Distributed fiber optic sensor for liquid hydrocarbon detection

A distributed fiber optic sensor for the detection and location of hydrocarbon fuel spills is presented. The sensor is designed such that liquid swelling polymers transducer their swelling into a microbend force on an optical fiber when exposed to hydrocarbon fuels. Interrogation of the sensor using standard Optical Time Domain Reflectometry techniques provides the possibility of rapidly detecting and locating target hydrocarbon fuels and chemicals at multiple positions along the sensor length. Events can typically be located to a precision of 2 m over a 10 km sensor length. Sensor response time on exposure to the hydrocarbon fuel is within 30 seconds. A detailed explanation of the operational characteristics of the sensor and the underlying technology utilized in its operation is given. Experimental tests using prototype sensors to simultaneously detect three separate 50 centimeter-long events are described. The characteristics of the sensor response in a range of hydrocarbon fuels under varying environmental conditions were investigated. Some of the safety advantages in using the sensor and its practical implementation in continuous monitoring of pipelines or fuel containment vessels are discussed.