All-optical Transport Research Articles

Griffin: Programmable Optical DataCenter With SDN Enabled Function Planning and Virtualisation

Optical networking technologies are very attractive for intra-DataCenter (DC) interconnectivity due to their intrinsic high-bandwidth and low-latency characteristics. As the bandwidth demand grows, quantity and size of IT and network infrastructure grows, which puts pressure on power, cost, and space consumption. Therefore, programmable optical networking solutions, which are highly controllable and provide granularity and scalability in services, can greatly enhance operations and resource efficiency for DC interconnects. This paper proposes and reports on a novel function-programmable and application-aware intra-DC technology. The hardware platform uses FPGA implementation of top-of-rack (ToR) switch which supports two main software-defined network functions of a) Ethernet over WDM and b) Ethernet over TDM sub-WDM. Each switch can be programmed to virtually operate as an optical Ethernet or subwavelength transport system. The TDM function further supports a range of additional programmable features in time-slice and frames. The system can be controlled to switch between the functions on-demand and on a hitless manner. This platform with unique flexibility in functions and features is configured to operate with various processing times, throughput, and delays, enables on-demand quality of service (QoS) definition to match diverse cloud application requirements. Optical fast switches enable all-optical transport between the ToRs, further supporting low-latency and resource efficiency. A multistage software-defined controller is built which at the first stage uses application requirements to virtually create function programmable subnetworks by repurposing the data plane functions as well as control plane (algorithms) features. In the second stage, it allows dynamic allocation of resources of the subnetwork for the duration of the application. This platform is characterised to operate with different QoS metrics and evaluated for DC use cases.

All-optical transport and compression of ytterbium atoms into the surface of a solid immersion lens

We present an all-optical method to load 174Yb atoms into a single layer of an optical trap near the surface of a solid immersion lens which improves the numerical aperture of a microscope system. Atoms are transported to a region 20 um below the surface using a system comprised by three optical dipole traps. The "optical accordion" technique is used to create a condensate and compress the atoms to a width of 120 nm and a distance of 1.8 um away from the surface. Moreover, we are able to verify that after compression the condensate behaves as a two-dimensional quantum gas.

Packet–Optical Integration Nodes for Next Generation Transport Networks

The development of a new generation of photonic integrated circuits and the constant progress in integrated electronics (following Moore's law) made the realization of a new type of optical transport node possible, by basing it on the concept of a digital photonic switching layer working in coordination with the packet switching layer under the control of a multi-layer control plane. In this paper such a new type of optical transport node is presented, analyzed and implemented in order to better investigate its potential advantages and weaknesses if compared with the conventional all-optical transport nodes and their level of applicability. The new node concept is based on a “vertical” view of packet-opto networks able to face the challenge of growing network capacity while cutting costs and to allow an efficient combination of digital optical networks and packet-opto integration's benefits. Thanks to the use of optical-electrical-optical conversion technology, the wavelength division multiplexed (WDM) layer is provided with the traffic management flexibility and the engineering simplicity of digital transport systems (significant operational expenditures reduction) and with the network cost savings of large-scale photonic integration (capital expenditures reduction). It combines packet and WDM switching technologies where appropriate, with the ability to offload pass-through traffic from the packet layer to the lowest possible layer, so as to reduce costs and power consumption by eliminating unnecessary packet processing (total cost of ownership reduction). The main building blocks are a new digital optical transport based on an integrated packet-opto node that is scalable, flexible and low cost, and multi-layer control and management based on standard generalized multiprotocol label switching and innovative path computation element (PCE) solutions. Thanks to the flexibility of the digital reconfigurable optical add/drop multiplexer, the PCE is able to handle both layers in a very efficient way by selecting the right granularity for traffic grooming and routing. The feasibility has been assessed by a network prototype composed of four nodes produced by Ericsson Research Lab in Pisa and by a simulation analysis.

