φ-OTDR-based Distributed Optical Fiber Sensing System

Distributed optic-fiber sensing (DOFS) system is a kind of distributed sensing system using optic-fiber as the sensing medium, and carries on real-time remote security monitoring of the target within it. The distributed sensor described in this paper utilizes a phase-sensitive OTDR (φ?OTDR) system designed to enhance coherent effects. Phase sensitivity results from interference of the light cackscattered from different parts of the fiber, which arrive simultanmeously at the photodetector. As a practical matter, theφ?OTDR can detect perturbations much too small to be perceived with a conventional OTDR system.φ?OTDR distributed optic-fiber sensing system not only has the features of electromagnetic immunity, anti-eroding and sensitivity, but also takes advantages of hardly being revealed, precise alarm locating, easily data prcessing and so on as a novel alarm monitoring system. Such a distributed sensing system is anticipated to be used widely in safety monitoring of military bases, national boarders, nuclear facilities, electrical power generation stations, jails, et al.The author has done a lot of pioneering theoretical and experimental work about this challenging and innovativeφ?OTDR distributed optic-fiber sensing system. Detailed work is listed below:(1) The distributed optical fiber sensing system feasibility solution was analysed and present situation of distributed optic-fiber fiber system was also studied. It showed that the distributed optical fiber system based onφ?OTDR technology had significant economic value and social value.(2) Starting with the theory of OTDR, the theory ofφ?OTDR distributed optic-fiber sensing system was analysed.(3) Aφ?OTDR distributed optic-fiber sensing system based on a fiber laser with high power and narrow linewidth was proposed.(4) Using the EOM, the laboratory simulation experimental testing was conducted. By processing the returned signal properly, the system can locate the intrusion point, within a distance range of 14km, with the best spatial resolution of ~50m reported to date. Then, the field tests based on this solution were conducted too.(5) Using the AOM, the laboratory simulation experimental testing was conducted. The system can locate the intrusion point, with a spatial resolution of ~50m, within the longest distance range of 25km reported to date.(6) The relationship of stimulated Brillouin scattering and the performance of the system was analysed.(7) An OTDR distributed optic-fiber sensing system based on sub-carrier method was proposed.(8) Intrusion alarm system software was designed and developed for achieving alarm and partly judgment function in software form based on LabVIWEW.