Negative axicon tip micro-cavity with a polymer incorporated optical fiber temperature sensor

Abstract

A negative axicon micro-cavity polydimethylsiloxane (PDMS) filled Fabry-Perot interferometer (FPI) based sensor for accurate temperature sensing is proposed and demonstrated. The micro-cavity lengths of 130 µm, 160 µm, 240 µm and 260 µm are employed for temperature sensing from 27 °C to 80 °C. The sensing probe responses were measured in terms of wavelength shift resulting from the thermo-induced change in the FP cavity length and in the refractive index of the PDMS filled in the cavity. However, the effect of thermal expansion/contraction of PDMS is found to be more dominating over the change in its refractive index. The highest and least sensitivity of the order of 59 pm/ °C and 24 pm/ °C are observed for 130 µm and 260 µm cavity lengths. The linear relationship between the change in spatial frequency and cavity length with respect to temperature variation are also studied. These miniaturized and stable sensor probes are capable of measuring small change in temperature variation with high accuracy and sensitivity and can be used for remote sensing measurements.