Fiber optic system for distributed detection of liquid hydrocarbons

A fibre-optic system for the detection and location of hydrocarbon fuel spills with 2m accuracy over a total length of 10 km is presented. The sensor incorporates liquid-swelling polymers that transduce their swelling into a force on an optical fibre when activated. The standard Optical Time Domain Reflectometry (OTDR) technique is used to interrogate the sensor, which provides the possibility of locating target hydrocarbon fuels and chemicals at multiple positions along the sensor length. Response time of the sensor after exposure to the activating liquid is typically 30 seconds, dependent on the activating fuel. A brief explanation of the operational characteristics of the sensor and the underlying technology utilised in its operation is given. Swelling characteristics of the sensor polymer material in a range of hydrocarbon fuels and solvents is presented. Experimental test results using prototype sensors to detect simulated fuel spills at separate locations are then described. The ability to replace the polymer with materials that are sensitive to other liquids provides the possibility of sensing many other liquids using the same generic design.