Fiber-Optic Anti-Resonance and Interference Effect Superimposed Sensor for Simultaneous Measurement of Temperature and Salinity With Low Crosstalk

Anti-resonance (AR) is a special optical resonance phenomenon developed in the past decade, which has been researched for telecommunication networks, supercontinuum lasers, and sensing due to its low loss, broad tunable range, and high sensitivity. Here, a novel seawater temperature and salinity simultaneous measurement sensor with remarkable sensitivity and low crosstalk is demonstrated using the superimposition of AR effect and Mach–Zehnder interference. The AR is excited by a temperature-sensitive material-filled hollow core tube fiber (HCTF), while the interference is formed by a single-mode fiber (SMF) with a transverse penetration channel. The simulation analysis and experimental test results indicate that the characteristic dips of AR and interference structures coexist in the spectral curve. According to the wavelength position of the characteristic dips, and combined with the polynomial surface decoupling algorithm to reduce crosstalk between measured parameters, the sensor realizes the temperature and salinity sensing with the minimum sensitivities of 1.825 nm/°C and −2.584 nm/‰, respectively. The technique uses commercial fiber-optic components to make a cost-effective all-fiber probe with compact structure, good stability, and excellent processing consistency for reliable seawater parameters’ measurement.