High-sensitivity temperature sensor based on PDMS-coated photonic crystal fiber interferometer

•High-performance and robust fiber optic temperature sensor based on polydimethylsiloxane (PDMS)-coated photonic crystal fiber that can accurately and reliably operate in harsh environments is developed.•The photonic crystal fiber interferometer (PCFI) coated with PDMS film is theoretically simulated and experimentally demonstrated for temperature measurement, with focuses on the effect of length and thickness of the PDMS film on temperature sensitivity.•The temperature sensitivity of proposed PCFI is improved from 5.3 pm/°C to −0.17 nm/°C by employing the PDMS film.•Temperature-strain cross-sensitivity of PDMS-coated PCFI is negligible (∼0.01 ℃/με).