To accommodate an increasing amount of traffic efficiently, elastic optical networks (EON) that can use optical spectrum resources flexibly have been studied. We implement multi-path routing in case we cannot allocate the spectrum with single-path routing. However, multi-path routing requires more guard bands to avoid interference between two adjacent optical paths when compared with single-path routing in EON. A multi-path routing algorithm with traffic grooming technology has been proposed. The researchers assumed that a uniform modulation level was adopted, and so they did not consider the impact of path length on the resources needed. In this paper, we propose a multi-path routing method with traffic grooming considering path lengths. Our proposed method establishes an optical multi-path considering path length, fiber utilization, and the use of traffic grooming. Simulations show we can decrease the call-blocking probability by approximately 24.8% in NSFNET. We also demonstrate the effectiveness of traffic grooming and the improvement in the utilization ratio of optical spectrum resources.

We investigate the problem of switch port allocation in WDM networks that use the hybrid optical-electronic switching node architecture. The objective is to support given traffic demands while minimizing the number of electronic switch ports used, or equivalently minimizing the number of established lightpaths. We first formulate the problem as a mixed integer linear programming (MILP) problem. However, due to the high computational complexity of exact optimization, we develop a simulated annealing (SA) algorithm to get an approximate solution. Results from the SA algorithm demonstrate that, compared to the optical-electrical-optical (O-E-O) node architecture, a WDM network that employs the hybrid switching node architecture requires many fewer lightpaths. We also develop a lightpath assignment heuristic which requires much less computation time than the SA algorithm while maintaining close objective values. The lightpath assignment heuristic is used to investigate the switch port allocation behaviors. Simulation results show that nodes with high degrees or with small average node distances require large numbers of optical switch ports. Moreover, nodes with large amounts of terminate (originated/destined) traffic require large numbers of electronic switch ports. Since the lightpath assignment heuristic requires small computation time, it can be used in the network design process in which a large number of network scenarios must be considered.

We develop a new optical switching fabric with multi-granularity grooming based on our lambda-group model, as well as algorithms that can handle dynamic environments. The proposed fabric based on a new multi-granular grooming scheme presents the distinctive approach of assigning different contiguous groups of granularities to different paths for effective treatment. Results and figures from experiments show that the particular partitioning approach not only is helpful to port reduction significantly, but also improves the SNR of signal and blocking performance for dynamic connection requests.

In this paper we consider algorithms for the logical topology design and traffic grooming problem in WDM networks with router interface constraints as well as optical constraints. The optical constraints include restricted transmission range due to optical impairments as well as limits on the number of available wavelengths. We formulate this problem as an integer linear program which is NP-complete. We then introduce heuristic algorithms which use a graphical modeling tool called the Virtual Neighbor Graph and add lightpaths sequentially. The best performing heuristic uses a so-called Resource Efficiency Factor to determine the order in which paths are provisioned for the traffic demands. By giving priority to demands that can be routed over paths that make efficient use of network resources, it is able to achieve good performance both in terms of weighted hop count and network throughput. For finding optimal multi-hop paths sequentially, we introduce interface constraint shortest path problem and solve it using minimum weight perfect matching.

This paper presents two dynamic multi-layer routing policies for optical IP Networks. Both policies first try to allocate a newly requested electrical path to an existing optical path that directly connects the source and destination nodes. If such a path is not available, the two policies employ different procedures. Policy 1, which has been published already, tries to find available existing optical paths with two or more hops that connect the source and destination nodes. Policy 2, which is proposed in this paper, tries to establish a new one-hop optical path between source and destination nodes. The performances of the two routing policies are evaluated. Simulation results suggest that policy 2 outperforms policy 1 if p is large, where p is the number of packet-switching-capable ports; the reverse is true only if p is small. We observe that p is the key factor in choosing the most appropriate routing policy.