Optical temperature sensor based on whispering gallery modes

A temperature sensor based on whispering gallery modes is realised, which measures temperatures quasi digitally. No tunable laser is necessary. For this purpose the light of a HeNe-laser is coupled evanescently into an array of polymer resonators. Dependent on the ambient temperature the refractive indices and diameters change and optical resonances are excited if the resonance conditions are met. With five resonators we get a 5-bit intensity code from which the temperature is determined. By using optical fibers for evanescent coupling of light it is possible to guide the resonant light back from the resonator to the detector.