Improvement of Sensitivity in Plastic Optical Fiber Gasoline Leakage Sensors

Optical fiber sensors for detecting leakage of gasoline have been studied. When exposed to gasoline vapor, certain rubber-type polymers such as polyisoprene cause swelling and their refractive indexes decrease depending on the vapor pressure of gasoline. Based on this effect, the fiber-type sensor heads were fabricated by coating the swelling polymer as a cladding layer on the fiber core with slightly lower refractive index than that of cladding. This sensor head changes its fiber structure from leaky to guided, and then, change in the transmitted light intensity by leakage of gasoline can be observed. The improvement of sensitivity in a wide range of gasoline vapor pressure was attempted.