Energy-efficiency of all-optical transport through time-driven switching

Decreasing the Internet power consumption is a challenging issue. Optical transport networks employing the wavelength division multiplexing (WDM) technique have been identified as energy efficient solutions to face this issue, considering the expected high increase of Internet traffic. The authors study the energy efficiency of a recently-proposed switching technique for transport networks, the time-driven-switching (TDS), in which time-coordination of network elements is exploited to achieve ‘sub-lambda’ granularity in optical signal switching directly in the optical domain. In order to achieve the fast switching time required by TDS, semi-conductor optical amplifier-based optical switches are exploited. The authors discuss the properties, in terms of the energy efficiency, of a TDS transport network, focusing on the energy requirements of the TDS optical switches. The authors provide a qualitative description of the main contributors to energy consumption in a TDS network. The authors then develop an integer linear programming formulation, in which the physical impairments impact over optical signals is also considered. Power consumption over realistic case study networks for the TDS case is compared to the power consumption for the classical IP over WDM architecture, and in some cases TDS is demonstrated to save more than 55% of power consumption with respect to competing architectures.

Resource discovery in ASON/GMPLS Transport Networks

Automatic resource discovery plays a significant role in next-generation optical networks, where nodes can maintain a large number of input/output ports (fibers, wavelengths, time slots, etc.). This automation avoids long and tedious manual node configurations and minimizes resource misconfiguration probability, which can result in high cost savings for network operators. The generalized multiprotocol label switching (GMPLS) Link Management Protocol (LMP) has been defined to provide such functionalities. However, it requires optical nodes to transmit in-band information, thus requesting link termination on each incoming port. This issue, in transparent optical networks, implies additional hardware, high complexities, or even signal losses. This article proposes and evaluates novel extensions to standard LMP that cope with the discovery of all-optical transport planes. In addition, playing a crucial role in ASON/GMPLS networks, this article also generically covers the automatic discovery of the control plane.

An experimental switching-aware GMPLS-based lightpath provisioning protocol in wavelength-routed networks

In wavelength-routed optical networks, the high-delay introduced by the optical switching fabric for resource reservation increases critically the lightpath setup delay. In order to minimize the setup delay, Generalized Multi-protocol Label Switching (GMPLS) introduced the concept of Suggested Label Object (SL), which allows to start reserving and configuring the hardware with a proposed wavelength from the source node to the destination node. This solution is not optimal in wavelength selective networks (WSN) (i.e., without wavelengths converters). The need of guaranteeing the wavelength continuity constraint for end-to-end optical connections, combined with the lack of global wavelength-based link information (the source node is not aware of which wavelengths are available on each link), makes that the likelihood of establishing a lightpath using the proposed suggested label may be minimum. In this article, we propose an enhancement to the current GMPLS RSVP-TE signaling protocol with offset time-based provisioning that minimizes the lightpath setup, improving the overall network performance in terms of blocking probability and setup delay. Experimental performance evaluation has been carried out in ADRENALINE testbed, a GMPLS-based intelligent all-optical transport network.

An Optical Network Architecture With Distributed Switching Inside Node Clusters Features Improved Loss, Efficiency, and Cost

The novel core network architecture presented in this paper realizes distributed all-optical switching of payload by partitioning the network into a number of geographically limited domains, where two-way reservations are effective. Thus, inside each domain, loss is eliminated, while traffic from many nodes can be aggregated into single bursts, improving efficiency. Clustered nodes contribute contiguous optical slots, which are marshaled into composite optical frames destined for other clusters, under the guidance of a reservation-based control protocol. The lossless aggregation of traffic from several core nodes allows the use of cost-effective bufferless all-optical transport among the domains with electrical buffers employed at the periphery of the system. The end result is a triple improvement in loss probabilities, efficiency, and cost. This is achieved by exploiting three features of the architecture: the distributed switching functionality (as in early LANs when centralized switching was expensive), localized reservations (avoiding the intolerable delays of end-to-end reservations), and a reduced number of source-destination pairs (by means of node clustering into reservation domains)

Automatic transport plane resource discovery mechanisms for ASON/GMPLS ring networks

In this letter, we propose two novel mechanisms which enable GMPLS LMP to cope with the automatic discovery of all-optical transport planes. The feasibility of our contributions and their performances are assessed by simulations as well as experimental results over the ASON/GMPLS CARISMA field-trial.

