Techno-economical evaluation of selected passive optical network architectures

Abstract

Increasing demand for the broadband access is driving the access network evolution towards the fiber based solutions and passive optical networks (PONs) are considered as a promising alternative. Due to the growing demand for reliable service delivery, network reliability issues are becoming very significant and, consequently, an efficient fault management is needed to be considered even in the access part of the network. However, there is a trade off between the cost of protection and the level of service reliability. Since economical aspects are most critical in the access part of the networks, improving reliability performance by duplication of network resources (and capital expenditures CAPEX) can be too expensive. Therefore, some recent works focused on PON protection schemes with reduced CAPEX [1-3]. The future trend will probably migrate towards minimizing the operational expenditures (OPEX) during the access network lifetime. In this paper we present the evolution of protection schemes and compare their reliability performance in relation to the CAPEX and OPEX parameters. We present an OPEX analysis for the fault management in PON and apply the analysis to some selected PON architectures. Furthermore, we compare the total cost, i.e. CAPEX and OPEX, for the considered PON architectures in relation to the reliability performance. To make our analysis more general, we study two typical PON deployment alternatives referred to as collective and dispersive cases. The collective case corresponds to areas with relative dense population of users while the dispersive case is applied to sparsely populated areas. Correspondingly, for the collective case we assume 19.5 km long feeder fiber (FF) and 0.5 km long distribution fibers (DFs) while for the dispersive case 15 km long FF and 5 km long DFs are considered. In our study the lifetime of a PON is assumed to be 20 years. According to our results the contribution of CAPEX in the total cost is higher than the contribution of OPEX in all the studied cases. However, the OPEX still remains a significant part of the total cost and therefore seems to be an important issue for the budget plan of a network operator. It can be noticed that both OPEX and CAPEX may vary between different PON architectures. Therefore, in order to obtain sufficient level of connection availability at lowest possible cost it can be recommended to study both CAPEX and OPEX in relation to the reliability performance before making decision for the network deployment. Our results show that in the areas with relative dense population of users (i.e., in the collective case) it can be sufficient to protect only the shared parts of PON in order to obtain 5 nines (99.999%) connection availability while in the sparsely populated areas (dispersive case) all fiber links should be protected.