Hybrid amplifier placement in mesh DWDM networks using integer linear programming models

Abstract

Hybrid erbium-doped fiber (EDF)/Raman amplifiers (HFAs) can be utilized to improve the performance of specific fiber spans in dense wavelength division multiplexing (DWDM) networks, aiming to extend the reach and/or increase the capacity of optical channels, thereby reducing the total number of line interfaces required to satisfy a given set of traffic demands. However, HFAs are costlier than simpler EDF amplifiers (EDFAs) since they include Raman pumps in addition to an EDFA. Consequently, it is paramount to place them only at selected fiber spans of the network so as to maximize their impact while keeping their number limited. It has been shown that HFA placement can be a complex task in mesh DWDM networks in view of optical channel diversity, with each fiber span traversed by multiple channels with different source and destination nodes. Building on the approximation that noise adds up incoherently along the transmission path, this paper proposes optimal methods to solve the problem of placing hybrid amplifiers in mesh networks. Particularly, it describes two integer linear programming models, one to determine the minimum number and location of HFAs required to reach a target set of feasible optical channels (i.e., without intermediate 3R regenerators) and another to maximize the number of feasible optical channels given a limited number of HFAs to be deployed. A comprehensive set of network simulations using three reference optical network topologies is reported, providing insight into the effectiveness of the proposed models when compared to existing approaches.