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

Temperature measurement is an essential parameter to be monitored in various industrial, medical, and environmental applications. Developing high-performance and robust fiber optic sensors that can accurately and reliably operate in harsh environments is a challenge. Here, a photonic crystal fiber interferometer (PCFI) coated with polydimethylsiloxane (PDMS) film is theoretically simulated and experimentally demonstrated for temperature measurement. According to the simulated and experimental results, the influence of PCF's length and PDMS film's thickness on temperature response is little. Compared with bare PCFI (2 cm PCF) with temperature sensitivity of 5.3 pm/°C, the temperature sensitivity (-0.17 nm/°C) of the proposed PDMS-coated PCFI is improved by 32 times. Furthermore, the strain sensitivities of PDMS-coated PCFIs with 1, 2, and 3 cm PCF are only −1.15, −1.88, and −1.21 pm/με, respectively. Therefore, the temperature-strain cross-sensitivity of PDMS-coated PCFI is negligible (∼0.01 ℃/με). Besides, the proposed temperature sensor has good reversibility, repeatability, stability, and property of strain-insensitive, which has potential applications in harsh environmental monitoring.