Adriana Lúcia Cerri Triques

Simultaneous measurement of temperature and pressure using single fiber Bragg grating and fixed filter demodulation technique

Fiber Bragg grating (FBG) sensors offer many advantages for monitoring strain and temperature, other physical parameters can be measured through the use of mechanical transducers. However, FBGs are sensitive to strain and temperature and, in many cases, it is difficult to discrminate both measurements. To overcome this problem several techniques have been proposed, most of them employing more than one grating. This work demonstrates the possibility to discriminate temperature and pressure measurements using only one FBG sensor and a low cost demodulation technique based on two fixed filters. A pressure transducer has been used to transfer a lateral force to the fiber, proportional to the applied pressure, generating birefringence in the Bragg grating. The system allowed to measure pressure in the range of 0 to 400 psi with uncertainty of 4 psi and, simultaneously, measure temperature in a range of 22°C with uncertainty of 0.1°C.

Fiber Bragg grating sensing for indirect evaluation of corrosion in oil and gas facilities

Corrosion control in pipelines and wells is a critical issue in the oil industry. In this paper, we present an optical fiber sensing technique devoted to monitor one of the parameters involved in corrosion: the environment acidity. In the proposed technique, a transducer mechanically couples a fiber Bragg grating to a pH sensitive hydrogel. The possibility of determining pH values with resolution of 10-2 in a range from 3 to 6 is evaluated and discussed.

Operation of Optical Fiber Sensors in Hydrogen-Rich Atmosphere

The application of optical fiber sensors in hydrogen rich atmospheres and temperatures as high as 300 °C is presented and discussed. Two well known optical fiber sensor technologies are evaluated: (1) distributed temperature sensing, based on Raman scattering, and (2) fiber Bragg gratings. Results show that a new generation of gratings and possibly of fibers that are more hydrogen resistant, both optically and mechanically, are needed.

Mechanical Characterization Using Optical Fiber Sensors of Polyester Polymer Concrete Made with Recycled Aggregates

The sustainable management of solid wastes encourages metallurgic and metal-mechanic industries to look for safety applications for their wastes, thereby attenuating the environmental impact or lowering the costs. The study herein proposes strain monitoring the recycling of foundry sand with organic pollutants, as inert, in the manufacturing process of polymer concrete using optical fiber sensors. This work also analyzes the compressive strength of polyester polymer concrete made with foundry waste, i.e., recycled foundry sand and polyester polymer concrete made with fresh sand. The foundry sands are contaminated with Sodium Silicate from the mould-making process. Polymer Concrete (PC) is a composite material in which the binder consists entirely of a synthetic organic polymer. Optical fiber sensors present a great deal of potential in monitoring the structural health condition of materials. Experimental results show that the use of the embedded FBG sensor can accurately measure strain, providing information to the operator that the structure is subjected to failure. Multiplexed FBG strain sensors enable measuring strain in different locations by occupying only one tiny optical fiber.

Time-encoded WDM technique for multiple Bragg grating sensors interrogation

This work presents a system for the interrogation of optical fiber Bragg grating sensors based on time domain reflectometry and fixed filters. In this system, filtering is accomplished by fiber Bragg gratings, and a pulsed broadband light source is employed to illuminate the gratings. The spectral informations from the sensors are related to the ratio of two pulse intensities, each from a different filter. The signals are measured with a unique photodetection system, which makes detection independent of intensity variations and minimizes external influences on the circuit, such as variations in the environment temperature. Also, a small number of optical couplers and circulators are needed, so the interrogation system costs per sensor is considerably reduced. A test approach has been assembled for the interrogation of six sensors. Comparisons between experimental results and simulations show a good agreement. Extrapolations indicate that it would be possible to interrogate sensors with spectral variations up to 2 nm, providing uncertainties smaller than 5 pm, which is adequate for multiplexed sensing of temperature in a range of 200°C.

Thermal treatment of fiber Bragg gratings for sensing and telecommunication applications

In this work, we evaluated the performance, at elevate temperatures, of fiber Bragg gratings recorded using high power UV lasers. The evolution of grating wavelengths and reflectivities when fibers were submitted to several thermal cycles was determined. The range of thermal stability of the gratings was found to be suitable for telecommunication and sensing applications.

Investigation on Hydrogen-induced Attenuation in Optical Fibers for DTS Application

We analyze hydrogen-induced attenuation of the pure silica core and conventional fibers subjected to high temperature and hydrogen pressure. Hydrogen-induced attenuation in optical fibers is directly influenced by partial pressure of hydrogen surrounding the fiber

Impact of hydrogen-induced effects on optical fiber Bragg gratings

The effects induced by low and high pressure ingression of hydrogen on UV-written germanium doped silica optical fiber Bragg gratings-at room and high temperature-are studied and discussed. Results show that at elevated temperatures (>150 °C), an immediate and permanent shift of the peak grating reflectivity is induced and proportional to the hydrogen concentration (10 pm/AtmH2), whilst at room temperature most of the grating spectrum changes are transient and mostly reversible.