Temperature-insensitive high-sensitivity refractive index sensor based on a thinned helical fiber grating with an intermediate period

A temperature -insensitive high -sensitivity refractive index sensor is proposed and experimentally demonstrated, which is based on utilization of a thinned helical fiber grating but with an intermediate period (THFGIP). Attributed to the reduced diameter and an intermediate period of the grating, the proposed sensor has a high surrounding refractive -index (SRI) sensitivity and a low temperature sensitivity. The average SRI sensitivity of the proposed sensor is up to 829.9 nm/RIU in the range of 1.3410-1.4480 RIU. Moreover, unlike the traditional sensitivityenhancement method by increasing the waveguide dispersion factor, here the waveguide dispersion factor at the resonant wavelength was decreased by reducing the diameter of the fiber grating and as a result, the crosstalk effect due to the temperature change can be further suppressed. The proposed temperature -insensitive SRI sensor has the superiorities of simple structure, ease fabrication, and low cost, which could be found more potential applications in the SRI sensing fields. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement