Experimental Validation of Periodic Codes for PON Monitoring

In this paper we investigate both experimentally and via simulation the monitoring of fiber link quality in a PON using optical coding technology. We use a new, simple and cost-effective coding scheme well adapted to the monitoring application, namely periodic coding. We discuss design issues for periodic coding and the optimal detection criteria. We develop a reduced complexity maximum-likelihood sequence estimation (RC-MLSE) algorithm for monitoring. We conduct experiments to validate our detection algorithm using four periodic encoders that we designed and fabricated. These encoders were placed at roughly equal distances (within a meter) to represent a partial return from a very high density (geographically) PON. The measured data were fed into our detection algorithm and the exact location of each subscriber was correctly identified. Using the experimental data for the encoder's impulse responses, we completed Monte-Carlo simulations for more realistic PON geographical distributions with randomly located customers. Error-free detection is achieved. We also highlight the importance of averaging to remedy the power/loss budget limitations in our monitoring system to support higher network sizes.