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 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 these environment, CTD, located in the submarine observatory OBSEA. This paper is part of a Special Issue entitled VSI: 2017 IMEKO TC 19. Research Highlights  A technique, based on fiber Bragg gratings (FBG), to measure traceable seawater temperature was developed  Design, characterization together with the optical and thermal calibration of the FBG was performed  Onsite seawater temperature measurements and its continuous monitoring by using FBG were performed in the Mediterranean submarine observatory OBSEA Abbreviations CTD, device to measure conductivity, temperature of the seawater and depth; FBG, Fiber Bragg Grating; OBSEA, underwater observatory (www.obsea.es); Pt-100, platinum resistance thermometer with a value of 100 Ω at the triple point of water; Pt-25, platinum resistance thermometer with a value of 25 Ω at the triple point of water

Application of Fiber Bragg Grating Sensor Technology to Leak Detection and Monitoring in Diaphragm Wall Joints: A Field Study

“…A narrow range of wavelengths is reflected from a sensor when it is illuminated by broadband light from the demodulator. The light reflected is sent to the demodulator device, which determines the temperature along the length of the detection tube, thus tracking the temperature of the wall joint [ 26 , 28 , 29 ].…”

Review of Optical Fiber Sensors for Temperature, Salinity, and Pressure Sensing and Measurement in Seawater

“…By comparing the measured results with CTD (YRS1-1), measurement accuracy better than 0.2 °C was obtained. In 2017, C. Garcia Izquierdo et al also demonstrated a distributed temperature sensor monitoring system, in which an FBG was written into the single-mode fiber coated with acrylates (SM-ITU652) [ 144 ]. To enhance its environmental adaptability, the fiber-optic sensor was encapsulated in a 316L stainless steel tube with a seawater-resistant (polypropylene/PEEK) coating.…”

The MeteoMet2 project—highlights and results

“…A new technique to perform traceable temperature measurements in seawater was studied, designed, developed and tested in field by CEM, CSIC and UPC [24,25]. The thermometers consist of several FBGs installed at different points along the optical fibers.…”

“…A new technique to perform traceable temperature measurements in seawater was studied, designed, developed and tested in the field by CEM, CSIC and UPC [24,25].…”

“…The bath shows a stability and uniformity of 35 mK in the calibration range (0-30) °C of the CTDs. A calibration procedure was developed with a complete calibration uncertainty model [26].…”