A Simple Fiber Optic Thermal Switch Or Fire Alarm

We describe a simple and inexpensive fiber optic thermal switch which gives an alarm if temperature exceeds a threshold determined by the material at the fiber end tip.The effect is based on the melting of suitable waxes where the back scattering of light vanishes when the critical threshold temperature is reached. The present device has many attractive features: it is uncomplicated, is based on a "solid state effect", is totally dielectric, and has an excellent long term stability.