced Fixed Routing for Wavelength Routed Optical Networks

Due to simplicity in lightpath service provisioning, fixed shortest path routing is considered as one of major provisioning strategies in the wavelength routed optical networks. Nonetheless, the employment of fixed shortest routes can cause unbalanced network traffic load distribution and consequentially lead to network congestion. In this paper, we propose a novel Load-Balanced Fixed Routing (LBFR) scheme that can avoid network congestion and retain the operational simplicity of fixed routing. A pre-training process based on a forecasted traffic load matrix is employed to find a (or few) fixed route(s) between each pair of nodes for lightpath service provisioning. For a wavelength path (WP) network subject to the constraint of wavelength continuity, we also develop an analytical model that can effectively estimate lightpath blocking performance under multiple fixed routes between each pair of nodes. Results show that the proposed LBFR can perform much better than traditional fixed shortest path routing in lightpath blocking, and performance improvement becomes more significant with an increasing network nodal degree.

Effects of Wavelength and Optical Path Length in Design of Fingernail Touch Force Sensing

This paper experimentally identifies the optimal optical parameters for the transmittance of light through the human fingernail bed to measure the change in blood volume beneath the fingernail, which is directly related to touch forces exerted on the fingertip. When forces are applied to the fingertip, various red and white coloration regions occur along the fingernail area, hence the transmittance of light through the fingernail bed is a function of applied force. The fingernail sensor uses optical reflectance photoplethysmography to measure the change in blood perfusion in the fingernail bed where an array of LEDs and photodetectors is mounted on the fingernail surface, and the fingertip force is estimated on the basis of the photodetector outputs. In this paper, we conduct thorough experimental characterization of the sensitivity and efficiency of light transmittance through the fingernail bed to wavelength and optical path length. Results show that the optical parameters for the transmittance of light through the human fingernail bed are optimized when using green light (525 nm) and when the surface mount LED and photodiode are placed as close together as possible.

A novel large-scale OXC architecture and an experimental system that utilizes wavelength path switching and fiber selection

We propose a novel large-scale OXC architecture that utilizes WSSs for dynamic wavelength grouping and 1xn switches for fiber selection. We also develop a network design algorithm that can make the best use of the routing capability of the proposed nodes. Numerical experiments on several topologies show that the architecture attains substantial hardware scale reduction. A prototype demonstrates good transmission performance and confirms the technical feasibility of the proposed OXC architecture.

Experimental demonstration of arrayed optical amplifiers with a shared pump laser for realizing colorless, directionless, contentionless ROADM

We propose arrayed optical amplifiers that share a single pump laser with the aim of realizing full-add/drop colorless, directionless, contentionless ROADM nodes and demonstrate its feasibility in experiments. The experimental results show that the fabricated arrayed optical amplifiers can be made to correspond properly to wavelength path reconfigurations by adjusting a splitting ratio of the variable splitter between the pump laser and eight EDFAs, and cause no significant penalty for 128-Gbit/s PDM-QPSK signal transmission.

Converged Optical Network and Data Center Virtual Infrastructure Planning

This paper presents a detailed study of planning virtual infrastructures (VIs) over a physical infrastructure comprising integrated optical network and data center resources with the aim of enabling sharing of physical resources among several virtual operators and services. Through the planning process, the VI topology and virtual resources are identified and mapped to the physical resources. Our study assumes a practical VI demand model without any in advance global knowledge of the VI requests that are handled sequentially. Through detailed integer linear program modeling, two objective functions - one that minimizes the overall power consumption of the infrastructure and one that minimizes the wavelength utilization - are compared. Both are evaluated for the virtual wavelength path and wavelength path optical network architectures. The first objective results in power consumption savings and the two optical network architectures provide similar performances. However, the trend changes for higher load values, due to the inefficient wavelength utilization that the first objective leads to. Finally, we compare the virtual infrastructures created by the two objectives through online traffic provisioning simulations. The objective minimizing wavelength utilization results in VIs suffering higher request blocking compared to the VIs created by the objective minimizing the overall power consumption.

Experimental Demonstration of Highly Resilient Wavelength-Switched Optical Networks With a Multivendor Interoperable GMPLS Control Plane

The backbone infrastructure for providing carrier-class services, such as a wavelength-switched optical network (WSON), usually involves equipment from multiple vendors. For intelligent path control in the WSON, it is highly desirable to introduce a unified generalized multiprotocol label switching (GMPLS) control plane, which is beneficial for reducing the operational cost and facilitating the dynamic service recovery. However, the interoperability issue of GMPLS-enabled WSON among multiple vendors has not been investigated to date, preventing its wide deployment in an actual operational scenario. Accordingly, in this paper, we experimentally present a highly resilient WSON with a multivendor interoperable GMPLS control plane. We successfully verify the interworking of the GMPLS control plane and wavelength-switching equipment from multiple vendors, and experimentally present dynamic wavelength path control and dynamic lightpath recovery from single-link failures that occur at different times and multiple link failures that occur simultaneously on a multivendor WSON testbed with both control and data planes. To the best of our knowledge, the interoperability trial of GMPLS-controlled WSON is a world first.

Optical Fast Circuit Switching Networks Employing Dynamic Waveband Tunnel

SUMMARY We propose a novel dynamic hierarchical optical path network architecture that achieves efficient optical fast circuit switching. In order to complete wavelength path setup/teardown efficiently, the proposed network adaptively manages waveband paths and bundles of optical paths, which provide virtual mesh connectivity between node pairs for wavelength paths. Numerical experiments show that operational and facility costs are significantly reduced by employing the adaptive virtual waveband connec

Effects of Optical Layer Protection Granularity in Survivable Hierarchical Optical Path Network

This study compares the performances of waveband protection and wavelength path protection in survivable hierarchical optical path networks. Network costs and the number of switching operations necessary are evaluated for different ratios of protected demand. Numerical results demonstrate that waveband protection can drastically decrease the number of switching operations in the case of failure, while both waveband and wavelength path protection effectively reduce the network resources needed compared to single layer optical path networks.

Virtual Fiber Networking and Impact of Optical Path Grooming on Creating Efficient Layer One Services

This paper presents a novel “virtual fiber” network service that exploits wavebands. This service provides virtual direct tunnels that directly convey wavelength paths to connect customer facilities. To improve the resource utilization efficiency of the service, a network design algorithm is developed that can allow intermediate path grooming at limited nodes and can determine the best node location. Numerical experiments demonstrate the effectiveness of the proposed service architecture.

Experimental validation and performance evaluation of OpenFlow-based wavelength path control in transparent optical networks

OpenFlow, as an open-source protocol for network virtualization, is also widely regarded as a promising control plane technique for heterogeneous networks. But the utilization of the OpenFlow protocol to control a wavelength switched optical network has not been investigated. In this paper, for the first time, we experimentally present a proof-of-concept demonstration of OpenFlow-based wavelength path control for lightpath provisioning in transparent optical networks. We propose two different approaches (sequential and delayed approaches) for lightpath setup and two different approaches (active and passive approaches) for lightpath release by using the OpenFlow protocol. The overall feasibility of these approaches is experimentally validated and the network performances are quantitatively evaluated. More importantly, all the proposed methodologies are demonstrated and evaluated on a real transparent optical network testbed with both OpenFlow-based control plane and data plane, which allows their feasibility and effectiveness to be verified, and valuable insights of the proposed solutions to be obtained for deploying into real OpenFlow controlled optical networks.