High-resolution silicon-based optical Fabry-Perot sensing system for seawater temperature measurement

This paper presents a high-precision temperature sensing system for in-situ monitoring of the deep-sea environments. The system utilizes a silicon-based Fabry-Perot interferometer as its sensing probe and employs a current-modulated distributed feedback laser to generate a linearly periodic wavelength-varying light source. The absorption line of H13C14N gas cell is used as a reference for real-time laser wavelength calibration. Laboratory test results indicate that the sensor has a sensitivity of 75 pm/°C and a resolution of 6.2×10-5°C with a dynamic range of 0 to 35°C. A watertight and pressure-resistant packaging structure was designed and fabricated, capable of enduring hydrostatic pressures up to 115 MPa, as verified through laboratory-simulated pressure tests, thus guaranteeing the system's adaptability to deep-sea environments. Field tests were conducted in the South China Sea, encompassing both short-term profile tests and long-term bottom-sitting tests, with comparative experiments performed against an SBE37 Conductivity-Temperature-Depth (CTD) sensor. The test results demonstrated consistent temperature measurement details between the sensor and the CTD, exhibiting excellent long-term stability and reliability. The system features a simple structure, high resolution, rendering it a promising tool for oceanographic research, resource exploration, and deep-sea environmental monitoring.