High-sensitivity and fast-response fiber-optic micro-thermometer based on a plano-concave Fabry-Pérot cavity filled with PDMS

•The sensor obtains a high temperature sensitivity of 1.509 nm/°C due to the thermal expansion effect of PDMS.•The geometrical optics model and wave optics model of the plano-concave Fabry-Pérot cavity are first given in this paper.•The total length of the sensor is only 120 μm.