Multi-granularity Optical Switching Research Articles

Dynamic weight routing and optical-code algorithm based on SDN

Optical transport networks are evolving towards multi-granularity switching and software management but require that the architecture of the existing control plane be adapted to multi-service and network management requirements. So a dynamic weighting algorithm based on optical code resources and the matching degree between service request and channel is proposed for a multi-granularity optical switching system. In which, Software Defined Networking (SDN) controller collects network resource information in real time, dynamically changes the weight of each path and use it for path calculation, provides a more matched path on the premise of load balancing, and combines its channel matching weights for resource allocation. The simulation results show that the multi-granularity switching system with the proposed algorithm can reduce the generation of optical code fragments and improve resource utilization effectively. In the end of the paper, the optical code routing algorithms are simulated and implemented, and their performances are compared and analyzed. The simulation results show that the blocking rate of the matching algorithm on the NSFNET network is reduced by an average of 4% compared with the traditional algorithm, and the resource utilization of the optical code is improved by 9%.

Research on optical code assignment algorithm based on PCE domain

Abstract In the multi-granularity optical switching system with optical-code granularity, the wavelength and optical code resource reservation table is established in the PCE domain according to the PCEP common standard, which effectively solves the problem of reserved optical-code conflict in the resource reservation request process, and reasonably allocates utilize the optical code resources in the optical network. At the same time, based on the principle of multi-granularity optical code switching, the exchange path computation algorithm of multi-granularity switching system refined to optical-code packet granularity is studied, and a new routing and optical-code assignment (ROCA) scheme is given. An optical-code fragment minimization allocation algorithm is proposed, which adaptively routes resources according to service segmentation and optical-code polling, rationally utilizes optical-code resources in wavelengths, and effectively reducing optical-code fragments and improving used wavelengths. Furthermore, the blocking rate of the network is reduced. Compared with the First-Fit algorithm, this algorithm reduces the blocking rate of the network and improves the throughput of the network.

Experimental demonstration of multigranularity switching between optical DFT-spread-OFDM and Nyquist superchannel

We experimentally investigate multigranularity optical subband switching functionality between two superchannels with slight error vector magnitude penalty. One is 4×39 Gb/s polarization-division-multiplexed (PDM) quadrature phase shift keying discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-spread-OFDM) superchannel with 12.5 GHz band spacing. The other is 8×29 Gb/s PDM-16-quadrature amplitude modulation Nyquist pulse shaping superchannel with 6.25 GHz band spacing. To the best of our knowledge, this is the first time that optical switching functionality for individual band between different superchannels with multigranularity is realized.

Field Trial of an OpenFlow-Based Unified Control Plane for Multilayer Multigranularity Optical Switching Networks

Software defined networking and OpenFlow, which allow operators to control the network using software running on a network operating system within an external controller, provide the maximum flexibility for the operator to control a network, and match the carrier's preferences given its centralized architecture, simplicity, and manageability. In this paper, we report a field trial of an OpenFlow-based unified control plane (UCP) for multilayer multigranularity optical switching networks, verifying its overall feasibility and efficiency, and quantitatively evaluating the latencies for end-to-end path creation and restoration. To the best of our knowledge, the field trial of an OpenFlow-based UCP for optical networks is a world first.

Multi-Granular Optical Switching: A Classified Overview for the Past and Future

The wavelength routed network (WRN) accommodates traffic demands by establishing lightpaths along the corresponding routing paths. The wavelength of each lightpath is switched individually by traditional wavelength optical cross-connects (T-OXCs) to transit the traffic. Due to the traffic explosion and the resulted growth in wavelength number, WRNs face a challenge of the increase in node-size (i.e., the port number of a T-OXC) as well as the associated cost and control complexity. As an alternative solution, waveband switching (WBS) is introduced to group multiple wavelengths together as a band or fiber. Whenever possible, the group of wavelengths requires just a single port at a multi-granular optical cross-connect (MG-OXC). One fundamental problem in WBS networks is the routing and wavelength assignment (RWA). With the major goal of minimizing the port numbers in WBS networks, the optimal RWA problem was shown to be NP-Hard. In the literature, various Integer Linear Programming models are proposed to optimally solve a small-size RWA problem, and many heuristic algorithms are proposed to provide a practical solution for the large-scale RWA problem in WBS networks. In this work, we comprehensively review literature studies on waveband switching networks. The topics covered include architecture, RWA problem solving strategies, and future challenges of wavelength conversion, protection, and lightpath rerouting in WBS networks. We aim at presenting a classified view of WBS networks, based on various aspects including the traffic pattern, node and network architecture, grouping policy, and the band configurations. We investigate factors that affect the goal of port reduction and blocking minimization in WBS networks. In addition, we explore several unique features of waveband switching in protection, wavelength conversion and rerouting, along which we point out multiple open challenges in WBS networks that deserve further studies.

