Protection for an Immediate Split Structure of Tree-Based EPON Architecture-Ideal Condition Analysis

Abstract

Problem statement: Ethernet Passive Optical Network (EPON) was proposed to overcome the bandwidth bottleneck at the Access Networks due to its simplicity, cost effective and wide spread deployment. A failure in access networks can cause serious problems, because access network transmit aggregated high speed traffic from hundreds of subscribers. Protection and restoration mechanisms have been applied in backbone networks, but access networks are not considered significantly in the scope of survivability. Approach: In this study, we proposed a cost effective protection scheme for a novel tree-based EPON architecture. Immediate Split Structure (ISS) means the signal was totally split after pass through the first optical splitter. This was the second proposal method after first suggestion using Optical Cross Add and Drop Multiplexer (OXADM) as a restoration switch. In this study we used only 2 × 2 and 2 × 1 optical switches combination to divert the traffic to the alternative path. Three faulty conditions were considered in this research and OptiSystem, Inc software was used to prove the solution feasibility. Results: The Bit Error Rate (BER) performances were measured by a 1.25 Gb sec^-1 Non-Return-to-Zero (NRZ) pseudo random binary sequence (PRBS) with a pattern length of 2^31-1 for the downstream traffic between the OLT and 8 ONUs. Our results were obtained by observing bit error rates, eye diagrams and optical power levels in ideal condition. Conclusion: The survivability of EPON is necessary to provide seamless services and ensure network reliability. Single failure in the line connected will activate dedicated protection while shared protection was activated when both fiber (working and standby fiber) are breakdown. We analyzed the system in ideal condition to prove the system feasibility.