An optical fiber sensor for salinity and temperature simultaneous detection based on dual SPR effect

Seawater salinity is a fundamental parameter of the marine environment. This manuscript introduces a novel fiber optic sensor utilizing dual SPR effect, which is experimentally demonstrated. The sensor is made by fusion splicing Dual-Hole Single-Mode Fiber (DHSMF) that incorporates two sections of multimode fiber (MMF). A gold film is deposited on one section of the DHSMF to induce the surface plasmon resonance (SPR) phenomenon. One half of the sensing area is coated with polydimethylsiloxane (PDMS) as the thermally responsive material. The other half of the sensing area remains uncoated to generate double SPR phenomenon, the double SPR spectrum is adopted for salinity and temperature simultaneously detection. Experimental results reveals that sensitivity of salinity and temperature are 0.33 nm/‰ and 2.82 nm/°C. Furthermore, the sensor presents superior reversibility and stability. The high performance and compact structure making proposed sensor suitable for detecting seawater salinity and temperature simultaneously.