Performance analysis and dimensioning of multi-granular optical networks

Recent years have demonstrated the limited scalability of electronic switching to realize transport networks. In response, all-optical switching has been identified as a candidate solution to enable high-capacity networking in the future. One of the fundamental challenges is to efficiently support a wide range of traffic patterns, and thus emerges the need for equipment that is both practical and economical to construct and deploy. We have previously proposed the use of multi-granular optical cross-connects (MG-OXC), which support switching on both the wavelength and sub-wavelength level. To this end, the MG-OXCs are equipped with cheap, highly scalable slow switching fabrics, as well as a small number of expensive fast switching ports. The goal of this work is two-fold: first to demonstrate that a small number of fast switching ports suffices to support a wide range of traffic requirements, and second that multi-granular optical switching can offer cost-benefits on a network-wide scale. The first objective is studied through simulation analysis of a single switching node, and results indicate that a limited number of fast switching ports can significantly improve burst blocking performance over slow only switches. Furthermore, under certain circumstances, the MG-OXC can even approach the performance of a fast only switch design. Secondly, we introduce an Integer Linear Programming model for the total network installation cost, and our evaluation indicates that multi-granular optical switching can be a cost-effective solution on the network level, in comparison to slow only or fast only approaches. Furthermore, we can achieve reduced costs of individual OXC nodes, which allows us to minimize scalability problems corresponding to emerging fast switching fabrics.

Optimizing Fiber Topologies for WDM Optical Networks Based on Multi-Granularity Optical Switching Technology

For the quality of service (QoS) and fairness considerations, the hop counts of various lightpaths in a wavelength division multiplexing (WDM) optical network should be short and compact. The development of multi-granularity optical switching technology has made it possible to construct various fiber topologies over a fixed physical topology. This paper describes a fiber topology design (FTD) problem, which minimizes the maximum number of required fibers in the physical links for a maximum lightpath hop count in the fiber topology. After the formular description for the FTD problem, a method was given to obtain the lower bound on the maximum number of required fibers. For large or moderate scale networks, three heuristic algorithms are given to efficiently solve the FTD problem. This study gives a new way to optimize the resource configuration performance in WDM optical networks at the topology level and proves its effectiveness via both analyses and numerical experiments.

Smart design of multigranular optical switching fabric with traffic grooming

We introduce an intelligent optical cross connect OXC structure based on our lambda-group model, as well as a dynamic algorithm of configuration helpful to compli- cated optical traffic grooming, which presents a distinctive approach of dividing granularities into specific tunnels for ef- fective treatment. Results and figures from experiments show that the particular channel partition not only is helpful to port reduction significantly, but also improves the channel and blocking performance for dynamic connection requests. © 2006 Society of Photo-Optical Instrumentation Engineers.

Multigranular integrated services optical network

Feature Issue on Waveband Switching, Routing, and GroomingBased on all-optical switches without requiring fiber delay lines and optical-electrical-optical interfaces, the multigranular optical switching (MGOS) network integrates three transport services via unified core control to efficiently support bursty and stream traffic of subwavelength to multiwavelength bandwidth. Adaptive robust optical burst switching (AR-OBS) aggregates subwavelength burst traffic into asynchronous light-rate bursts, transported via slotted-time light paths established by fast two-way reservation with robust blocking recovery control. Multiwavelength optical switching (MW-OS) decomposes multiwavelength stream traffic into a group of timing-related light-rate streams, transported via a light-path group to meet end-to-end delay-variation requirements. Optical circuit switching (OCS) simply converts wavelength stream traffic from an electrical-rate into a light-rate stream. The MGOS network employs decoupled routing, wavelength, and time-slot assignment (RWTA) and novel group routing and wavelength assignment (GRWA) to select slotted-time light paths and light-path groups, respectively. The selected resources are reserved by the unified multigranular robust fast optical reservation protocol (MG-RFORP). Simulation results show that elastic traffic is efficiently supported via AR-OBS in terms of loss rate and wavelength utilization, while connection-oriented wavelength traffic is efficiently supported via wavelength-routed OCS in terms of connection blocking and wavelength utilization. The GRWA-tuning result for MW-OS is also shown.