Nonintrusive Fiber Monitoring of TDM Optical Networks

• Published in: Journal of lightwave technology 2007-01, Vol.25 (1), p.305-317
• Main Authors: Bert De Mulder, Wei Chen, Bauwelinck, J., Vandewege, J., Xing-Zhi Qiu
• Format: Article
• Language: English
• Subjects: Applied sciences; Backscatter; Bursts; Exact sciences and technology; Excitation; Fault detection; Fibers; Fresnel reflection; Information, signal and communications theory; Laplace transforms; Monitoring; Multiplexing; Networks; o ptical-performance monitoring; Optical communication; Optical fiber communications; Optical fiber networks; Optical fiber testing; Optical fibers; Optical reflection; Optical telecommunications; optical time-domain reflectometry (OTDR); Optical transmitters; optical-fiber communication; passive optical networks (PONs); Performance evaluation; Reflection; Reflectometers; Signal and communications theory; Studies; Systems, networks and services of telecommunications; Telecommunication traffic; Telecommunications; Telecommunications and information theory; Teletraffic; Time division multiplexing; Transmission and modulation (techniques and equipments)
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2006.887184

This paper introduces a new embedded nonintrusive fiber-monitoring technique for time-division-multiplexing optical networks. It allows an optical transmitter to characterize the fiber plant from reflections caused by data bursts transmitted across the network instead of dedicated test signals. The probing is performed with minimal burden on data traffic so that many measurements can be averaged to improve accuracy. The method is very suitable for embedded optical time-domain reflectometers (OTDR), which reuse a network node's optical data transmitter for OTDR excitations and embed a reflectometer inside the fiber endpoint. This paper models the OTDR with Laplace transforms, an approach previously unpursued, after which it is explained how reflections from multiple data bursts with arbitrary width can be converted into one normalized format. This new class of OTDR excites the fiber with a negative step of light instead of the conventional short pulse. The signal-to-noise ratio (SNR) for backscatter and Fresnel reflections caused by the negative step and pulse are compared theoretically. It is shown that negative-step OTDR breaks the tradeoff between excitation pulsewidth and distance resolution, has a natural separation between fiber backscatter and Fresnel reflectors, and improves the SNR of nonreflective events