Comparison of three types of fiber optic sensors for temperature monitoring in a groundwater flow simulator
Sandra Drusová, Wiecher Bakx, Pieter Doornenbal, R. Martijn Wagterveld, Victor Bense, Herman L. Offerhaus
Abstract
Different fiber optic sensors have been used for groundwater temperature monitoring and the question is which one to choose for a particular study. In the field conditions it is sometimes difficult to determine how much error is introduced by the sensor placement technique, packaging or cross-sensitivity between temperature and strain. These factors were studied in a laboratory groundwater simulator during a heat tracing experiment. The performance of three fiber optic technologies was evaluated – distributed temperature sensing, fiber Bragg gratings and continuous fiber Bragg gratings. All sensors had comparable accuracy of around 0.2 °C and resolution smaller than 0.1 °C. Therefore, factors which need to be considered when choosing a sensor for groundwater temperature monitoring are spatial resolution, sampling frequency and possibility to measure absolute/relative temperature. The experiment also showed that strain effects can be introduced even when fibers have a loose tube packaging.