Plastic optical fibre sensor for detecting vapour phase alcohol

New plastic optical fibre sensors for detecting alcohol vapour have been st udied. A certain kind of polymer such as a Novolac resin causes swelling wh en it is exposed to alcohol vapour. This effect produces a change in the po lymer refractive index. Based on this principle, the plastic optical fibre (POF) type sensor head was fabricated by coating Novolac-resin and Novolac/ Fe:SO complex film as a cladding layer on the plastic fibre core. When this sensor head was exposed to ethanol and methanol vapour, the light intensit y passing through the sensor head changed remarkably depending on the vapou r pressure. The sensor response was also found to be fast, stable and repro ducible.