A Fiber-Optic Sensor Using an Aqueous Solution of Sodium Chloride to Measure Temperature and Water Level Simultaneously

Abstract

A fiber-optic sensor system using a multiplexed array of sensing probes based on an aqueous solution of sodium chloride (NaCl solution) and an optical time-domain reflectometer (OTDR) for simultaneous measurement of temperature and water level is proposed. By changing the temperature, the refractive index of the NaCl solution is varied and Fresnel reflection arising at the interface between the distal end of optical fiber and the NaCl solution is then also changed. We measured the modified optical power of the light reflected from the sensing probe using a portable OTDR device and also obtained the relationship between the temperature of water and the optical power. In this study, the water level was simply determined by measuring the signal difference of the optical power due to the temperature difference of individual sensing probes placed inside and outside of the water. In conclusion, we demonstrate that the temperature and water level can be obtained simultaneously by measuring optical powers of light reflected from sensing probes based on the NaCl solution. It is anticipated that the proposed fiber-optic sensor system makes it possible to remotely monitor the real-time change of temperature and water level of the spent fuel pool during a loss of power accident.

A Simple All-Optical Water Level Monitoring System Based on Wavelength Division Multiplexing with an Arrayed Waveguide Grating

“…Moreover, it is not easy to operate the level meter during a loss of power accident. To overcome these limitations, there have been several approaches to apply an optical fiber sensor (OFS) to nuclear facilities, due to its advantages such as passive sensing capability, remote transmission, EMI-tolerance, radiation-resistance and redundancy [5,6,7,8]. Specifically, many studies have been done with the various types of optical sensing techniques to monitor important physical parameters under harsh environments such as neutron and gamma radiation [8,9,10,11,12].…”

“…Specifically, many studies have been done with the various types of optical sensing techniques to monitor important physical parameters under harsh environments such as neutron and gamma radiation [8,9,10,11,12]. For the water level measurement, there have been reported a number of quasi-distributed optical fiber sensors based on several multiplexed sensing techniques [6,7,13,14,15,16,17,18]. The multiplexing schemes are divided into two categories according to the sensor types: (1) discrete level sensors with an optical coupler, or (2) special fiber sensors that embedded several discrete level sensors on a single fiber.…”

A New Water Level Measurement Method Combining Infrared Sensors and Floats for Applications on Laboratory Scale Channel under Unsteady Flow Regime

“…Fiber optic. Fiber optical sensors have recently been used to detect water depth and temperature [6,7,8,9]. They are used in many domains such as the oil and gas industry, marine applications, and biomedical applications.…”

Increasing the Sensitivity of an Optic Level Sensor With a Wavelength and Phase Sensitive Single-Mode Multimode Single-Mode Fiber Structure

“…In this sense, a wired technology is proposed here, which consists of tracking the light variations inside an optical fiberbased structure. Fiber-optic-based devices present interesting properties such as immunity against electromagnetic interferences, possibility of multiplexing of sensors and small size, combined with the fact of being resistant to hazardous or inflammable media, which is interesting in order to make this technology versatile in many applications [10], [11]. The most recent optical approaches to liquid level sensors suggest an indirect measurement of the liquid level by studying the effect of pressure in the device [12], or a direct measurement by analyzing the wavelength shift when part of the device is introduced in liquid (long-period fiber gratings and interferometers can be used [13,14]).…”