A two-core photonic crystal fiber (TC-PCF) based highly-sensitive temperature sensor
was proposed and demonstrated. By selectively infiltrating the central airhole with refractive index
liquid (RIL), a three-parallel-waveguide structure was formed. A dual-component interference
pattern, consisting of a large spectrum envelope and fine interference fringes, was observed in
the transmission spectrum. The simulation results confirmed that the interference was arising
from a few hybrid supermodes in the fiber coupler structure. They were in good agreement with
the experimental observation on the discrete temperature windows with different temperature
sensitivities due to couplings between different hybrid supermodes in respective temperature
windows. By tracing the wavelength shifts of the large spectrum envelope, high sensitivities were
achieved at 42.621 nm/°C in the temperature range from 54.2 °C to 55 °C and 32.159 nm/°C
from 51.8 °C to 52.6 °C.
This work was supported by the Ministry of Education - Singapore, Academic Research Fund
Tier 1 (MOE2019-T1-001-111). We thank the Yangtze Optical Fibre and Cable Joint Stock
Limited Company (YOFC) for providing the TC-PCF.