Routing Framework for All-Optical DWDM Metro and Long-Haul Transport Networks With Sparse Wavelength Conversion Capabilities

In this paper, we propose a novel routing framework for all-optical dense wavelength-division-multiplexing transport networks with sparse wavelength conversion capabilities. The routing framework includes an integer linear programming formulation to handle the static lightpath establishment problem and a novel open shortest path first protocol extension that advertises the availability of wavelength usage and wavelength conversion resources. Our routing framework addresses the limitations of the extensions presented in the literature because it also includes: 1) an efficient flooding protocol that is suitable for the dynamic nature of these networks and 2) an efficient route and wavelength computation engine that minimizes connection costs without hindering the blocking probability.

Field Demonstration of In-Line All-Optical Wavelength Conversion in a WDM Dispersion Managed 40-Gbit/s Link

The development of wavelength-division multiplexing (WDM) all-optical transport networks is an interesting solution to increase the capacity of long-haul transmission systems and to solve the route-exhaust problems of metropolitan networks, driving down the cost of that traffic. Routing can be achieved using a transparent device able to select and interchange wavelengths, such as an all-optical wavelength converter. In this paper, an optical transport network over an embedded link located between Rome and Pomezia in Italy is emulated. The transmission has been realized along a WDM, 5/spl times/100 km long, dispersion managed link at 40 Gb/s. The in-line rerouting process has been controlled by means of an all-optical wavelength converter realized with a periodically poled lithium niobate waveguide. Moreover, a polarization-independent scheme for the converter has been exploited to allow the in-line signal processing. This scheme is based on the counterpropagation of TE and TM signal components along the same guide and results extremely compact. In this paper it is demonstrated that wavelength conversion and rerouting add no penalty with respect to the simple transmission along the embedded cable. This result seems to be another step toward the feasibility of true all-optical networks.

QoS Recovery Schemes Based on Differentiated MPLS Services in All-Optical Transport Next Generation Internet

The Internet is evolving from best-effort service toward an integrated or differentiated service framework with quality-of-service (QoS) assurances that are required for new multimedia service applications. Given this increasing demand for high bandwidth Internet with QoS assurances in the coming years, an IP/MPLS-based control plane combined with a wavelength-routed dense wavelength division multiplexing (DWDM) optical network is seen as a very promising approach for the realization of future re-configurable transport networks. Fault and attack survivability issues concerning physical security in a DWDM all-optical transport network (AOTN) require a new approach taking into consideration AOTN physical characteristics. Furthermore, unlike in electronic networks that regenerate signals at every node, attack detection and isolation schemes may not have access to the overhead bits used to transport supervisory information between regenerators or switching sites to perform their functions. This paper presents an analysis of attack and protection problems in an AOTN. Considering this, we propose a framework for QoS guarantees based on the differentiated MPLS service (DMS) model and QoS recovery schemes against QoS degradation caused by devices failures or attack-induced faults in an AOTN. We also suggest how to integrate our attack management model into the NIST’s simulator—modeling, evaluation and research of lightwave networks (MERLiN).

MPLS Recovery Mechanisms for IP-over-WDM Networks

Due to the fast increase of Internet traffic and the enormous bandwidth potential of all-optical transport networks based on wavelength division multiplexing, an IP-over-WDM network scenario is likely to be widespread in future communication networks. At the same time, IP networks are becoming more and more mission-critical. Hence, it is of paramount importance for IP-over-WDM networks to be able to recover quickly from frequently occurring network failures. This paper explains how multi-protocol label switching (both electrical and optical) recovery mechanisms can be important to reach that goal. Moreover, a novel MPLS recovery mechanism called fast topology-driven constrained-based rerouting is presented. Different MPLS recovery mechanisms are compared to each other. Special attention hereby goes to the additional capacity that is required to recover from frequently occurring failures.

