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.
In this work, we propose a novel method for continuous real-time measurement of the dynamics of the nonlinear refractive index n 2 . This is particularly important for characterizing phenomena or materials (such as biological tissues, gases and other compounds) whose nonlinear behavior or structure varies rapidly with time. The proposed method ingeniously employs two powerful tools: the spectral broadening induced by self-phase modulation and the real-time spectral analysis using the dispersive Fourier transformation. The feasibility of the technique is experimentally demonstrated, achieving high-speed measurements at rates of several MHz. Third-order nonlinear interaction between light and materials (known as theKerr effect) is a major research field [1]. Measurements of the nonlinear refractive index n 2 are of utmost interest for many applications, including the study of the nonlinear properties of novel materials [2], biological tissues [3]-[4], liquids [5] and gases [6]. Moreover, nonlinear waveguides such as highly nonlinear optical fibers and integrated devices are gaining much research interest as photonic sensors [7]-[8].The most extended method for measuring n 2 of thin samples is the Z-scan method [9], which is based on the selffocusing effect of a probe beam and the power measurement behind an aperture versus the sample position. A temporal analog of the Z-scan substitutes the translation stage with a tunable dispersive line [10], allowing to characterize both bulk materials and waveguides. In order to obtain the nonlinear coefficient of waveguides such as optical fibers, several techniques based on self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) have been developed, which employ interferometric methods [11]-[12] that require time-consuming power scans and are sensitive to polarization effects. An approach for measuring the nonlinearity of very short fibers based on the acousto-optic interaction effect was recently demonstrated [13]. Techniques based on measuring the SPM-broadened spectrum are widely used to characterize the nonlinearity of bulk samples [2] and waveguides [14], [15], but they rely on slow optical spectrum analyzers or tunable filters, and thus, they are not suitable for high-speed measurements. All of the above-mentioned methods require performing
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.