Optical fiber sensor based on SPR and MZI for seawater salinity and temperature measurement

Simultaneous detection of seawater salinity and temperature is conductive to study the state of seawater more intuitively. In this manuscript, a sensor for seawater salinity and temperature simultaneous measurement based on surface Plasmon resonance (SPR) and Mach-Zehnder interference (MZI) is put forward. The sensor forms MZI by fusing multimode fiber at both ends of hollow core fiber, SPR is formed by gold plating on one side of the hollow core fiber, and then MZI and SPR are coupled in a sensing structure. Experimental results reveal that the sensitivity of seawater temperature is −316.72 pm/℃ with temperature changing from 20 ℃ to 45 ℃, and the sensitivity of seawater salinity is 429.72 pm/‰. The proposed sensor overcomes the measurement error caused by the spatial position difference of cascade sensors, and provides a new idea for double parameter detection. What’s more, the sensor presents the advantages of small volume, simple fabrication and excellent performance.