Upgrading Links with Ultra-Low Loss Fibers in a Survivable Elastic Optical Network

Abstract

The lifespan of a fiber cable is generally limited, typically 20 ~ 25 years. It is foreseen that there will be a large number of fiber cables expired and requiring to be upgraded in the near future since many fiber cables were deployed in the last century. Ultra-low loss (ULL) fibers promise enhanced transmission performance, which has been considered as an important candidate for replacing old standard single mode fibers (SSMFs). However, upgrading all the fibers in a network in one go will not only be prohibitively costly but will also be difficult to undertake because of the usually limited labor resources. Network operators are expected to upgrade only a partial set of network links at a time, in order to change over progressively to ULL fibers. Thus, how to upgrade network links with ULL fibers efficiently is important to investigate. In this paper, we address this problem for a survivable elastic optical network (EON). We consider three different fiber upgrading strategies – random, physical length based (PL), and least cost based (LC) strategies. We consider the routing, modulation format, and spectrum assignment (RMSA) problem for an EON with partially upgraded fiber links, aiming to minimize the number of frequency slots (FSs) used. The RMSA problem is formulated as a mixed integer linear programming (MILP) model. And also for handling large-size networks, a spectrum window plane (SWP) based heuristic algorithm is developed to incorporate the steps of ULL fiber upgradation and RMSA. Studies show that the number of FSs used decreases when the total link distance replaced increases, and a ULL fiber with a 0.168-dB/km attenuation coefficient is sufficient to achieve good performance and further reducing the coefficient would not bring much performance improvement.