New distributed optical sensor for detection and localization of liquid hydrocarbons: Part II: Optimization of the elastomer performance

This paper reports the second part of a work that introduces and describes the testing of a new optical distributed sensor. This new sensor is capable of detecting and locating liquid hydrocarbon leaks on long pipelines. In the first part of this work a number of advantages of this new design were presented. The present part deals specifically with the influence of elastomer preparation on the performance of this sensor, and in a more general way, with the performance of any distributed optical sensor based on optical fiber bending by a swelled elastomer. The results show that the optimal sensor response is obtained when the osmotic pressure developed by the elastomer due to hydrocarbon absorption and the swelling of the elastomer are balanced. Therefore, by modifying the cross-linking density of the elastomer, it is possible to optimize the sensor performance, by finding the condition where the pressure against the fiber is large enough to surpass the resistance of the optical fiber to be bended and, at the same time, the elastomer absorbs enough solvent to bend the fiber at an optimum level.

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