High-sensitivity salinity measurement sensor based on no-core fiber

A compact, stable, low cost and high sensitivity fiber salinity sensor based on single mode fiber-single mode fiber-no-core fiber-single mode fiber-single mode fiber (SSNSS) structure is proposed and demonstrated. It is proved by experiments and simulations that the sensor has high sensitivity to external refractive index (RI) changes, so as to achieve the purpose of gauging the seawater salinity. When the RI of surrounding media in sensing area changes, the absolute value of sensitivity for the refractive index measurement can be above 16,000 nm/refractive index unit (RIU) that is higher than other fiber salinity sensors as we known. In the experimental study, a fiber salinity sensor with the sensitivity of up to -3.42 nm/‰ was achieved when the salinity varied between 0‰ and 40.001‰, and the sensor showed a good linear response.