Temperature sensor based on selective liquid-filled twin-core photonic crystal fiber

We experimentally demonstrated a temperature sensor by selectively infiltrating refractive index oil (RIMO) in the central airhole of a twin-core photonic crystal fiber (TCPCF). The light incident in the central liquid core effectively enhanced the power coupling between two solid cores under phase-matching condition over a short coupling length. A large spectrum envelop was extracted by a low pass filter from the transmission spectrum. By tracing the wavelength shifts of the large envelop, the largest sensitivity is 34.561 nm/degrees C within the temperature range from 54 degrees C to 55 degrees C. This ultrahigh temperature sensitivity benefited from the interference between fundamental hybrid supermodes of the RIMO infiltrated structure. While the refractive index (RI) of the central liquid core was decreasing with the increasing temperature, the coupling among two solid cores and the central liquid core can still be observed but with a lower power coupling efficiency, whereas the temperature sensitivity became 19.413 nm/degrees C from 55 degrees C to 58.2 degrees C.