Fast-Response Temperature Sensing Using Dual-Wavelength Differential Cross Multiplication for Interrogating Fiber-Optic Fabry–Pérot Interferometers

This article proposes a novel demodulation approach for fast measurement of seawater temperature, utilizing the dual-wavelength differential cross-multiplication (DWDCM) algorithm. The system employs a silicon cavity-based Fabry–Pérot interferometer (FPI) as the temperature sensing element, demonstrating the effectiveness of DWDCM demodulation for high-frequency temperature monitoring. A theoretical analysis was conducted to optimize the selection of two laser wavelengths used in the DWDCM system, ensuring compatibility with the seawater temperature measurement range and laser wavelength shift tolerance. Experimental results demonstrate that the FPI temperature sensor exhibits high-temperature accuracy and fast response. The maximum positive and negative temperature difference between the FPI sensor and the high-precision platinum resistance thermometer (PRT) are 0.0046 °C and −0.0036 °C, respectively, with a rapid response time constant of 6.0 ms. These results underscore the sensor’s capability for precise monitoring of dynamic temperature variations with high temporal resolution, while also offering the advantages of reduced data storage requirements and simplified data processing. This is particularly beneficial for long-term oceanic turbulent temperature measurements on mobile marine platforms, such as autonomous underwater vehicles (AUVs) and profiling floats.