High-sensitivity temperature sensor based on anti-resonance in high-index polymer-coated optical fiber interferometers

Compared to the multimode interference (MMI) effect, the anti-resonance (AR) effect does not rely on the multimode property of the optical waveguide. This Letter shows that fiber bending can suppress the MMI and can break the superposition of AR spectra of multiple modes in a high-index polymer-coated optical fiber interferometer based on a single-mode fiber—polymer-coated no-core fiber—single-mode fiber hetero-structure. This results in the dominance of the AR spectrum of an individual mode and consequently in periodic sharp transmission dips. As a result of this phenomenon and large thermo-optical and thermal expansion coefficients of the polymer, a compact, high-sensitivity and linear response temperature sensor with the sensitivity as high as −3.784 nm/^◦C has been demonstrated experimentally.