Sensitivity-enhanced temperature sensor based on PDMS-coated long period fiber grating

A sensitivity-enhanced temperature sensor based on a poly-dimethylsiloxane (PDMS)-coated long period fiber grating (LPFG) has been proposed and experimentally investigated. By embedding the LPFG in a temperature-sensitive elastomeric polymer, the temperature sensitivity of the proposed sensor could be effectively improved by 4 times higher than those of the conventional bare LPFG sensors due to the high thermo-optic coefficient (TOC) of PDMS. It can be found that the temperature sensitivities of higher-order modes are higher than those of lower-order modes by analyzing transmission spectra characteristics of the sensor. Because of LPFG is sensitive to surrounding refractive index (RI), the PDMS-coated LPFG will have a high temperature sensitivities of 255.4 pm/°C in the range of 20-80 °C. Due to the high measurement resolution of 0.078 °C, the sensor is promising to be applied to the fields that high-precision temperature measurement is required.