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14 February 2002 Distributed microbend optical sensor with directional swelling and optimal bending frequency
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Proceedings Volume 4578, Fiber Optic Sensor Technology and Applications 2001; (2002)
Event: Environmental and Industrial Sensing, 2001, Boston, MA, United States
This work describes the performance of a new optical distributed sensor. This new sensor is capable of detecting and locating liquid hydrocarbon leakage on long pipelines. It is an improvement over the current fiber bending distributed sensors that use a polymeric filament that interacts with an optical fiber by means of a helicoidal wire. When a liquid or gas compatible with the polymeric filament within this type of sensor comes in contact with it, the liquid is absorbed and causes the swelling of the filament and the concomitant compression of the optical fiber against the helicoidal wire. This phenomena cause the fiber to bend and generate an increase on the optical attenuation signal that travels through the fiber. The signal attenuation permits the detection of a specific liquid presence in the vicinity of the sensor and the reflection of the same signal allows to pinpoint the location of this event. The new sensor has the following advantages over similar devices: a) the swelling of the polymeric filament is conducted in a preferential direction permitting to concentrate the osmotic pressure towards the optical fiber. This improves significantly the response speed of the sensor. b) The fiber is placed within a capillary channel located eccentrically in the polymer filament; therefore, no additional protection is needed to prevent damage to the fiber. Of even greater importance, the signal attenuation provoked by stress and deformations due to direct contact of the fiber with the helicoidal wire is avoided. And finally, c) an optimal bending period that take in count the polymer nature to improve the sensor response was found and employed. An experimental prototype of this sensor was fabricated using a multimode optical fiber attached to a polybutadiene filament. The experimental results confirm the benefits of this new design.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Antonio Carrillo, Armando Tomas Rosas Molina, and Alfredo Marquez Lucero "Distributed microbend optical sensor with directional swelling and optimal bending frequency", Proc. SPIE 4578, Fiber Optic Sensor Technology and Applications 2001, (14 February 2002);

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