Proceedings PaperForward-Scatter Distributed Optical-Fibre Sensing Using Non-Linear Interactions
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The advantages offered by optical-fibre sensors are well known. Distributed optical-fibre sensors utilise the one-dimensional nature of an optical fibre to offer the additional advantage of the determination of the distribution of the measurand along the path of the fibre, with a spatial resolution 0.1-10m, depending on the system and the application. Most distributed optical-fibre measurement systems which have been studied hitherto have relied on time-domain backscatter (OTDR) techniques. In these, the spatial information is obtained via time resolution of the light backscattered from a pulse propagating in the fibre. These techniques suffer from the fact that backscattered light levels are low; thus signal detection and signal processing become problematic. An alternative approach is to extract the information from forward-scattered light by allowing counter-propagating light waves to interact non-linearly in the fibre. Detected signal levels then become some three orders of magnitude higher. The paper investigates this alternative approach.