To plan a rapid response and minimize operational costs, passive optical network operators require to automatically detect and identify faults that may occur in the optical distribution network. In this work, we present DSP-Enhanced OTDR, a novel methodology for remote fault analysis based on conventional optical time-domain reflectometry complemented with reference traces and DSP-based techniques. We first obtain the optimal decision thresholds to detect deviations in the noisy OTDR measurement. In order to quantify and characterize the fault, the detection stage is followed by one of estimation where its return loss and insertion loss are determined. We experimentally demonstrate that this approach allows to detect and characterize faults with an accuracy higher than that found in conventional OTDR trace analysis. In our experiments, we achieved detection sensitivities higher than 0.2 dB in a 1:16 split-ratio PON, and higher than 1 dB in a 1:64 split-ratio PON, achieving estimation errors that can be as low as 0.01 dB. We also verified how the optical network terminal's reflectivity can improve the detection capabilities.
We address the issue of false detections in an optical coding-based PON monitoring scheme. An analytical expression for the average number of false detections is derived and the system performance in terms of false detections is evaluated. We show that a feasible, low-cost scheme can monitor a large number of users with less than one false detection per user even in high-density PONs.
We propose a new strategy for designing a logarithmic spiral antenna and the impedance adapter to operate in a frequency range of 1 to 10 GHz. Numerical and experimental results show a decrease in return loss being higher than 20 dB in almost the entire range of operation.
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