Reflex optical fiber probe for simultaneous determination of seawater salinity and temperature by surface plasmon resonance

A new high-sensitivity optical reflective probe is reported for the simultaneous measurement of seawater salinity and temperature. A concise interference structure was used for exciting the cladding mode. A nanoscale gold film served as the sensitive detection area to induce surface plasmon resonance (SPR). A photosensitive material (polydimethylsiloxane) was partially coated on the sensitive layer to produce double SPR peaks. The SPR effect model of the optical fiber structure was modified and a complete detection system was constructed. The preparation and structural parameters were optimized to obtain high-quality spectral properties. Through the calibration experiments, the response to salinity at its characteristic wavelength had a sensitivity of 0.0558 nm/%, while the temperature response at its characteristic wavelength was −4.418 nm/°C. The reflective probe was shown to have low crossover sensitivity. Compared with standard instrumentation, this device was shown to be stable and precise and is expected to have significant practical applications.