Traceable sea water temperature measurements performed by optical fibers

Abstract

This paper describes a technique to perform traceable temperature measurements of the seawater column and seawater surface, based on optical fiber Bragg gratings. The paper explains the different phases of the work done: design of the optical fibers, its optical and thermal calibration and onsite measurements of the seawater temperature. In the design of these thermometers, special attention was paid to the involved materials in order to prevent any damage of the fibers due to the exposure to such rugged environment. The fibers were subjected to optical and thermal calibration, with the aim to get traceable measurements and reliable uncertainty calculation of the seawater temperature. The fibers were deployed in the Mediterranean Sea and water temperatures were continuously monitored and compared with the most common used thermometer in this environment, CTD, located in the submarine observatory OBSEA.