Measurement Based Reconfigurations in Optical Ring Metro Networks

Single-hop wavelength division multiplexing (WDM) optical ring networks operating in packet mode are one of themost promising architectures for the design of innovative metropolitan network (metro) architectures. They permit a cost-effective design, with a good combination of optical and electronic technologies, while supporting features like restoration and reconfiguration that are essential in any metro scenario. In this article, we address the tunability requirements that lead to an effective resource usage and permit reconfiguration in optical WDM metros.We introduce reconfiguration algorithms that, on the basis of traffic measurements, adapt the network configuration to traffic demands to optimize performance. Using a specific network architecture as a reference case, the paper aims at the broader goal of showing which are the advantages fostered by innovative network designs exploiting the features of optical technologies

Multi-Channel Deficit Round-Robin Scheduling for Hybrid TDM/WDM Optical Networks

In this paper we propose and investigate the performance of a multi-channel scheduling algorithm based on the well-known deficit round-robin (DRR), which we call multi-channel DRR (MCDRR). We extend the original DRR to the case of multiple channels with tunable transmitters and fixed receivers to provide efficient fair queueing in hybrid time division multiplexing (TDM)/wavelength division multiplexing (WDM) optical networks. We take into account the availability of channels and tunable transmitters in extending the DRR and allow the overlap of `rounds' in scheduling to efficiently utilize channels and tunable transmitters. Simulation results show that the proposed MCDRR can provide nearly perfect fairness with ill-behaved flows for different sets of conditions for inter-frame times and frame sizes in hybrid TDM/WDM optical networks with tunable transmitters and fixed receivers

New trends on Optical Access Networks: DBAs for 10G EPON and Long-Reach PON

The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include mechanisms for the integration of different technologies. New optical access technologies trends are: WDM, 10 Gb/s, and longer reach/higher splits. It is also important to take into account the evolution of the installed legacy PONs to the next generation optical access networks. The present paper goes through such topics, focusing on the research being carried out to develop dynamic bandwidth algorithms for the 10 Gb/s new EPON standard (IEEE 802.3av). We summarize results and point out issues that will require further investigation.Postprint (published version

Scheduled virtual topology design under periodic traffic in transparent optical networks

This paper investigates offline planning and scheduling in transparent optical networks for a given periodic traffic demand. The main objective is to minimize the number of transceivers needed which make up for the main network cost. We call this problem ldquoScheduled Virtual Topology Designrdquo and consider two variants: non-reconfigurable and reconfigurable equipment. We formulate both problems as exact MILPs (Mixed Integer Linear Programs). Due to their high complexity, we propose a more scalable tabu search heuristic approach, in conjunction with smaller MILP formulations for the associated subproblems. The main motivation of our research efforts is to assess the benefits of using reconfigurable equipment, realized as a reduction in the number of required transceivers. Our results show that the achieved reductions are not very significant, except for cases with large network loads and high traffic variability.The work described in this paper was carried out with the support of the BONE-project ("Building the Future Optical Network in Europe”), a Network of Excellence funded by the European Commission through the 7th ICTFramework Programme, support of the MEC Spanish project TEC2007- 67966-01/TCM CONPARTE-1 and developed in the framework of "Programa de Ayudas a Grupos de Excelencia de la Región de Murcia, de la Fundación Séneca (Plan Regional de Ciencia y Tecnología 2007/2010).

A Fast Scheduling Algorithm for WDM Optical Networks

Wavelength Division Multiplexing (WDM) is emerging as the most promising approach to exploit the huge bandwidth of optical fibre. This approach divides the optical spectrum into many different channels where each channel corresponds to a different wavelength. Single-hop WDM networks are attractive in local area environment where all the nodes can be connected to a single broadcast facility. In a single-hop WDM broadcast network, the transmitter must know when to transmit a packet and at which wavelength, while the receiver must know when to tune to the appropriate wavelength to receive the packet. This process requires some form of coordination. Many researches have focused on the scheduling algorithms that perform this kind of coordination. This thesis proposes a scheduling algorithm for the WDM broadcast networks. The algorithm employs a theory in graph, known as edge colouring of bipartite multigraph to produce the transmission schedule, which is free from collision due to the nature of the edge colouring. An optimal edge colouring of bipartite multi graph can be found in O(M log2 N) time, where M is number of packets selected for scheduling, and N is the number of the nodes. This time complexity can be improved to O(log3 N) by parallel processing using O(M) processors. Two variations of implementation of the scheduling algorithm have been proposed, namely the Variable Frame Size (VFS) and Limited Frame Size (LFS) schemes. These schemes use different criteria to select packets from the nodes for scheduling. The VFS scheme is simple, but supports only best effort transmissions. The LFS scheme ensures the frame size of the transmission schedule is bounded, thus enabling it to support bandwidth guarantee to the nodes up to a node's fair share of the network capacity. The LFS scheme is capable of supporting constant bit rate and unspecified bit rate service categories, analogous to the Asynchronous Transfer Mode (ATM) services. The results show that the LFS scheme performs better than the VFS scheme in terms of channel utilisation, packet loss probability and network throughput for all the simulated traffic patterns, especially at heavy loads. Besides, the LFS scheme respects any level of bandwidth guarantee, while the unused bandwidth can be used for best effort transmissions. The results also show that the VFS and LFS schemes are future-proof as they are able to capitalise on the increase in the number of wavelength channels

Dynamic Optical Networks for Data Centres and Media Production

This thesis explores all-optical networks for data centres, with a particular focus on network designs for live media production. A design for an all-optical data centre network is presented, with experimental verification of the feasibility of the network data plane. The design uses fast tunable (< 200 ns) lasers and coherent receivers across a passive optical star coupler core, forming a network capable of reaching over 1000 nodes. Experimental transmission of 25 Gb/s data across the network core, with combined wavelength switching and time division multiplexing (WS-TDM), is demonstrated. Enhancements to laser tuning time via current pre-emphasis are discussed, including experimental demonstration of fast wavelength switching (< 35 ns) of a single laser between all combinations of 96 wavelengths spaced at 50 GHz over a range wider than the optical C-band. Methods of increasing the overall network throughput by using a higher complexity modulation format are also described, along with designs for line codes to enable pulse amplitude modulation across the WS-TDM network core. The construction of an optical star coupler network core is investigated, by evaluating methods of constructing large star couplers from smaller optical coupler components. By using optical circuit switches to rearrange star coupler connectivity, the network can be partitioned, creating independent reserves of bandwidth and resulting in increased overall network throughput. Several topologies for constructing a star from optical couplers are compared, and algorithms for optimum construction methods are presented. All of the designs target strict criteria for the flexible and dynamic creation of multicast groups, which will enable future live media production workflows in data centres. The data throughput performance of the network designs is simulated under synthetic and practical media production traffic scenarios, showing improved throughput when reconfigurable star couplers are used compared to a single large star. An energy consumption evaluation shows reduced network power consumption compared to incumbent and other proposed data centre network technologies