Novel protection strategies for passive optical networks based on ring and bus topologies

Abstract

AbstractThis paper is focused on passive optical networks (PONs), especially on increasing their network resilience. Because the most critical components in PONs are usually the optical line termination unit (OLT) and optical fibres connecting all network nodes, the main motivation presented within this paper is to improve the resistance of PON against critical failures of OLT and optical fibres between them. Both presented solutions are based on using dual OLT units and the application of asymmetric splitters in order to balance the attenuation and optical signal levels throughout the entire network, while the main innovation consists in the application of ring and bus topologies. Both bus and ring topologies can be formed easily using only passive splitters with optimum splitting ratios; therefore, no active components are necessary. The next advantage is the opportunity of placing both OLT units in physically diverse location, thus increasing the overall network resilience. Moreover, the presented idea with a bus topology offers an additional resistance against the failures of optical fibres connecting the splitters as well. Because the application of asymmetric passive splitters in both solutions is necessary in order to optimize the optical signal levels in the entire network, the mathematical models for calculating of their optimum splitting ratios are included. To verify the functionality of both topologies and their protection mechanisms, complex simulations were performed and are presented in this article as well. Copyright © 2014 John Wiley & Sons, Ltd.