A novel all-optical transport network with time-shared wavelength channels

High-speed and high-capacity transport networks are necessary for providing future broadband services and multimedia applications. Optical networks, such as wavelength-routed networks and optical switching networks, are the most popular solutions. However, the limited electronic switching capability constrains the scalability of the multihop wavelength routed networks, while the difficulty and complexity of implementing efficient optical buffers and optical contention resolution schemes constrains the development of optical switching networks. This paper proposes a new architecture for the optical transport networks based on time-wavelength-space routers (TWSRs). The TWSR is equipped without optical buffers and optical contention resolution devices. A connection is established by constructing a time-slot based lightpath (ts-lightpath) between source TWSR and destination TWSR. The paper also proposes a heuristic algorithm for the problem of establishing the set of efficient ts-lightpaths for a given set of connection requests. The effectiveness of the proposed network architecture with the heuristic algorithm is demonstrated by simulation.

Minimum cost wavelength-path routing and wavelength allocation using a genetic-algorithm/heuristic hybrid approach

Minimum cost wavelength-path routing and wavelength allocation of multiwavelength all-optical transport networks using a genetic-algorithm (GA)/heuristic hybrid approach is described. A cost model is adopted which incorporates a dependency on link wavelength requirements. The hybrid algorithm developed uses an object-oriented representation of networks, and incorporates four operators: path mutation, single-point crossover, reroute and shift-out. In addition, an operator-probability adaptation mechanism is employed to improve operator productivity. Experimental results from seven fifteen-node test networks, obtained using a tool for optical network optimisation, modelling and design (NOMaD), suggest the GA/heuristic hybrid approach provides superior results compared to three recent wavelength-allocation heuristics, except when the network cost depends most heavily on wavelength requirement.

All-optical four-fiber bidirectional line-switched ring

An all-optical four-fiber bidirectional line-switched ring (O-4F/BLSR) architecture is proposed. This new physical layer networking protocol uses wavelengths as tributaries and an optical supervisory channel to carry overhead information. Optical channels can be added and dropped from the ring, and virtual wavelength paths can be provisioned. Both node and link failures of a network can be protected through a two layer protection scheme. Protection switching within the optical multiplex section layer (OMS) restores failure caused by loss of optical continuity in a way similar to the SONET 4F/BLSR line switching. Protection switching within the optical channel layer restores single channel failure using 1:N protection. Test results show that the O-4F/BLSR can restore traffic in less than 50 ms. A self-healing, bandwidth efficient, and scalable all-optical transport network evolving from this O-4F/BLSR architecture is possible.

A novel optical-path supervisory scheme for optical cross connects in all-optical transport networks

We propose and demonstrate a novel and effective supervisory scheme to monitor the optical-path routing at the optical cross connects in all-optical transport networks. Any error in optical-path routing due to failure in the cross connect can be detected without tapping off the power at the data wavelengths, and no dedicated monitoring light source is required. The scheme supports in-service surveillance. It can facilitate the network management in the optical layer of all-optical and reconfigurable transport networks.

Wavelength-matching scheme for wavelength gratingrouters in all-optical transport networks

The authors propose and demonstrate a new wavelength-matching scheme for wavelength grating routers in all-optical transport networks. The wavelength assignment of the data channels and the transmission peaks of the wavelength grating routers can be matched automatically and continuously. The scheme uses the unutilised ASE spectra of the EDFA as the source and a temperature-compensated fibre Bragg grating as the matching indicator. It is also insensitive to dynamic ASE power variations arising from channel add-drop.

Minimum network wavelength requirementdesign using a genetic-algorithm/heuristic hybrid

Minimum network wavelength requirement design of multi-wavelength all-optical transport networks using a genetic-algorithm (GA)/heuristic hybrid approach is described. Improved performance (over a GA alone) and improved results (over recent heuristics) are obtained using a tool for optical network optimisation, modelling and design (NOMaD).

Impact of transmission performance on path routing in all-optical transport networks

The impact of transmission related issues on the routing strategies for transparent all-optical wavelength division multiplexed (WDM) transport networks is analyzed in this paper. Three different categories of routing algorithms are analyzed: algorithms based on the wavelength path (WP) strategy, based on the virtual wavelength path (VWP) strategy and requiring only a limited number of wavelength converters in the network partial virtual wavelength path (PVWP). It results that the PVWP allows a saving in network devices with respect to the WP similar those permitted by the VWP also attaining transmission performances near those attained by the WP that are quite better that those attained by the VWP.

A wideband all-optical WDM network

We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications.