Highly sensitive photonic crystal fiber salinity sensor based on Sagnac interferometer

For a sensor, high sensitivity, structural simplicity, and longevity are highly desired for measurement of salinity in seawater. This work proposed an ultrahigh sensitive photonic crystal fiber (PCF) salinity sensor based on the sagnac interferometer (SI). The propagation characteristics of the proposed PCF are analyzed by the finite element method (FEM). The achieved sensitivity reaches up to 37,500 nm/RIU and 7.5 nm/% in the salinity range from 0% to 100%. The maximum resolutions of 2.66 × 10−06 RIU and 1.33 × 10−02% are achieved with high linearity of 0.9924 for 2.20 cm length of the proposed PCF. Owing to such excellent results, this proposed sensor offers the potential to measure the salinity of seawater.