In this paper we discuss the stability and effectiveness of an optical fiber sensor for CO2 phase monitoring that could be used inside pipelines, rock caverns and steel tanks for Carbon Capture and Storage (CCS) systems; in Enhanced Oil Recovery (EOR) processes; and in mapping of natural reservoirs. The sensor is an optical fiber refractometer and is shown to be capable of identifying phase changes and when two-phase systems co-exist, even near the phase transition line. When properly calibrated, the sensor can be used to obtain the refractive index and density (calculated with the Lorentz-Lorentz formula) of CO<sub>2</sub>.
A refractive index sensor based on the Fresnel reflection at the tip of a single mode optical fiber is used to study phase
changes of CO<sub>2</sub> when cooled down from room to -50° C. The sensor system is compact and can be readily integrated into
other optical and electronic systems. The refractive index measurements present good agreement with the literature. The
use of the refractometer as a tool to determine the CO<sub>2</sub> phase in oil fields is envisaged.
A magnetic field sensor comprised of a high birefringence photonic crystal fiber coated by a Terfenol-D/Epoxy
composite layer is proposed. Magnetic fields induce strains in the magnetostrictive composite that are transferred to the
fiber interfering with light propagation. The sensitivity of the developed sensor with magnetic fields is measured to be 6
A simple interrogation system for semi-distributed fiber Bragg grating (FBG) sensor array with a tunable pulsed laser is
demonstrated. The pulsed light source is used to discriminate, in space or in time, the FBG position. The sensor array can
then be constituted with low reflectivity FBG (<5%) and with the same wavelength (the FBGs have to be spatially
separated). This improvement increases the capacity of the tunable pulsed laser system interrogation, which can reach up
to 1000 sensors in one single fiber. The signals are measured with only one photodetection system, which makes
detection less dependent of intensity variations and minimizes external influences on the circuit, such as variations in the
environment temperature. A test approach has been assembled for the interrogation of five sensors in the same fiber,
varying its reflectivity from 0.8% to 1.6% and with the same nominal wavelength.