Theoretical study on simultaneous measurement of seawater temperature and salinity based on dual fiber interferometers combined with nonlinear decoupling algorithm. (April 2023)

• Record Type: Journal Article
• Authors: Liao, Yipeng; Yang, Kaiming; Shi, Xin
• Is Part Of: Measurement. Volume 211(2023)
• Publication Date: 2023-04
• Subjects: Fiber-optic interferometer -- Fiber sensing -- Decoupling algorithm -- Temperature -- Salinity; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2023.112596
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: Dual fiber interferometers is theoretically studied for seawater temperature and salinity measurement. The interference dip and peak positions is quadratic functions of temperature. There is interaction between temperature and salinity. Quadratic polynomial surface fitting is adopted to establish calibration equations. Quadratic polynomial surface-based demodulation algorithm shows high accuracy in comparative study. Abstract: Accurate measurement of temperature and salinity is an important foundation for oceanographic research. In this paper, dual fiber interferometers combined with a novel nonlinear decoupling algorithm is studied theoretically for simultaneous measurement of seawater temperature and salinity. The correlation analysis shows that there is not only a quadratic relationship between the position of interference dips and temperature, but also interaction between temperature and salinity. Therefore, the quadratic polynomial surface fitting method, containing the important interaction term, is used to build the relationship between interference dips position and both temperature and salinity. A quadratic polynomial surface-based nonlinear decoupling algorithm is developed, and the deviation of this algorithm are noticeably smaller than that of the commonly used linear decoupling algorithm. This work may offer useful reference for developing practical optical fiber seawater temperature and salinity sensors and establishing decoupling algorithms for other dual-parameter fiber-optic sensors.